"COMPOSITE MATERIAL"

Cross-Reference to Related Applications

This Patent Application claims priority from Italian Patent Application No . 102022000017424 filed on August 19 , 2022 , the entire disclosure of which is incorporated herein by reference .

Technical Sector

The present invention relates to a composite material , a method of manufacturing an article and a kit comprising such a composite material .

Background of the Invention

In the field of the production of body panels in composite material , in the Automotive , Railways , Aeronautic etc . industries it is known to overlap a first film, in j argon called " surface film" ( containing a respective resin) in contact with a mould, and behind it to apply successive layers of fibrous reinforcements impregnated (pre-preg) with thermosetting resin matrices , and/or successive layers of thermosetting resin matrix that are more or less reinforced with fibres so as to obtain an intermediate material .

This intermediate material , once laminated on the surface of the mould, is then subj ected to the moulding process which is carried out with the application of a compaction pressure of the di f ferent layers and of an appropriate polymerisation temperature of the matrix ( ces ) . The moulding time , given a speci fic thermal profile , is adj usted on the basis of the chemical-physical characteristics of the thermosetting matrix ( ces ) .

More in detail and purely by way of example , some moulding techniques for thermosetting matrix-based composite materials are reported .

- Moulding with vacuum bag and furnace . With this moulding procedure the reinforcement layers , totally or partially impregnated, are deposited on the surface of the mould, combined with the appropriate auxiliary materials ( aerators , vacuum valve , etc . ) and covered with the plastic film of the vacuum bag . The vacuum bag, once sealed, is connected through an appropriate valve to the vacuum line so that ( a ) the atmospheric pressure , external to the bag, can exert all its force by compacting the layers and (b ) all the air is , at least ideally, removed from the inside of the bag with consequent elimination of air bubbles present between the layers . In fact , these air bubbles , i f not suitably removed, inevitably lead to the formation of voids inside the moulded laminate , constituting elements of weakness and structural fragility of the article . Once the vacuum has been applied and consequently the necessary compaction has been applied between the various layers , the mould is placed in the furnace and heated to a speci fic temperature , on the basis of the characteristics o f the thermosetting resin, by applying an appropriate heating ramp . In this way, it is first achieved the fluidi zation of the matrix that is necessary to adequately wet all the reinforcement and, then, the progressive polymerisation process that leads to the formation of the final article .

- Autoclave moulding . This moulding technique derives from the moulding with vacuum bag . The preparation of the mould, the lamination step of the various totally or partially impregnated reinforcement layers and the preparation and closure of the bag follow in a s imilar way what has been described above . The only di f ference lies in the fact that , while the furnace in which the bag is inserted with the previous technique has in its inside a pressure equal to the atmospheric one , the autoclave allows the application of higher pressures . In this way, the compaction force between the various layers is not limited to that of the atmospheric pressure , about 1 bar, but can be increased considerably up to values that usually reach about 6 bar . This moulding technique , compared to the previous one , although more expensive , allows to obtain better quality moulded components both with regards to aspects relative to the structural strength of the laminate and with regards to aspects concerning the superficial qual ity of the article , a fundamental element for the subsequent painting step .

- Compression moulding . In this case , the mould is formed by two components , the mould and the counter-mould . In a first step, the mould is kept open so that there is space between the two hal f-moulds to introduce therein the reinforcement and matrix layerings . Once the lamination step is ended, the mould is closed by operating the relative press , so as to guarantee an appropriate closure force between the two hal f-moulds and consequently an adequate compaction between the various layers of the laminate . The mould is then suitably heated so as to allow the polymerisation reaction of the matrix to progress .

There are several variants to these moulding techniques and hybrid forms thereof . Again, by way of example , the use of membranes that can replace one of the two hal f-moulds of the compression moulding is mentioned . These membranes , through suitable mechanisms , can be pressuri zed so as to exert a pressure on the laminated layers on the hal f-mould, thus guaranteeing the necessary compaction . Other examples of variants can be easily retrieved in the literature and sector j ournals ( D . Rosato , D . Rosato , Reinforced Plastics Handbook 3 ^rd Ed, 2004 , Elsevier ) .

All these moulding techniques with their variants are used in various industrial fields , including the production of components for motor vehicles , to which the present text makes main reference without , however, limiting the generality thereof .

The activities described above require operators to carry out a long manual lamination process with an obvious impact on the overall production cost . In addition, the articles obtained can present imperfections , especially when they have to reproduce particularly complex shapes . The typical defectivenesses of the laminates can be divided into superficial defects , and therefore already visible sometimes even to the naked eye , and defects present inside the laminate that can be found with appropriate destructive and nondestructive techniques .

Some of the defectivenesses found during the production of composite pieces are reported below by way of example .

- Porosity (pitting) . By this term reference is made to small cavities having dimension smaller than a millimetre ( generally of the order of a tenth of a millimetre ) , which are present on the surface of the component . In general , these pores are attributable to the failure to evacuate the air at the interface between the mould and the first layer of the laminate before the gelation of the matrix during the moulding process . This porosity represents a defect that must be adequately removed during the surface treatment step preparatory to painting . In case of excessive porosity, appropriate additional treatments are unfortunately necessary before being able to proceed with painting with the consequent increase in costs .

- Marking (Print through) . This phenomenon consists of the appearance of the imprint of the underlying reinforcement on the painted surface . This imprint , in the case of a woven fabric, will consist in the weft-warp design, in the case of a multiaxial reinforcement it will consist in the mark of the stitching threads or in the spacing between the individual fibres, etc. This defectiveness, if present, may not be immediately visible after the painting process but only emerge during the life of the component once exposed to the natural atmospheric events. There are regulations regulating appropriate accelerated ageing tests that are widely used by car manufacturers in the qualification step of the materials and of the moulding processes. By way of example, the main international standards, to which the car manufacturers have been inspired for the definition of their reference regulations, are reported below: Standard Practice for Determining the Resistance of Cured Coatings to Thermal Cycling, ASTM D6944-15 (2020) ; Standard Practice for

Xenon-Arc Exposure of Plastics Intended for Outdoor Applications, ASTM D2565-16; Plastics — Methods of exposure to laboratory light sources — Part 2: Xenon-arc 1 amp s, ISO 4892-2:2013.

- Irregular superficial distribution of the resin. Several factors may contribute to generating visible irregularities on the surface of the component, such as, for example, a local increase or decrease in the superficial thickness of the matrix to protect the underlying reinforcement fibres. This may be due for example to the lack of adherence of the first pre-preg layer to the surface of the mould ( typical of the concave areas of the mould) before the gelation of the matrix . In this case , a local thickening of the resin layer to protect the fibres (bridging) can be noted . A second example concerns the presence of wrinkles of the reinforcement layers that can be generated when laminating the various layers . In this case , superficial irregularities with alternating resin-poor zones , which may even leave the fibres uncovered, and zones with resin accumulation can be noted . These irregularities can also occur with changes in chromatic tones due to the dif ferent colour of the matrix and reinforcement .

- Internal porosity - This type of defectiveness consi sts in the presence of cavities inside the moulded piece , localised inside the layers or more commonly between layer and layer . In these cases , the defect can be highlighted by making cuts on the laminate and by performing a crosssection analysis through the aid of an appropriate microscope . Typically these cavities are due to air bubbles remained in the matrix at the time of gelation thereof . This defect , based on the dimensions of the porosities and on the distribution, can also compromise the structural properties of the laminate .

- Dry fibres . This type of defect , which can also be found through the analysis of cross sections of the moulded components , is attributable to the lack of flow of the thermosetting resin inside the reinforcement layers , with consequent formation of zones without matrix . The localised absence of matrix precludes the correct distribution of the stress states inside the component , compromising the structural performance thereof . In principle , the pre-impregnated reinforcements , even before moulding, have a good distribution of the resin in the reinforcement but this does not represent a necessary condition for the purpose of success of the moulded component . However, it is important that the reinforcement portions not wetted by the matrix before moulding are suitably impregnated during the moulding following the resin flows generated during the initial steps of the process . Thanks to these matrix flows , in fact , dry fibre- free laminates can be obtained despite using partially or totally dry fabrics , obviously provided that the overall matrix and reinforcement count is adequately balanced as a whole throughout the entire laminate .

It is appropriate that the defects described above are prevented because the superficial ones would make extremely burdensome the painting processes through the application of special additional recovery treatments while the internal ones could represent points of structural weakness .

Aim of the present invention is that of providing a composite material , a method of manufacturing an article and a kit that allow to overcome , at least partially, the drawbacks of the prior art and are , at the same time , easy and economical to implement .

Summary

According to the present invention there are provided a composite material , a method of manufacturing an article and a kit comprising such a composite material as claimed in the following independent claim and, preferably, in any one of the claims directly or indirectly dependent on the independent claim .

Brief Description of the Drawings

The invention is described below with reference to the accompanying figures , which show some non-limiting embodiment examples thereof , wherein :

Figure 1 schematically shows a section of a composite material in accordance with the present invention;

Figure 2 schematically shows a section of a material with overlapping layers constituted by the material of Figure 1 and a layer of reinforcement material .

Figure 3 schematically shows the shape of the DSC curve in the area of the glass transition temperature ;

Figure 4 schematically shows a template necessary for the preparation of the specimens used for the mechanical tests ( the measurements reported are indicated in millimetres ) ;

Figure 5 is a photograph of the template placed on a composite material 1 during the preparation of the specimens used for the mechanical tests ;

Figure 6 schematically shows a trimming tool ( the measurements reported are indicated in millimetres ) ;

Figure 7 shows the trimming steps of a reinforcement 4 of a specimen of the composite material 1 used for the mechanical tests ;

Figure 8 shows the trimming steps of a surface film of the specimen used for the mechanical tests ;

Figure 9 is a photograph of the specimen of the composite material 1 used for the mechanical tests ;

Figure 10 schematically shows the geometry of a mould used to test the present invention ( the measurements reported are indicated in millimetres ) ;

Figure 11 shows the lamination steps of Test N1 ( configuration A - example 5 reported below) ;

Figure 12 shows the lamination steps of Test N2

( configuration B - example 5 reported below) ;

Figure 13 shows the lamination steps of Test N3

( configuration C - example 5 reported below) ;

Figure 14 schematically shows a typical configuration of mould for autoclave complete with moulding material (prepreg) and vacuum bag with the various auxiliaries and vacuum line ;

Figure 15 shows results of tests carried out with a reference material and described within Example 5 reported below; Figure 16 shows results of tests carried out with a reference material and described within Example 5 reported below;

Figure 17 shows results of tests carried out with an embodiment of a material in accordance with the present invention and described within Example 5 reported below;

Figure 18 is a photograph of a mould used to test the present invention (Example 6 ) ;

Figure 19 contains photographs of three moulded components ;

Figure 20 contains three optical microscope images of the sections performed on the points CSA1 , CSB1 and CSC1 reported in Figure 19 ; and

Figure 21 schematically shows a section of an alternative embodiment of the composite material of Figure 1 .

