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Technical field of the invention

The present invention relates to a structural multilayer panel, in particular a panel for lining the side walls, roofing and/or walking surfaces of train carriages.

State of the art

Currently, the train carriages, approved for the transport of passengers and goods according to European and American regulations, are mainly manufactured by assembling panels that constitute side walls, roof and floor made of extruded elements in aluminum alloy or in steel alloy.

These materials are well suited for this purpose but have some disadvantages including weight and high thermal conductivity together with low corrosion resistance.

The assembling processes, for example for aluminum alloy constructions, involve the assembly of extruded elements constituting the aerodynamic surfaces of the train, for example the assembly of the roof with the side panels and of the latter with the floor and their subsequent welding by means of automatic processing lines.

Some disadvantages of the panels of the known type are the poor corrosion resistance and the poor resistance to passing flame in case of fire.

Furthermore, the thermal conductivity value of aluminum alloys does not meet the thermal requirements required by manufacturers and therefore requires the use of internal insulators.

A further disadvantage is the weight of the panels, which has a significant impact on the overall weight of the train carriage.

An even further disadvantage of aluminum panels is that they require a coating cover, at least on the side facing the inside of the carriage.

In China and Korea, carriages were built entirely in composite materials using a female mold, carbon and glass fabrics with thermosetting or thermoplastic resins. The composite material panels of the known art are for example made by means of molding processes with pre-impregnated materials and curing processes into large autoclaves that optimize the characteristics of the materials by decreasing the voids inside the laminates.

The limit of the manufacturing processes of composite material panels is essentially their cost.

In fact, the railway market does not have the availability to incur prices higher than those it now sustain for the manufacture of carriages with aluminum or steel alloy.

Summary of the invention

Therefore, the technical problem posed and solved by the present invention is that of providing a structural panel for the construction of walls, and/or walking surfaces, and/or roofing elements of a train carriage that allows to overcome the aforementioned disadvantages with reference to the prior art.

This problem is solved by a structural multilayer panel according to claim 1 .

Preferred features of the present invention are detailed in the dependent claims.

The present invention provides some relevant advantages.

In particular, the specific composition of the elements coupled together to form the panel 100 allows to meet the requirements dictated by the regulations and standards of the railway sector - for example in terms of electrical and/or acoustic and/or thermal insulation - and to guarantee a lightening of the overall structure.

Furthermore, advantageously, the components of the panel are shaped in such a way as to facilitate their assembling operations, thus also facilitating maintenance operations.

A further advantage of the panel according to the present invention is the possibility to facilitate joining between sequentially panels, thus allowing savings in terms of both time and costs in the mounting and assembling phase of the panels used to cover a train carriage. Other advantages, characteristics and methods of use of the present invention will become evident from the following detailed description of some embodiments, presented by way of non-limiting example.

Brief description of the figures

Reference will be made to the figures of the attached drawings, wherein:

Figure 1 shows an exploded perspective view, partially sectioned, of a multilayer panel according to the present invention;

Figure 2 shows a cross-sectional view of the panel of Figure 1 ;

Figure 3 shows a schematic sectional view of a head portion of a train carriage.

Detailed description of preferred embodiments

In the following, the description will be directed to a structural multilayer panel, for example self-supporting, in particular configured for the construction of walls and covering elements of a train carriage.

With reference to figures 1 and 2, a first embodiment of the structural multilayer panel according to the present invention is generally denoted with 100.

The multilayer panel 100 according to the invention, also called sandwich panel, comprises a first covering element 30 made of dielectric material and a second electrically conductive covering element 70.

In particular, the two covering elements 30 and 70 are substantially plate-shaped.

As shown in the figures, a filling element 50 made of expanded material is positioned or positionable between the first covering element 30 and the second covering element 70, in such a way as to isolate the two covering layers from each other, i.e. the two external layers of the panel.

Advantageously, the structural multilayer panel 100 further comprises joining means 15,25; 13,17, 23, 27 configured to allow a coupling between at least one of the aforementioned covering elements 30 and/or 70, and the filling element 50. In particular, the joining means comprises a receiving seat 15 made at at least one thicking edge of the filling element 50 and a protuberance 13, 17 made on a perimeter edge of at least one of the aforementioned first covering element 30 and/or second covering element 70.