Detailed Description

In accordance with a first aspect of the present invention, there is provided a composite material 1 ( Figure 1 ) to manufacture articles though moulding . The composite material 1 has a surface film 2 , which comprises a first ( thermosetting) resin formulation having an areal weight up to about 700 g/m ² ; a reinforcement 4 , which consists of an at least partially dry first fibrous material having, taking into account the sole fibrous component , an areal weight up to about 900 g/m ² ; and at least one binder 3 , which binds the surface film 2 to the reinforcement 4 . In particular, the areal weight of the first ( thermosetting) resin formulation of the surface film 2 is measured according to standard ASTM D 3529/D 3529M - 97 ( reapproved 2008 ) .

In particular, the areal weight of the first fibrous material is measured according to standard BS EN12127 : 1998 .

In the present text , "resin formulation" means a formulation comprising a resin (properly so called) and optionally further components in addition to the resin (properly so called) ; "thermosetting resin formulation" means a thermosetting resin (properly so called) and optionally further components in addition to the thermosetting resin (properly so called) . Examples of such further components are ( in addition to the crosslinkers ) : accelerators , tougheners , additives to modi fy the rheology/resistance/wettability, organic and/or inorganic fillers etc . ( and combinations thereof ) .

In the present text , "thermosetting resin" means both a resin provided with a crosslinker and a resin capable of crosslinking i f subj ected to heat .

In some cases , the resin is composed of a combination of more types of resins . Alternatively, the resin is composed of only one type of resin .

Examples of classes of crosslinkers are : aliphatic amines , cycloaliphatic polyamines , aromatic amines , aromatic polyamines , polyamides , polyamidoamines , imidazolines , polyaminoimidazolines, ketimines, enamines, imidazoles, cyanamide, dicyandiamide, ureas, hydrazines, hydrazides, carboxylic acids, carboxylic acid anhydrides, phenolic resins, polysulfides, polymercaptans, boron complexes, quaternary phosphonium salts, ternary sulfonium salts. Particularly useful in the context of the present text are: aromatic amines, imidazoles, cyanamide, dicyandiamide, ureas, hydrazides, carboxylic acid anhydrides, phenolic resins, boron complexes (and combinations thereof) .

In the present text, it is intended by "partially dry" a material that is not completely impregnated with a resin (in particular, with the binder 3) . In other words, the at least partially dry material has at least one part without resin (in particular, the binder 3; more in particular, the binder 3 and an adhesive binder - described in more detail below) .

It has been experimentally observed that such material 1 shows a high drapability (i.e. the ability of the material to be easily deformed in order to adhere and conform to the shape and geometry of the mould) . Through the tests carried out (see the examples reported below) it was observed that the use of the material 1 according to the present invention made it possible to reduce the times and facilitate the production of articles. In addition, the articles obtained were shown to have fewer defects.

It has been hypothesized that these results are due to the fact that at least part of the fibres of the reinforcement 4 , being dry, can be easily replaced during the lamination step to easily conform to the geometry of the mould minimi zing the formation of wrinkles and can also allow the passage ( the evacuation) of the air interposed between the reinforcement 4 and the surface of the mould during the moulding step .

The first fibrous material has fibres that , being dry, are able to move independently of each other, compatibly with the intertwine and/or stitching constraints ; more in particular, such fibres are on the opposite side with respect to the side of the surface film 2 . Typically the fibres capable of moving independently of each other are substantially dry .

The dry fibre content ( or alternatively the degree of impregnation) of the reinforcement 4 may conveniently be expressed in terms of water pick-up (WPU) measurable through the procedure reported in the literature ( Simmons M . et al , WO2013186389 ) . In general , the water pick-up value increases as the percentage of dry fibres present within a given reinforcement increases . It is also possible to identify two limit situations potentially applicable to any type of reinforcement : ( a ) completely dry reinforcement (not at all impregnated) , therefore with 100% of dry fibres , for which the maximum water pick-up value is expected, and (b ) completely impregnated reinforcement , therefore with 0% of dry fibres , in which the water pick-up value typically tends to zero .

Advantageously but not necessarily, the reinforcement 4 has a dry fibre content, expressed as %DF-R4 (based on the formula of Equation 1 - reported below) , greater than about 20%, in particular greater than about 25%, more in particular greater than about 30%. According to some non-limiting embodiments, the reinforcement 4 has a dry fibre content, expressed as %DF-R4, up to about 99.8% (in particular, up to about 99.7%; more in particular, up to about 99.5%) .

It has been experimentally observed that the composite material 1 offers a particularly strong drapability as described in Examples 5 and 6 reported below. The efficacy and the functionality of the composite material 1 are correlated to the percentage of dry fibres of the reinforcement 4 (%DF- R4 ) •

It has been experimentally observed that the water pickup value is greatly influenced by the nature of the fibre and by the type of reinforcement considered (type of weaving, an areal weight, etc.) . Consequently, the WPU measurement of a reinforcement, aimed at evaluating its impregnation level, must always refer to the type of reinforcement itself in the totally dry (i.e. non-impregnated) format.

Purely by way of example, consider the following materials constituted by a dry reinforcement made of carbon fibre and a dry reinforcement made of glass fibre and by the respective prepregs with a thermosetting resin formulation:

- reinforcement CBX250R-CAT - C020250R00A200002 produced and marketed by Selcom S.R.L. - Multiaxial Fabrics (Via della Torre, 17 - 31010 Fregona (TV) Italy) . Such a reinforcement is a composite biaxial fabric as described below: carbon fibre T700SC 12K 50C, fibre weight areal weight — 250 g/m ² , arranged at -45°/ + 45°. The carbon fibre is stitched/knitted with a polyester thread (stitch yarn) at 0° and areal weight of 8 g/m ² , with a chain/pillar knitting type; the fabric is stabilised with the following stabilisation thread at 0°: 136 tex E Glass, areal weight of 7 g/m ² . Overall reinforcement areal weight (all-up mass) 265 g/m ² (in the present text by g/m ² are intended grams per square metre) and overall reinforcement width, 1270 mm.

- Reinforcement VR48 GI6224/1 marketed by GIVIDI Fabrics S.r.l. (Via Giacomo Matteotti, 120, 20861 Brugherio MB, Italy) . This reinforcement is a fabric with VR48 style, intertwine of weave Twill 2x2, composed as described below: glass fibre in warp (type and tex) 3 x EC9 68 1x0, glass fibre in weft EC9 204 1x0 or ECU 204 1x0; the GI6224/1 primer is applied to the glass fibre. The fabric has a number of 7.0 threads per cm in the warp direction and a number of 7.0 threads per cm in the weft direction. The minimum tensile strength in the warp is 310 N/cm, the minimum tensile strength in the weft is 250 N/cm. Overall reinforcement areal weight (all-up mass) 290 g/m ² , reinforcement thickness of 0.23 mm and overall reinforcement width of 1270 mm. - GG250X (T700) -DT150-40 ME (H 127 cm) (code M-PRO19235) is a biaxial fabric impregnated with a thermosetting resin system and has the following characteristics: carbon fibre T700SC 12K 50C, fibre weight areal weight 250 g/m ² , arranged at -45°/+45°. The carbon fibre is stitched/knitted with a polyester thread (stitch yarn) at 0° and areal weight of 8 g/m ² , with a chain knitting type; the fabric is stabilised with the following stabilisation thread at 0°: 136 tex E Glass, areal weight of 7 g/m ² . Overall reinforcement area weight (all-up mass) 265 g/m ² and overall reinforcement width 1270 mm. The reinforcement thus described is impregnated with the resin system DT150; the material has a nominal resin content of 40% by weight and a theoretical moulded sheet thickness of 0.27 mm. The resin DT150 (product manufactured by Delta-Tech SpA) has the following characteristics: maximum achievable DMA tg of 140 °C; processing through curing in vacuum bag in autoclave and compression moulding; 30 days of preservability at 21 °C; average tackiness; chemical nature Thermosetting Epoxy Resin; polymerisation temperature interval from 120 to 150 °C; density of the pure polymerised resin 1.24 g/cm ³ ; average dynamic viscosity, 500-1000 Poise at 60 °C.

- W290T-DT150-40 ME (H 127 cm) (code MW290T0440) is a glass fibre fabric with weaving style twill 2x2, impregnated with a thermosetting resin system and has the following characteristics: glass fibre in warp (type and tex) 3 x EC9 68 1x0, glass fibre in weft EC9 204 1x0 or ECU 204 1x0. The fabric has a number of 7.0 threads per cm in the warp direction and a number of 7.0 threads per cm in the weft direction. Overall reinforcement areal weight (all-up mass) 290 g/m ² and overall reinforcement width, 1270 mm. The reinforcement thus described is impregnated with the resin system DT150; the material has a nominal resin content of 40% by weight and a theoretical moulded sheet thickness of 0.27 mm. The characteristics of the resin system DT150 are similar to those described for the previous material . The following Table 1 reports the experimental water pickup values recorded on each material.

Table 1

Conveniently, the percentage of dry fibres of the reinforcement 4 in the composite material 1 ( % DF-R4 ) can be assessed on the basis of the following mathematical formula (Eq . 1 ) : where WPUR4 is the water pick-up measured on the reinforcement 4 of the composite material 1 ( example values are indicated in the last column of Table 1 for the last two materials ) and WPUDry-R4 is the water pick-up measured on the completely dry reinforcement 4 ( example values are indicated in the last column of Table 1 for the first two materials ) . It should be noted that the determination of the WPUR4 value requires the separation of the reinforcement 4 from the surface film 2 and, as far as possible , from the layer of binder 3 interposed between the surface film 2 and the reinforcement 4 . In this regard, by way of example only, this separation can be made by applying a peeling force on a flap of the surface film 2 and a flap of the reinforcement 4 or, alternatively, according to a procedure suitably identi fied based on the possible variants of the composite material 1 .

The surface film 2 comprises a support 8 of a second fibrous material in particular having an areal weight smaller than about 200 g/m ² ( in particular, smaller than about 100 g/m ² ; more in particular, smaller than about 40 g/m ² ) .

The surface film 2 further comprises a first superficial layer 7 , which defines an outer surface of the composite material 1 and comprises ( in particular, mainly consists of ; more in particular, it is substantially constituted by; more in particular, it consists of ) the first ( thermosetting) resin formulation . The support 8 is arranged between the superficial layer 7 and the binder 3 .

In this way the ease of lamination is increased and it is improved the quality of the surface of the finished article ( the production method of which is described in more detail below) .

According to some non-limiting embodiments, the first superficial layer 7 is mainly constituted by (in particular, consists of) the first (thermosetting) resin formulation.

Advantageously but not necessarily, the first thermosetting resin formulation (in particular, the surface film 2) comprises (in particular, inorganic) fillers dispersed (inorganic fillers dispersed) (in particular, in the superficial layer 7) .

The use of fillers, in particular inorganic fillers, in the first thermosetting resin formulation (in particular, in the surface film 2; more in particular, in the first superficial layer 7) allows to improve the obtaining of homogeneous and regular surfaces on the finished component once moulded.

Alternatively, the surface film 2 (in particular, the first thermosetting resin formulation) is without fillers (in particular, inorganic fillers) .

According to some non-limiting embodiments, the fillers are constituted by (a combination of) inorganic fillers of a different chemical nature, such as for example carbonates, silicates, sulfates, metal oxides, etc. (and a combination thereof) .

According to some non-limiting embodiments, the fillers are between 5% (in particular, 15%) and 60% by weight, relative to the weight of the first (thermosetting) resin formulation of the surface film 2 (in particular, of the first superficial layer 7) .

It has been experimentally observed that, surprisingly, a sufficient presence of fillers inside the first superficial layer 7 makes it possible to reduce the thermal expansion coefficient of the layer itself, making it more stable, and obtaining a reduction in the tendency to the print through effect (see above) .

Advantageously but not necessarily, the fillers have a particle size below 200 microns (in particular, at least 1 micron; more in particular, at least 5 microns) .

The dimensions (particle size) are obtained through successive sievings with sieves with holes having decreasing dimensions (diameters) . The diameter of the holes of the first sieve that does not allow the passage of the particles indicates the dimensions (i.e. diameter) of the particles.

The measurements by means of subsequent sievings are carried out as long as the dimensions (i.e. diameters) of the particles and of the holes of the sieves allow it (in particular, up to a minimum of 0.05 mm) . Below these dimensions (in particular, 0.05 mm) , the dimensions of the particles are measured as average diameter D(v,0.5) measured through a laser granulometer - in particular, using a laser granulometer Mastersizer Microplus Ver. 2.19 (Malvern Instruments® Ltd) .

According to some non-limiting embodiments, the first superficial layer 7 has a thickness that is at least 20% (in particular, up to 99.6%; more in particular, up to 98%) of the overall thickness of the surface film 2 (for the measurement of these parameters see further below in relation to the determination of the position of the support 8) .

In addition or alternatively, the first superficial layer 7 has a thickness of at least 0.01 mm (in particular, up to 0.8 mm) .

Advantageously but not necessarily (Figure 1) , the support 8 is arranged in the area of a surface of the surface film 2 opposite the first superficial layer 7 and facing said binder 3; in particular, the support 8 is (at least partially) arranged in contact with the binder 3.

Alternatively the support 8 is arranged inside the (embedded in the) first (thermosetting) resin formulation. In these cases, the surface film 2 comprises a second layer 9 of the first resin formulation such that the support 8 is arranged between the first superficial layer 7 and the second layer 9 (Figure 21) .

To measure the position of the support 8 inside the surface film 2, the following methodology is followed.

The placement of the support 8 inside the surface film 2 (in particular, of the first thermosetting resin formulation) can be defined through the coordinate system Tf _S along the relative thickness. Consider Tf _S = 0 the interface surface of the surface film 2 bordering the layer of binder 3. Consider Tf _S = 100 the outer surface of the surface film 2 , i . e . the surface opposite the binder 3 , and intended to come into direct contact with the mould . Furthermore , consider as the reference term for the placement of the support 8 its median plane P _m f .

Advantageously but not necessarily, the support 8 of the composite material 1 is arranged with the relative median plane P _m f in the dimension T _S f ranging from 0 to 50 .

The placement of the support 8 is evaluated through an analysis of the section of the composite material 1 performed with the aid of an appropriate microscope . In order not to alter the placement of the support 8 ( second fibrous material ) inside the surface film 2 ( in particular, of the layer of the first thermosetting resin formulation) , it is appropriate to carry out the cut of the composite material 1 , necessary for the creation of the section to be analysed, at a temperature smaller than the glass transition temperature of the first ( thermosetting) resin formulation by at least 30 ° C . In this regard, it is possible to resort to the use of a freezer suitable for reaching this temperature or, alternatively, to the use of liquid nitrogen .

Below is reported the procedure relative to the use of liquid nitrogen :

Cut out a sample of composite material 1 with dimensions approximately 5 x 5 cm with scissors or other suitable instrument ; By using metal pliers , gently immerse the sample into liquid nitrogen contained within a Dewar .

Keep the sample immersed for at least 15 seconds ;

Extract the sample from the liquid nitrogen and immediately divide the sample into two halves , by exerting a clean cut using scissors or other suitable instrument ;

Analyse the newly created internal section with the aid of a suitable microscope ;

It should be noted that a similar sequence can also be applied in case a freezer is used . In these cases , it must be ensured that the sample reaches a condition of thermal equilibrium with the internal temperature of the freezer which must be at least 30 ° C smaller than the Tg of the first ( thermosetting) resin formulation .

Once the section of the material has been obtained, it is analysed by using an optical microscope or, alternatively, a scanning electron microscope ( SEM) .

By following the procedure described above , also the thickness of the first superficial layer 7 can be determined .

According to some non-limiting embodiments , the first thermosetting resin formulation comprises a first thermosetting resin chosen from the group consisting of : epoxy resin, cyanate ester resin, vinyl ester resin, acrylic resin, phenolic resin, melamine resin, urethane resin, siloxane resin, alkyd resin, benzoxazine resin, maleimide resin, furan resin, polyester (and a combination thereof) . Typically, the first thermosetting resin formulation comprises (more precisely, the first resin is) an epoxy resin. In other words, in these cases, the first resin comprises (in particular, is) an epoxy resin.

Advantageously but not necessarily, the first resin formulation comprises at least 40% (in particular, at least 50%; more in particular, at least 60%; even more in particular, at least 90%) by weight, relative to the weight of the first resin formulation, of the first resin. In addition or alternatively, the first resin formulation comprises up to 95% (in particular, 85%; more in particular, up to 40%) by weight, relative to the weight of the first resin formulation, of the first resin.

In some specific and non-limiting cases, the first resin formulation consists of the first resin.

Advantageously but not necessarily, the first thermosetting resin formulation (in particular, the first resin) has in its inside a crosslinker. In some non-limiting cases the crosslinker is chosen from the group consisting of: aliphatic amines, cycloaliphatic polyamines, aromatic amines, aromatic polyamines, polyamides, polyamidoamines, imidazolines, polyaminoimidazolines, ketimines, enamines, imidazoles, cyanamide, dicyandiamide, ureas, hydrazines, hydrazides, carboxylic acids, carboxylic acid anhydrides, phenolic resins, polysulfides, polymercaptans, boron complexes, quaternary phosphonium salts, ternary sulfonium salts (and a combination thereof) .

Particularly useful in the current context are: aromatic amines, imidazoles, cyanamide, dicyandiamide, ureas, hydrazides, carboxylic acid anhydrides, phenolic resins, boron complexes.

According to some non-limiting embodiments, the first (thermosetting) resin formulation has an areal weight of at least about 30 g/m ² (in particular, at least about 120 g/m ² ) . More precisely but not necessarily, the first (thermosetting) resin formulation has an areal weight up to about 600 g/m ² (in particular, up to about 400 g/m ² )

Advantageously but not necessarily, the first thermosetting resin formulation (in particular, the first resin) has a contained viscosity variation following heating and a medium-low tackiness.

In some cases, the second fibrous material has an areal weight of at least about 3 g/m ² (in particular, at least about 10 g/m ² ) .

According to some non-limiting embodiments, the second fibrous material comprises (in particular, mainly comprises; more in particular, is made of) carbon fibres, glass fibres, basalt fibres, natural fibres (e.g., flax) , synthetic fibres (e.g., polyester and/or aramid fibres) . In particular, the second fibrous material comprises (in particular, mainly comprises; more in particular, is made of) synthetic fibres (e.g. polyester fibres) .

According to some non-limiting embodiments, the areal weight of the first (thermosetting) resin formulation is at least about 0.7 times (in particular, at least about 1 time; more in particular, at least about 2 times; even more in particular, at least about 5 times; in particular, up to about 100 times; more in particular, up to about 30 times) the areal weight of the second fibrous material.

According to some non-limiting embodiments, the first fibrous material has, taking into account the sole fibrous component, an areal weight smaller than about 500 g/m ² (in particular, smaller than about 300 g/m ² ) .

More precisely but not necessarily, the first fibrous material has an areal weight of at least about 30 g/m ² and comprises (in particular, mainly comprises; more in particular, is made of) carbon fibres, glass fibres, basalt fibres, natural fibres such as flax, synthetic fibres such as polyester and/or aramid fibres.

Advantageously but not necessarily, the first fibrous material is (a fabric and is) chosen from the group consisting of: woven fabrics, unidirectional fabrics, multiaxial fabrics (optionally stabilised through stitching threads) and nonwoven fabrics (in particular, with fibres stabilised through binder) . In some specific cases, the first fibrous material is a unidirectional fabric or a multiaxial (in particular, biaxial) fabric. In addition or alternatively, the first fibrous material is a multiaxial (in particular, biaxial) fabric.

Note that in the present text by "fabric" is meant both a material containing woven and nonwoven fibres.

The binder 3 comprises (in particular, is) an adhesive binder and is arranged between the surface film 2 and the reinforcement 4.

In particular, the areal weight of this adhesive material is measured according to standard ASTM F2217/F2217M - 13 (reapproved 2018) .

Advantageously but not necessarily, the binder 3 comprises (in particular, is) an adhesive binder, having a glass transition temperature (Tg) smaller than about 20 °C.

It has been experimentally observed that when the adhesive binder has these characteristics it can be sufficiently adhesive (tacky) to be able (even in a small amount) to perform its function of connection between the surface film 2 and the reinforcement 4. In particular, the glass transition temperature is smaller than about 15 °C (more in particular, smaller than about 0 °C) .

In some non-limiting cases, the glass transition temperature is greater than about -80 °C.

Advantageously but not necessarily, the adhesive binder has an areal weight smaller than the areal weight of the reinforcement 4 (in particular, smaller than half the areal weight of the reinforcement 4) . According to some non-limiting embodiments , the adhesive binder has an areal weight greater than 2 % ( in particular, greater than 4 % ; more in particular, greater than 6% ) of the areal weight of the reinforcement 4 .

In addition or alternatively, the adhesive binder has an areal weight smaller than about 300 g/m ² ( in particular, smaller than about 150 g/m ² ; more in particular, smaller than about 60 g/m ² ; even more in particular, smaller than about 30 g/m ² ) .

In some non-limiting cases , the adhesive binder has an areal weight greater than about 5 g/m ² .

According to some non-limiting embodiments , the adhesive binder comprises ( in particular, is ) a second ( in particular, thermosetting) resin formulation, which, in turn, comprises ( in particular, is ) a second ( in particular, thermosetting) resin chosen from the group consisting of : epoxy resin, cyanate ester resin, vinyl ester resin, acrylic resin, phenolic resin, melamine resin, urethane resin, siloxane resin, alkyd resin, benzoxazine resin, maleimide resin, furan resin, polyester ( and a combination thereof ) . In particular, the second resin ( in particular, the adhesive binder ) comprises (more in particular, is ) an epoxy (more in particular, thermosetting) resin .

In some cases but not necessarily, the thermosetting adhesive binder ( the second resin) comprises a crosslinker .

Preferably but not necessarily, the adhesive binder ( in particular, the second resin formulation; more in particular, the second resin) is not crosslinked (in particular, the second resin formulation - more in particular, the second resin - is not crosslinked) .

It has been experimentally observed that, in this way, the composite material proves to be particularly drapable.

More precisely but not necessarily, the adhesive binder (in particular, the second resin formulation; more in particular, the second resin) is without (the second resin is without) crosslinker.

It has been experimentally observed that, in this way, the adhesive binder succeeds in performing its function of connection between the surface film 2 and the reinforcement 4 for a long period of time (in practice, ageing more slowly) .

In particular, in these cases, during moulding, the adhesive binder can harden by exploiting the crosslinker of the first resin formulation (that of the surface film 2) and/or that present in the rear layer 5 (described in more detail below) .

According to some non-limiting embodiments, the binder 3 (in addition to the aforementioned adhesive binder) also comprises a fibrous material (in particular, a fibrous layer) immersed in the adhesive binder. For example, this third fibrous material comprises (in particular, mainly comprises; more in particular, is made of) carbon fibres, glass fibres, mineral fibres (e.g. basalt fibres) , natural fibres (e.g. flax) , synthetic fibres (e.g. polyester and/or aramid fibres) , metal fibres and combinations (mixtures) thereof. In particular, this fibrous material (of the binder 3) comprises (in particular, mainly comprises; more in particular, is made of) synthetic fibres (e.g. polyester fibres) .

Advantageously but not necessarily, the binder 3 (in particular, the adhesive binder) has a connection force (between the surface film 2 and the reinforcement 4) of at least about 0.6 N (in particular, at least about 1.0 N) measured on a sample of about 25 mm X 200 mm.

According to some non-limiting embodiments, the binder 3 (in particular, the adhesive binder) has a connection force up to about 200 N (in particular, up to about 150 N) measured on a sample of about 25 mm X 200 mm.

Advantageously but not necessarily, the binder 3 (in particular, the adhesive binder) has a connection stress (between the surface film 2 and the reinforcement 4) of at least about 0.1 kPa (in particular, at least about 0.2 kPa) .

According to some non-limiting embodiments, the binder 3 (in particular, the adhesive binder) has a connection stress smaller than about 40 kPa (in particular, smaller than about 30 kPa) .

The force and the stress indicated in the present text are measured according to what is described in Example 4.

In accordance with some non-limiting embodiments (as shown in Figure 1) , the binder 3 is arranged between the surface film 2 and the reinforcement 4 so as to form a continuous layer and be homogeneously distributed .

According to embodiments not shown, the binder 3 is distributed heterogeneously ( so that there are , between the surface film 2 and the reinforcement 4 zones without binder 3 ) according to a defined design ( for example forming dots , circles , lines etc . ) or a disordered shape ( random distribution) .

In accordance with a further aspect of the present invention there is provided a method of manufacturing an article . The method comprises a first lamination step, during which the composite material 1 as described above is arranged on a mould ( in particular, such that the surface fi lm 2 is in contact with the mould) , in particular such that the composite material 1 substantially acquires the shape of the mould; a second lamination step, which i s subsequent to the first lamination step and during which a rear layer 5 ( Figure 2 ) is arranged on said composite material 1 in contact with the latter so as to obtain a material with overlapping layers 6 ( see Figure 2 ) substantially having the shape of the mould; and a moulding step, which is subsequent to the second lamination step and during which the material with overlapping layers 6 arranged on the mould i s compressed (pressed - in particular, subj ected to pressure greater than the atmospheric pressure ) and heated . More precisely, during the moulding step, the rear layer 5 and the composite material 1 are compressed (pressed) towards each other . In particular, during the moulding step the material with overlapping layers 6 arranged on the mould is suitably compacted and heated in order to obtain the polymerisation of the thermosetting matrix .

According to some non-limiting embodiments , the rear layer 5 comprises a third fibrous material (which is understood as such and therefore dry without resin components ) and a quantity of a third resin formulation .

In particular, the third resin formulation is thermosetting and comprises ( in particular, is ) a third ( in particular, thermosetting) resin chosen from the group consisting of : epoxy resin, cyanate ester resin, vinyl ester resin, acrylic resin, phenol ic resin, melamine resin, urethane resin, siloxane resin, alkyd resin, benzoxazine resin, maleimide resin, furan resin, polyester ( and a combination thereof ) ; more in particular, the third thermosetting resin comprises a crosslinker .

Advantageously but not necessarily, the fibre content of the material 6 with overlapping layers , expressed as Fibre Volume Fraction ( FVF) ranges from the minimum value of about 20% ( in particular, the minimum value of about 35% ) to the maximum value of about 75% ( in particular, the maximum value of about 65% ) .

Below are reported by bullet points the criteria for evaluating the Fibre Volume Fraction of the ( overall laminated) material with overlapping layers 6 : 1) The surface film 2, in its entirety (resin formulation and support) , must be excluded as a non-structural element;

2) The layer of binder 3 must be considered in the overall calculation, taking into account the relative areal weight as matrix in case it is adhesive binder without fibrous material ( Rleg ) , as combination of resin formulation (R _leg ) and of fibre (F _leg ) in case it is adhesive binder containing a fibrous material .

3) The reinforcement 4, i.e. first fibrous material, must be counted as fibre (F _rinf,4 ) .

4) The rear layer 5 must be counted considering both its fibrous component (F _sp ) and its resin component (R _sp ) . The distribution of the resin component and of the relative fibrous component has no influence on the calculation of the Fibre Volume Fraction.

The FVF can then be evaluated based on the following formula :

Where :

F _leg is the areal grammage of the fibrous material of the binder 3 (where present) , D _fleg is the density of the fibre of the fibrous material of the binder 3 (where present) , F _einf ,4 is the areal grammage of the fibre of the reinforcement 4, D _rinf,4 is the density of the material of the fibrous reinforcement 4, F _sp is the areal grammage of the fibre of the rear layer 5, D _fsp is the density of the fibre of the rear layer 5 , R _leg is the areal grammage of the adhesive binder 3 , D _rleg is the density of the resin formulation of the adhesive binder 3 , R _sp is the areal grammage o f the resin formulation present in the rear layer 5 , D _rsp is the density of the resin formulation of the rear layer 5 .

Where only adhesive binder without fibrous material is present , the term F _leg /D _fleg is to be considered null . In this case , the FVF can then be evaluated based on the following formula :

In case , instead, of an adhesive binder containing a fibrous material , both the terms F _leg /D _fleg and R _leg /D _rleg must be considered in the calculation of the FVF (Eq . 2 ) .

On the basis of these considerations , it is advantageous (but not necessary) that the rear layer 5 , combined with the composite material 1 , of fers an appropriate ratio between the areal weight of the fibre and the areal weight of the matrix such as to place the overall FVF of the entire laminate within the limits indicated above .

By way of example , in the case in which the composite material 1 had an insuf ficient content of resin formulation, such that the FVF of the material with overlapping layers was greater than 75% , then the rear layer 5 should contain an adequate excess of the third resin formulation so as to rebalance the FVF (overall of the laminate) of the material with overlapping layers 6.

The fibrous component of the rear layer 5, third fibrous material, has an areal weight of at least about 100 g/m ² (in particular, at least about 350 g/m ² ; in particular, up to about 2000 g/m ² ; more in particular, up to about 1500 g/m ² ) . The rear layer 5 comprises a quantity of the third resin formulation such as to satisfy the overall FVF of the laminate based on the equation 2 (or equation 3) .

In particular, the areal weight of the fibrous component of the rear layer 5 is measured according to standard ASTM D 3529/D 3529M - 97 (reapproved 2008) .

In particular, the third fibrous material is chosen from the group consisting of: woven fabrics, unidirectional fabrics, multiaxial fabrics (in particular, biaxial fabrics; optionally stabilised through stitching threads) , nonwoven fabrics (and a combination thereof) . More in particular, the third fibrous material is chosen in the group consisting of: woven fabrics and multiaxial (in particular, biaxial) fabrics. Even more in particular, the third fibrous material is a woven fabric.

According to some preferred but non-limiting embodiments, the third thermosetting resin comprises a crosslinker.

Advantageously but not necessarily, the third fibrous material comprises (in particular, mainly comprises; more in particular, is made of) carbon fibre, glass fibre, basalt fibre, natural fibres such as flax, synthetic fibres such as polyester or aramid fibres.

According to some non-limiting embodiments, during the moulding step, the material with overlapping layers 6 is subjected to a compression (pressure) of at least about 1 Kgforce/cm ² (in particular, up to about 150 Kgf _O rce/cm ² ; more in particular up to about 50 Kgforce/cm ² ) .

In some non-limiting cases, the material with overlapping layers 6 arranged on the mould is moulded with vacuum bag (inside which the material with overlapping layers 6 and the mould are arranged) and furnace, by applying a depression inside the bag such that the absolute pressure inside the bag is smaller than 0.5 bar (in particular, greater than 0.001 bar) .

Advantageously but not necessarily, during the moulding step, the material with overlapping layers 6 is inserted inside a furnace whose temperature is at least 50 °C (in particular, up to 200 °C) .

In some non-limiting cases, the material is moulded in autoclave at an absolute pressure of at least 2 bar (in particular, up to 10 bar) .

Alternatively, the moulding step is carried out in the press, by applying a compaction pressure of the layers generally greater than 2 Kgforce/cm ² .

According to a further aspect of the present invention, there is provided a kit to implement the above-described method . The kit comprises the composite material 1 and the rear layer 5 as described above .

Further characteristics of the present invention will become apparent from the following description of some merely illustrative and non-limiting examples .

Example 1

This example describes the reali zation of some binders reported in the following Table 2 , where the values are expressed in parts per cent of resin (phr ) . Table 2

F1-F4 indicate the formulations of four di f ferent binders ( among them alternatives ) that have been prepared and can be used in accordance with the present invention and more precisely : Fl is an epoxy binder without crosslinker ; F2 is an epoxy binder with crosslinker ; F3 is a binder containing rubber (with crosslinker ) ; F4 is a cyanate-ester binder .

Araldite® GY2600 (produced and marketed by Huntsman®) is an unmodified, average viscosity, bisphenol A diglycidyl ether (DGEBA) epoxy resin resulting from the reaction of bisphenol A and epichlorohydrin. The main characteristic of this resin is its low content of hydrolysable chlorine. It offers high mechanical performance and confers a good chemical resistance.

Main properties of Araldite GY2600:

■ Epoxy equivalent weight EEW (ISO 3001) : 184 - 190 g/eq;

■ Viscosity at 25 °C (falling ball, ISO 12058-1) : 12000 - 14000 mPa -s

■ Density at 25 °C (ISO 1675) : 1.17 g/cm3

■ (Visual) appearance: clear liquid

■ Colour (Gardner, ISO 4630) : < 1

■ Epoxy index (ISO 3001) : 5.26 - 5.43 eq/kg

■ Content of chlorine, hydrolysable (VTM 116) : < 170 ppm

Araldite® GT 7071 (produced and marketed by Huntsman®) is a low melting point bisphenol A diglycidyl ether (DGEBA) solid epoxy resin with low to medium molecular weight (type 1) . It is used to produce high-performance coating materials, thanks to its exceptional adhesion to a variety of substrates (e.g. metals, cement, wood, etc.) and chemical resistance. It offers greater flexibility and high impact resistance.

Main properties of Araldite GT 7071:

■ Epoxy equivalent weight (ISO 3001) : 500 - 525 g/eq

■ Softening point (Mettler, DIN 51920) : 77 - 82 °C

■ Density at 25 °C (ISO 1675) : 1.19 g/cm3

■ (Visual) appearance: transparent solid resin ■ Colour (Gardner, ISO 4630) : < 1

■ Viscosity at 25 °C (falling-ball, ISO 12058-1) : 200 - 250 mPa -s - 40% solution in butylcarbitol

HyPox® RA95 (produced and marketed by Huntsman®) is a high viscosity mixture constituted by a butadiene-acrylonitrile elastomer dissolved in bisphenol A epoxy resin. Based on a solid CTBN elastomer, HyPox RA95 combines the functionalities of the epoxy resins with toughness and impact resistance. Compared to the conventional epoxy systems, its use improves resistance to impact, peeling and cutting.

Main properties of HyPox RA95:

■ Epoxy equivalent weight (ASTM D1652-90) : 195 - 210 g/eq

■ CTBN content: 5%

■ Viscosity at 25 °C (Brookfield ASTM D2196-05) : 150 000 - 550 000 mPa.s

■ Colour (Gardner, ASTM D1544-80) : <4

■ (Visual) appearance: Matt amber viscous liquid

Primaset® PT-30 (produced and marketed by Arxada®) is a multifunctional cyanate-ester resin capable of providing a highly crosslinked structure with high thermal stability. If properly polymerised, the resulting Tg may exceed 300 °C. This high performance thermosetting resin is characterised by excellent dielectric and mechanical properties and allows an epoxy-like processing

Primary properties of Primaset PT-30:

■ Viscosity at 80 °C: 300-500 mPa.s Appearance: viscous liquid

Colour: from yellow to reddish

■ Specific gravity: 1.2 g/cm ³

■ Ionic chlorine: <10 ppm

■ Moisture content: <0.5 %

■ Gel-time @200 °C: 70-240 min

Dyhard® 10 OS (produced and marketed by AlzChem®) is a micronized dicyandiamide (DICY) -based crosslinker. The singlecomponent systems containing DICY are capable of crosslinking if exposed to 145-160 °C for 30-60 min. After adequate polymerisation, the DICY-based epoxy systems lead to a very dense polymeric structure, which offers a high thermal and chemical resistance.

Main properties of Dyhard® 100S:

■ Dimensions of the particles 98 %: max. 10 microns

■ Melting point: 209 - 212 °C - no anti-caking agent

■ Anti-caking agent content: max. 1.60%

■ Water content: max. 0.30%

■ Appearance: white powder

Dyhard® UR500 (produced and marketed by AlzChem®) is a micronized bifunctional accelerator based on substituted urea. It is usually used as an accelerator of DICY, allowing a reduction of the polymerisation temperature of the epoxy formulation up to 80 °C. The resulting crosslinked matrix shows a dense polymeric network, characterised by good mechanical performance. Despite its high reactivity, Dyhard UR500 can also be applied as a single crosslinker and latencies of up to 2 months are possible. In addition, thanks to its low enthalpy development during the hardening process, it is particularly suitable for thick laminates reinforced with carbon fibre.

Main properties of Dyhard® UR500:

■ Dimensions of the particles 98 %: max. 10 microns

■ Melting point: min. 180 °C

■ Purity: min. 95.0%

■ Volatiles (105 °C) max. 1.0%

■ Appearance: from white to whitish powder

Manganese (II) acetylacetonate (produced and marketed by Merck®) is a metal complex that can be adopted as a catalyst for the cyanate-ester resins to promote the cyclotrimerization reaction .

Main properties of the manganese (II) acetylacetonate:

■ Appearance: light brown powder

■ Manganese content: 21.0 - 23.0%.

The binder with formulation Fl has high tackiness, viscosity at 50 °C 20 Pa -s and density at 25 °C 1.17 g/cm ³ and was obtained with the following methodology. A quantity of Araldite GY 2600 (60 g) preheated to 50 °C and Araldite GT 7071 (40 g) was introduced in a 250 ml glass beaker, mixed with a spatula and heated in a furnace at 120 °C for 1 hour. The mixture was stirred with a spatula every 15 minutes to ensure complete dissolution of the solid component, obtaining a colourless and clear mixture. The binder with formulation F2 was obtained with the following methodology . A quantity of Araldite GY 2600 ( 60 g) preheated to 50 ° C and Araldite GT 7071 ( 40 g) was introduced in a 250 ml glass beaker, mixed with a spatula and heated in a furnace at 120 ° C for 1 hour . The mixture was stirred with a spatula every 15 minutes to ensure complete dissolution of the solid component . The resulting mixture was cooled to 70 ° C and a quantity of Dyhard 100S ( 8 g) and Dyhard UR500 ( 2 g) was added . The final formulation was then vigorously stirred with a spatula to obtain a homogeneous white mixture .

The binder with formulation F3 was obtained with the following methodology . A quantity of HyPox RA95 ( 80 g) preheated to 70 ° C and Araldite GT 7071 ( 20 g) was introduced in a 250 ml glass beaker, mixed with a spatula and heated in the furnace at 120 ° C for 1 hour . The mixture was stirred with a spatula every 15 minutes to ensure complete dissolution of the solid component . The resulting mixture was cooled to 70 ° C and a quantity of Dyhard 100S ( 8 g) and Dyhard UR500 ( 2 g) was added . The final formulation was then vigorously stirred with a spatula to obtain a homogeneous white mixture .

The binder with formulation F4 was obtained with the following methodology . A quantity of Primaset PT-30 ( 100 g) preheated to 50 ° C and Manganese ( 11 ) Acetylacetonate ( 1 g) was introduced in a 250 ml glass beaker . The resulting mixture was then vigorously stirred with a spatula to obtain a brownish mixture . Example 2

This example describes the methodology for measuring the glass transition temperature (Tg) and determining the Tg for the binders described in Example 1.

Tg values of fresh pure resins were determined by performing DSC measurements from -40 °C to 50 °C under a constant nitrogen flow (50 ml/min) . The analyses were performed on a Mettler-Toledo DSC 1 provided with an autosampler using 40 pl aluminium crucibles with a perforated lid. A quantity of 6-10 mg of fresh resin was used for the analysis. The DSC method applied for the analyses is reported as follows.

Step 1: isothermal at -40 degrees Celsius for 1 minute, under N2 50 ml/min

Step 2: scan from -40 °C to 50 °C, 10 °C/min, under N2 50 ml/min .

The Tg determination was carried out using only the curve of step 2. The scanning temperature interval from -40 to +50 °C was chosen as the glass transition temperature should fall in this region. The glass transition values were determined according to ASTM D3418-15, wherein the Tg is equal to the average value between T1 and T2 as shown in Figure 3.

Note that if the Tg value is smaller than -20 °C, the scanning start temperature may be suitably set below -40 °C to improve the readability and the reliability of the Tg calculation. Purely by way of example, if the value of the glass transition temperature is expected to be around -60 °C, a scanning start temperature of -90 °C can be conveniently used for DSC measurement. Equipment with scanning temperatures starting from -150 °C is used to measure glass transition temperatures below -60 °C.

The Tg measured as described above for the binders of Example 1 are reported in the following Table 3.

Table 3

Example 3

This example describes the manufacture of the composite material 1. The following is used as starting material.

• A surface film FS011-200-20-1260 G (code MF020001200) , which is a commercial product manufactured and marketed by Delta-Preg SpA (Loc. Bonifica del Tronto km 16, 64016 Sant'Egidio alia Vibrata (TE) ) , is a film composed of a resin system and of a support and has the following characteristics: resin FS011, resin areal weight 200 g/m ² , polyester fibre support, support areal weight 20 g/m ² , theoretical sheet thickness 0.15 mm. The resin FS011 (product manufactured by Delta-Tech SpA) has the following characteristics and properties: maximum achievable DMA Tg of 160 °C; processing through curing in vacuum bag in autoclave, vacuum bag in furnace and compression moulding; 30 days of preservability at 20 °C; chemical nature Thermosetting Epoxy Resin; polymerisation temperature interval from 80 to 135 °C; density of the pure polymerised resin 1.48 g/cm ³ ; very high dynamic viscosity; average tackiness.

• A binder with formulation Fl as described in Example 1, which in the following examples is referred to as BINDER1.

• A reinforcement CBX250R-CAT - C020250R00A200002 as described above.

For the manufacture of the composite material, it was proceeded as follows:

- The binder Fl, after preheating to a temperature of 55 °C, was spread through continuous filming process (with rotating rollers at a temperature of 55 °C) on a support (in particular silicone paper) , obtaining a continuous layer of the binder Fl with an areal grammage of 50 g/m ² .

- The reinforcement CBX250R-CAT - C020250R00A200002, previously unrolled, was placed on the continuous layer of the binder Fl through continuous production lines, at a temperature of 40 °C, so as to create a continuous layer of binder on the surface of the reinforcement . This intermediate material is identi fied by the code M-LAB-22035 and corresponds to the description BINDER1- 050/GG250X ( T700S ) (H 127 cm) .

- The composite material thus obtained was laminated at room temperature together with the surface film FS 011-200-20- 1260 G so as to put in direct contact the surface of the reinforcement CBX250R-CAT C020250R00A200002 wetted by the binder Fl with the polyester support of the surface film FS 011-200-20- 1260 G . The resulting composite material 1 was then wound in the form of a roll .

A relevant aspect of the production process of the composite material 1 concerns the coupling of the dry reinforcement CBX250R-CAT with the layer of binder Fl . As explained above , in fact , it is relevant that the binder does not wet all the fibre of the reinforcement , so that the rear layer remains at least partially dry . It is likewise important that a dryness level of the reinforcement CBX250R-CAT is also preserved following the coupling of the intermediate material with the surface film .

Example 4

The composite material 1 , as described in Example 3 , has a suf ficient adhesive stability such that it can be used and handled for lamination operations . In fact , the presence of the binder, thanks to its tacky character, guarantees an adequate adhesion between the reinforcement CBX250R-CAT C020250R00A200002 and the surface film FS011-200-20-1260 G, which would otherwise tend to separate, complicating manual lamination operations.

The present example describes the procedure for the quantification of the adhesion force (connection force) exerted by the binder of formulation Fl between the surface film and the reinforcement CBX250R-CAT - C020250R00A200002, evaluated through dynamometric measurements under sliding conditions of the two layers.

Since the stability of the two layers of the composite material 1 can be influenced by the quantity of binder present, the following two versions characterised by a different areal weight of binder were considered in this example:

- FS011-200-20//BINDER1-017/GG250X (T700) (code M-LAB22046) corresponding to the composite material already shown in Example 3 and having a layer of binder with an areal weight of 17 g/m ² .

- FS011-200-20//BINDER1-050/GG250X (T700) (code M-

LAB22036) corresponding to the composite material already shown in Example 3 and having a layer of binder with an areal weight of 50 g/m ² .

The measurements were performed on 5 specimens for each material (in other words, 5 specimens for material M-LAB22046 and 5 specimens for material M-LAB22036) by using an MTS Insight dynamometer, provided with a 100 N load cell and configured to perform tensile measurements . The applied measurement speed was 2 mm/min . All the measurements were carried out at a temperature of 2011 ° C .

The specimens of composite material 1 necessary for the measurements were obtained using the template schematically represented in Figure 4 ( and photographed in Figure 5 ) . This tool , handcrafted by a mechanical workshop, is constituted by a metal frame 8 mm thick, having external dimensions 300x75 mm, internal dimensions 250x25 mm and two slits of approximately 15 mm in length and 8 mm in depth placed along each internal corner . The preparation of the specimens was carried out at a temperature of 2011 ° C . Each specimen was obtained on the basis of the procedure reported below :

- Place the roll of composite material 1 on a cutting plane and unroll a portion of about 1 linear m, leaving the reinforcement 4 ( the side with the polyethylene ) visible ;

- Take the template ( Figure 4 ) and place it gently over the composite material 1 , without exerting any pressure ( Figure 5 ) ;

- Align the long side of the template parallel to the direction of the visible carbon fibre of the reinforcement 4 , i . e . at 45 ° with respect to the stitching threads clearly visible in Figure 5 ;

- With a suitable tranchet axe , cut out a strip of the sample , tracing the internal sides of the template ; - Remove the template and gently extract the strip of composite material 1 .

- Repeat the previous operations until 5 specimens are obtained, taking care to place the template at least 3 cm away, with respect to the long side , from the area corresponding to the previous specimen .

In the case of use of woven fabrics , stitched unidirectional fabrics , multiaxial fabrics of various kind as reinforcement 4 , the specimen must be aligned to the direction with the highest fibre content , in order to minimi ze the deformation of the specimen itsel f during the dynamometric test before the relative breakage . In other cases , the orientation of the template must coincide with the direction of greater tensile elastic modulus (ASTM D3039-3039M- 08 ) .

Each specimen, once obtained, was suitably trimmed for the creation of the gripping areas , necessary for the coupling of the specimen to the clamps of the dynamometer . In this regard, to minimi ze the incidence of articles , these operations were carried out by using the trimming tool schematically shown in Figure 6 . This tool , handcrafted by a mechanical workshop, is constituted by a thin bent metal sheet about 1 mm thick, on the front side of which and near the lower edge there is a slit . Always on the same side , at a height of 25 mm from the lower edge , there is also a demarcation line , used to check the length of the flap of material to be trimmed . The trimming procedure applied is reported below : - Once the polyethylene layer (protective layer covering the reinforcement 4 ) has been removed from the reinforcement 4 , place the specimen on a cutting plane , with the layer of surface film 2 facing downwards ;

- Place the trimming tool over the specimen at a distance of 2 . 5 cm from the short side ( Figure 7A) ;

- Gently li ft the reinforcement layer CBX250R-CAT- C020250R00A200002 , detaching it from the underlying layer of surface film FS 011-200-20- 1260 G;

- Fold the reinforcement flap onto the front wall of the trimming tool ; check that the position of the edge of the folded flap coincides with the reference line ( Figure 7B ) and make a cut with a tranchet axe , using the lower groove ( Figure 7C-D) ;

- Remove the trimming tool and overturn the specimen, placing the paper layer upwards ;

- Replace the trimming tool over the specimen at a distance of 2 . 5 cm from the short side not yet trimmed ( Figure 8A) ;

- Gently li ft the layer of surface film FS 011-200-20- 1260 G, detaching it from the underlying reinforcement layer CBX250R-CAT - C020250R00A200002 ;

- Fold the flap of surface film on the front wall of the trimming tool ; check that the position of the edge of the folded flap coincides with the reference line ( Figure 8B ) and make a cut with a tranchet axe , using the lower groove (Figure 8C-D) ;

- Store the specimen until the time of measurement, taking care not to place any object above it and not to expose it to temperatures higher than that applied for its preparation.

As shown in Figure 9, each specimen thus obtained is constituted by two gripping areas with dimensions of approximately 25x25 mm, one corresponding to the sole reinforcement (CZ1) and one to the sole surface film (CZ2) , and an overlapping area between the two layers (TZ) with dimensions of approximately 200x25 mm.

The dynamometric measurements were carried out on the basis of the procedure reported below:

- By using an appropriate instrument, measure the dimensions of the overlapping area between the reinforcement layers and surface film, recording two measurements of the width (points MP1 and MP2 of Figure 9) and one for the long side (TZ of Figure 9) ;

- Place the specimen between the clamps of the dynamometer;

- Tighten the clamps on the gripping areas of the specimen CZ1 and CZ2, trying to cover the entire area;

- Start the measurement, recording the sliding force.

In this way, it was possible to record a forcedisplacement curve (stress-strain) for each specimen. The determination of the adhesive force (connection force) exerted by the binder on the two layers of the composite material 1 was carried out by evaluating the maximum force recorded before the irreversible failure of the specimen, corresponding to the absolute maximum of the force-displacement curve . The values recorded on the various specimen of the materials considered in this example are summari zed in the following tables :

Table 4

Table 5

In Tables 3 and 4 the stress indicates the connection stress, which is calculated by dividing the connection force of each specimen by the overlapping area between the layers (expressing the results in kPa) . From the comparison of the two versions of composite material 1, characterised by a different areal weight of the layer of binder 3, they provided a different force value in the test configuration adopted. In particular, with the same dimensions of the test area of the specimen, while in the case of the composite material 1 constituted by a layer of binder of 50 g/m ² a force of about 10 N was recorded, the version with 17 g/m ² provided a significantly lower value of 1.6 N (average value) .

This difference in the sliding force of the layer 2 with respect to the reinforcement 4 is reflected in the adhesive stability of the composite material 1 as a whole. In fact, the version with 50 g/m ² of binder 3 was usable in the moulding processes (as described in the examples 5 and 6 reported below) , preserving its structure during all the processing steps (cutting, lamination on the mould, etc.) . Conversely, the composite material 1 with only 17 g/m ² of binder 3 showed a slightly worse adhesive stability (1.6 N) but still sufficient for the moulding operations. Example 5

A fundamental characteristic of the fibrous materials impregnated with thermosetting resin (prepregs ) concerns drapability, i . e . the ability of the material to be easily deformed in order to adhere and conform to the shape and geometry of the mould . A high drapability of fers , in fact , the advantage of being able to carry out laminations on moulds with complex geometries in a shorter time , reducing the overall production time of the component .

Aim of the present example consists in evaluating the drapability of the composite material 1 with respect to the comparison materials , through the moulding of a laminate according to an appropriate geometry .

The tested solutions di f fer based on the level of impregnation of the reinforcements , their possible prelayering format and the nature , quantity and distribution of the resin matrices . The term pre-layering refers to the practice of j oining two or more layers , whether they are prepregs , resin layers or dry fabrics or a combination thereof , into a single roll . These pre-layered are typically available from prepreg manufacturers .

The moulding can then be carried out by sequentially laminating the distinct layers or the pre-layered materials on the mould . Unfortunately, the loss of drapability of the prelayered systems is a very common fact that has greatly limited their spread . In fact , the increased di f ficulty of the laminator to follow the shapes of the mould results in a greater overall lamination time and/or a lower quality in terms of finishing of the moulded component.

In the present example, starting from different materials, three different mouldings based on three different configurations were performed. In all three cases, however, the order of arrangement and the nature of the fibrous reinforcements are similar.

The test presented in this example was carried out by using the materials reported below which are produced and marketed by Delta-Preg SpA: Material Pl

FS 011-200-20- 1260 G (code MF020001200)

It is a surface film constituted by a resin system and by a support and has the following characteristics: resin FS011, resin areal weight 200 g/m ² , polyester fibre support, support areal weight 20 g/m ² , theoretical sheet thickness 0.15 mm. The resin FS011 (product manufactured by Delta-Tech SpA) has the following characteristics and properties: maximum achievable DMA Tg of 160 °C; processing through curing in vacuum bag in autoclave, vacuum bag in furnace and compression moulding; 30 days of preservability at 20 °C; chemical nature Thermosetting Epoxy Resin; polymerisation temperature interval from 80 to 135 °C; density of the pure polymerised resin 1.48 g/cm ³ ; very high dynamic viscosity; average tackiness.

Material P2 GG250X (T700) -DT150-40 (H 127 cm) (code PGG250B0340)

It is a multiaxial fabric impregnated with a thermosetting resin system and has the following characteristics: the carbon fibre reinforcement, having an areal weight of 265 g/m ² , biaxial weaving style ±45°, first layer with a weight of 125 gsm, fibre T700SC 12K 50C and angle -45°, second layer with a weight of 125 gsm, fibre T700SC 12K 50C and angle +45°, stabilisation thread E glass, polyester stitching thread, chain stitching mode, is impregnated with the resin system DT150; the material has a nominal resin content of 40% by weight and a theoretical moulded sheet thickness of 0.28 mm. The resin DT150 (product manufactured by Delta-Tech SpA) has the following characteristics: maximum achievable DMA tg of 140 °C; processing through curing in vacuum bag in autoclave and compression moulding; 30 days of preservability at 21 °C; average tackiness; chemical nature Thermosetting Epoxy Resin; polymerisation temperature interval from 120 to 150 °C; density of the pure polymerised resin 1.24 g/cm ³ ; average dynamic viscosity, 500-1000 Poise at 60 °C.

Material P3

GG600T (T700) -DT150-38 (H 125 cm) (code PGG600T0038)

It is a woven fabric impregnated with a thermosetting resin system and has the following characteristics: the carbon fibre reinforcement, having an areal weight of 600 g/m ² , type of yarn T700SC 24K 50C, weaving style Twill 2x2, warp 1.80 threads/cm, weft 1.80 threads/cm, is impregnated with the resin system DT150; the material has a nominal resin content of 38% by weight and a theoretical moulded sheet thickness of 0.63 mm. The characteristics of the resin system DT150 are similar to those described for Material P2.

Material P4

FS 011-200-20/GG250X ( T700 ) -DTI 50-40 (H127 cm) (code

MF020200PGG250B001)

It is constituted by the materials 1 and 2 pre-layered in a single roll. In particular, the surface film is represented by FS011-200-20-1260 G (code MF020001200) , corresponding to Material Pl described above. The carbon reinforcement impregnated with thermosetting resin is represented by GG250X (T700) -DT150-40 (code PGG250B0340) , corresponding to Material P2 described above. The lamination provides for the less resinrich side of the surface film FS011-200-20-1260 G (code MF020001200) to be placed in direct contact with the GG250X (T700) -DT150-40 (H 127 cm) (code PGG250B0340 ) .

Material P5

FS011-200-20//BINDER1-050/GG250X (T700) (code M-LAB22036)

Corresponding to the composite material 1 with a layer of binder 3 of 50 g/m ² , already described in detail in Example 3.

The moulding tests were carried out by using a disc-shaped aluminium mould (diameter 180 mm) , characterised by the presence in the centre of a convex paraboloid relief with a height of 31.5 mm (Figure 10) . Before each test, the mould was suitably treated following the procedure described below. The aluminium mould was cleaned with a cloth and a thinner

( acetone ) to remove greases and dusts ; subsequently, the mould was treated with the cleaner Chemiease® Mold Cleaner EZ , produced by Chem-Trend L . P . ( 1445 W . McPherson Park, Howell , Michigan) and constituted by a mixture of solvents capable of removing contaminants and waxy residues from the surface of the moulds .

Subsequently, the release agent Marbocote® PK4 was applied, which i s produced by Marbocote Ltd (Unit 9 , Dalton Way, Middlewich Cheshire , CW10 OHU, United Kingdom) and has the following characteristics : transparent liquid appearance , composition polymeric resin in a mixture of non-chlorinated organic solvents , speci fic weight 0 . 756 g/cm ³ , ideal application temperature between 20-30 ° C, thermal stability 250 ° C, coverage 80- 100 m ² /L, storage time 12 months . In line with the instructions provided by the manufacturer, the Marbocote PK4 was applied with a clean and dry cloth in a homogeneous manner, covering the entire surface of the mould; overall , five coats were applied, awaiting 10 minutes between one coat and the other . After applying the last coat and having observed the complete drying of the film of release agent , the mould was left at room temperature for 60 minutes , in order to obtain a complete cure of the product .

After the mould preparation step, the lamination step of the moulding material was implemented on the mould, reali zing the following three configurations : Test Nl; Configuration A (Figure 11)

The material Pl was laminated in direct contact with the mould (having taken care to laminate the resinrich side in direct contact with the mould Figure 11A) ; The material P2 was laminated in contact with the first layer (Figure 11B) ;

The material P3 was laminated in contact with the second layer (Figure 11C) .

Test N2; Configuration B (Figure 12)

The material P4 was laminated in direct contact with the mould (having taken care to place the side of the surface film FS011-200-20-1260 G (code MF020001200) in direct contact with the mould Figure 12A) ;

The material P3 was laminated in contact with the first layer (Figure 12B) .

Test N3; Configuration C (Figure 13)

The material P5 was laminated in direct contact with the mould (having taken care to place the side of the surface film FS011-200-20-1260 G (code MF020001200) in direct contact with the mould Figure 13A) .

The material P3 was laminated in contact with the first layer, i.e. the material P5 (Figure 13B) .

The preparation of the three configurations was carried out through the following procedure:

■ Prepare for each material (first layer, second layer and third layer) portions of circular shape with a diameter of 220 mm;

■ Starting from the vertex of the relief , spread the first layer on the mould and, trying to avoid the formation of folds , make it adhere well to the flat part of the same ;

■ Spread the second layer on the back of the first layer, making sure that it also perfectly copies the geometry of the mould;

■ I f there is a third layer ( configuration A) , spread it on the back of the second layer making sure that it also perfectly copies the geometry of the mould;

■ Finally, remove the excess of material present at the base of the mould .

At the end of the lamination step for the various configurations , the following terminal moulding operations were carried out , which were common to all the tests set out so far .

MOULDING STEP :

The performance of the moulding step ( Figure 14 ) envisaged using the following auxiliary materials :

■ Vacuum Bag G : Airtech Wrightlon® 600V-LFT , 50 pm

■ Aerator H : Airtech Airwave® N10

■ Release Film I : Airtech Wrightlon® 3900R-SHT , 50 pm

The various operations required for the moulding step were carried out through the following procedure :

■ Place the mould J with the relative moulding material F already laminated on an aerator H (using a support plate L if necessary) ;

■ Cover the mould J with a release film I, taking care to isolate the moulding material F from the contact with the aerator H;

■ Place the package (aerator (H) /mould (J) /moulding material (F) /release film ( I ) /aerator (H) ) in a vacuum bag G;

■ Insert a vacuum valve 0 in contact with the aerator H, taking care not to place oneself above the moulding material F.

■ Seal the bag G with the sealant N;

Pull the vacuum, making sure there are no leaks, to at least -0.95 bar and hold it for at least 3 minutes to check the correct adhesion of the bag G to the shape of the mould J.

Once the operations described above have been ended, the actual moulding step began, i.e. the step of curing the thermosetting matrix of the moulding material. In this regard, the sealed mould was placed inside an autoclave, model AIC 1300X3000 produced by Italmatic Presse Stamp! srl, and subjected to the curing cycle, by applying the following parameters :

■ Heating 2 °C/minute up to 135 °C.

■ Isothermal at 135 °C for 90 minutes.

■ Cooling 2 °C/minute up to 60 °C. ■ Vacuum - 0 . 95 bar for the entire duration of the cycle .

■ Pressure 2 bar/minute up to 6 bar implemented at the beginning of the cycle and maintained at a pressure of 6 bar until the end of the cycle itself .

The particular geometry of the mould used requires a strong drapability of the material to be laminated, in order to obtain a moulded piece without wrinkles and with a good superficial finish . In fact , i f the layer to be laminated has a low drapability, the presence of the relief in the centre of the mould results in the immediate formation of folds during the deposition step of the layers , due to the impossibility of adequately conforming each layer to the peculiar geometry .

The three configurations tested, despite the sequence of the reinforcements being similar, provided a di f ferent behaviour in terms of wrinkles and overlapping defects , detectable both during the lamination step and after autoclave moulding . In particular, already during the deposition step of the various layers on the mould, it was possible to observe the following behaviours :

- Test Nl , Configuration A ( Figure 11 ) : the lamination of the surface film Pl as first layer produced a crumpling of the polyester support ( zones Al , A2 , A3 , A4 reported in Figure 11A) . The subsequent depos ition of the second layer P2 resulted in the formation of very extensive wrinkles (Bl , B2 , B3 , Figure 11B ) , an expression of the low deformability of the material ; a similar result was then also found following the lamination of the third layer P3 (Cl, C2, C3, Figure 11C) .

- Test N2, Configuration B (Figure 12) : the use of the pre-layered material P4, if on the one hand it reduced the number of layers to be laminated, on the other it led to the formation of wide wrinkles (Al, A2, A3, A4, Figure 12A) which subsequently overlapped those generated by the lamination of the second layer P3 (Bl, B2, B3, Figure 12B) .

- Test N3, Configuration C (Figure 13) : thanks to the high drapability of the composite material 1 (P5) it was possible to easily deposit the first layer perfectly following the strict geometry of the mould, without generating any fold or wrinkle (Figure 13A) . The regular surface thus obtained allowed an adequate lamination of the second layer (P3) without finding any wrinkle (Figure 13B) .

The superior drapability and softness of the composite material 1 (P5) is to be attributed to the presence of dry and non-impregnated fibres of the reinforcement 4. In fact, the (at least partial) absence of a resin matrix inside the reinforcement confers an exceptional mobility of the fibres that can therefore deform during the lamination step, offering a high capability of adaptation of the material to the geometry of the mould, albeit complex. Conversely, in the case of the configurations A and B, both based on the use of reinforcements impregnated with thermosetting resin, the presence of the resin matrix inevitably imparts less mobility to the fibres . Consequently, each layer experiences a higher sti f fness during lamination that corresponds to a higher resistance to conforming to the geometry of the mould .

It should be underlined that in a production context of composite pieces , the presence of wrinkles and folds during the lamination step is to be avoided, especially for structural components . In fact , structural weakenings or variations in the thickness of the moulded laminate can be generated more or less marked in the area of these foldings of the reinforcements . Precisely to avoid the formation of these wrinkles , it is often necessary to resort to pre-cut prepreg outlines having smaller dimensions which, on the one hand, impose a longer lamination time , on the other hand, can lead to a structural weakening of the moulded piece compared to the use of continuous layers of larger dimensions .

The di f ferent behaviour observed between the three configurations during the lamination step was also evaluated following the autoclave moulding process . Considering the bagside surface of the moulded pieces , the laminates of the three configurations faithfully reproduced what was obtained after lamination of the third layer . In particular, while configuration A ( Figure 15A) and configuration B ( Figure 16A) showed the presence of considerably marked raised wrinkles (Al, A2, A3, A4 ) , configuration C (Figure 17A) was compact and neat, except for a small wrinkle near the edge (Al, Figure 17A) .

Comparing, instead, the side of the laminate initially in contact with the mould, the differences in terms of superficial defects were more pronounced between the three configurations. In fact, configurations A (Figures 15B and 15ZB) and B (Figures 16B and 16ZB) showed the presence of diffuse porosity in the area of the inner edge attributable to an incomplete contact of the first layer with the mould due to low drapability. In particular, configuration B showed a higher incidence of this defectiveness (Figures 16B and 16ZB) , probably linked to a greater stiffness of the first layer compared to that of configuration A.

A further type of defect found on both configurations was the presence of colour inhomogeneity along the radial direction of the component, resulting in the form of dark lines, as shown by the arrows Bl, B2, B3, B4 of Figures 15B and 16B.

In the case of configuration C (relative to a use of a composite material 1, which is an embodiment of the present invention) , instead, the surface of the moulded laminate was without porosity (Figures 17B and 17ZB) , thanks on the one hand to the high drapability of the composite material 1 (P5) which allowed the contact along the entire surface of the mould and on the other hand to the presence of the dry reinforcement 4 which guaranteed an ef fective air evacuation during the moulding process . In contrast , only radial colour inhomogeneities ( Figures 17B and 17 ZB ) , however less marked than the configurations A and B, were observed .

Example 6

In the production scenario of composite components , one of the most relevant factors contributing to the total production cost of a component is represented by the lamination operations . In this regard, high drapability, combined with adequate tackiness of the material to be laminated, is to be considered necessary in order to reduce lamination times and make the entire production process more competitive .

Aim of present test consists in evaluating the quality of the moulded components and measuring the saving in terms of lamination time of fered by the composite material 1 compared to the traditional materials , using the 3 di f ferent configurations o f moulding material shown in the previous example .

The moulding tests were carried out using a composite mould ( Figure 18 ) , whose geometry, by shape and dimensions , can probably represent a medium complexity component of a body of a motor vehicle . Before each test , the mould was suitably treated following the procedure described below relative to the preparation of the mould .

Similarly to the procedure shown in the previous example , the carbon mould was cleaned initially with a thinner ( acetone ) and then with the cleaner Chemiease® Mold Cleaner EZ .

Subsequently, the pore sealer Marbocote® Mould Sealer was applied which is produced by Marbocote Ltd (Unit 9 , Dalton Way, Middlewich Cheshire , CW10 OHU, United Kingdom) and has the following characteristics : transparent and colourless liquid appearance , aliphatic hydrocarbon composition, flash point <10 ° C, stability of the cured film 250 ° C, coverage 80- 100 m ² /L per coat , type of application rubbing and spreading, storage time 12 months . The use of the pore sealer eliminates the microporosities and the small scratches potentially present on the surface of the composite moulds , providing a smooth and glossy surface . In particular, two coats of Marbocote Mould Sealer were appl ied to the mould 10 minutes apart from each other and finally the mould was placed in the furnace for 10 minutes at 60 ° C in order to obtain complete polymerisation of the product .

Subsequently, the release agent Marbocote® PK4 was applied, similarly to what is reported in Example 5 ; overall , three coats were applied, awaiting 10 minutes between one coat and the other . After applying the last coat and having observed the complete drying of the film of release agent , the mould was left at room temperature for 60 minutes , in order to obtain a complete cure of the product .

After the mould preparation step, the lamination step of the moulding material was implemented on the mould, reali zing the three configurations A, B, C reported in Example 5 on the basis of the procedure detailed above . Subsequently, the autoclave moulding was performed, by applying the curing cycle described in Example 5 .

In terms of quality of the moulded piece , the various tests have provided cured laminates with completely comparable structural characteristics and superficial finishes . More in particular, as shown in Figure 19 , in terms of superficial quality, the three di f ferent moulding tests led to cured pieces having a similar superficial finish, without porosity and with a homogeneous coverage of the surface film .

Similarly, from a structural point of view, as highlighted by the optical microscope analysis of the sections ( crosssection) performed on the points CSA1 , CSB1 and CSC1 of Figure 19 and reported in Figure 20 , a good distribution of the resin matrix between the reinforcement fibres in all three moulded pieces was obtained .

Even in the case of the configuration C based on the use of an embodiment of the composite material 1 ( P5 ) , no presence of dry fibres was highlighted even in the area of the dry reinforcement 4 . This result therefore demonstrated the ability of the resin to flow from the rear reinforcement 5 and ef fectively impregnate all the fibres of the dry reinforcement 4 during the cure .

Ultimately, it can be af firmed that all three tests led to the production of moulded pieces of similar quality and in line with the expectations of the reference industrial context . In terms of lamination time, the three tests provided a differentiated response as per Table 6 reported below:

Table 6

Test N3, thanks to the presence of the composite material 1 (P5) , provided the best result, requiring less "operator's time". In particular, compared to the Test Nl, the reduction by about 58% in the lamination time recorded in Test N3 is to be attributed to a lower number of layers to be laminated and to the higher drapability of the composite material 1 (P5) compared to the material Pl which results in an easier and faster placement of the first layer against the mould. Compared instead to Test N2, in which the number of layers to be laminated is the same as Test N3, the reduction by about 55% in the lamination time is offered by a higher drapability of the composite material 1 (P5) compared to the material P4.

It should also be highlighted that the use of the composite material 1 (P5) allows, in general, to avoid long intermediate air removal (debulking) operations during the lamination step. In fact, depending on the geometry of the mould, in order to minimise the appearance of superficial porosity defects, air removal cycles through the vacuum bag and pump are often essential, which cause a lengthening of the lamination times and loss of production efficiency. In the case, instead, of the composite material 1 (P5) , the debulking operations can be conveniently avoided, consequently obtaining a greater production efficiency with the same superficial quality. In fact, the presence of the reinforcement 4 at least partially not impregnated in the composite material 1 (P5) guarantees an effective medium of evacuation of all the air present between the layers at the time of lamination, which is removed directly in the moulding step.

The moulding process performed for this example is represented by the autoclave moulding. Alternative moulding processes, such as for example compression moulding, differ in the fact that they do not provide for the presence of the vacuum bag. However, the comparison in terms of the lamination times object and main objective of present example still remains valid.

Unless the contrary is explicitly indicated, the content of the references (articles, books, patent applications, etc.) cited in this text is referred to in full herein. In particular, the mentioned references are incorporated herein by reference.