In a preferred embodiment, the joining means further comprises an adhesive material, for example a structural adhesive, with an extremely high adhesive power. The adhesive, or glue, in particular polymer-based, is positioned or positionable between each covering element 30, 70 and the filling element 50.

In the preferred embodiment, the receiving seat 15 has a "U" shape.

As shown in the figures, the protuberance 13 made on the perimeter edge of the first covering element 30 is configured and dimensioned to abut in the receiving seat 15, in a coupling configuration between the first covering element 30 and filler element 50, in particular in a shape coupling configuration.

The protuberance 17 made on the perimeter edge of the second covering element 70 is configured and dimensioned to abut in the receiving seat 15 in a coupling configuration between the second covering element 70 and the element filling 50, in particular in shape coupling.

In the preferred embodiment, the conformation of the protuberance 13, 17 on the edge of the covering element 30, 70 provides at least one portion folded to abut with a side wall of the seat 15 formed in the edge of the thickness of the covering element 50.

In the example described here, the joining means comprises a protrusion 25 made at a further thicking edge of the filling element 50, and a protuberance 23, 27 made on a perimeter edge of at least one of the aforementioned first covering element 30 and/or second covering element 70.

As shown in the figures, the protuberance 23 made on the perimeter edge of the first covering element 30 is shaped and dimensioned to abut on the projection 25 of the filling element 50 in a coupling configuration between the first covering element 30 and filling element 50, in particular in a shape coupling configuration. The protuberance 27 made on the perimeter edge of the second covering element 70 is shaped, and sized, to abut on the protrusion 25 in a coupling configuration between the second covering element 70 and the filling element 50.

As shown in the figures, the projection 25 has a complementary shape, of the male-female type, with respect to the receiving seat 15 of the filling element 50, in such a way that even in an assembled configuration of the panel 100, in which the first panel 30 and the second panel 70 are coupled to the filling element 50, at least two peripheral edges of the panel 100 have a complementary shape of the male-female type.

This configuration allows to use a plurality of sequentially panels 100, and to quickly couple them together by means of a male-female coupling, to form walls and/or walking surfaces and/or roofing elements of a train carriage.

Advantageously, the panel 100 according to the present invention has a filling element 50 made of polymeric material, optionally thermoplastic.

In particular, the filling element 50 in expanded material, or core of the multilayer panel 100, has a density value between 30 kg/m ³ and 2000 kg/m ³ , preferably between 30 kg/m ³ and 100 kg/m ³ . In a preferred embodiment, for the realization of the filling element 50, a thermoplastic PET foam material is used, for example Airex T90, with a density value between 30 kg/m ³ and 100 kg/m ³ .

The transverse thickness of the filling element 50 is preferably between a minimum value of about 45 mm and a maximum value of about 100 mm. In particular, the thickness is defined not only on the basis of the stresses to which the panel is subjected, but also on the basis of the systems it must house.

The first covering element 30, made of dielectric material, is used facing the inside of the train carriage, in an assembled condition of the panel 100, and is preferably made of composite material which has a low thermal conductivity, which allows the achievement of the performance required by train manufacturers - in terms of insulation - and which , thanks to a density value between 1.6 and 1.8 gr/cm ³ , allows weight savings compared to structural solutions in aluminum alloy or steel.

Advantageously, the first covering element 30 made of dielectric material allows electrical insulation, thus ensuring perfect electrical insulation of the panel with respect to any short-circuits of the cables passing through the panel, increasing the safety of passengers or the general integrity of the wall or roof of the carriage.

Preferably, the composite material of the first covering element 30 has a glass or carbon fiber reinforcement, for example in the form of fabric, and a thermoplastic or thermosetting polymer matrix, according to the technical requirements dictated by the regulations and in particular depending on the mechanical stresses to which the panel 100 must be subjected during the assembly and use of the train carriage.

Advantageously, the use of a composite material for the construction of the element 30, allows to obtain a finished and pleasant aesthetic appearance without therefore necessarily requiring the application of additional covering layers on the interior of the train carriage.

The covering element 30 made of composite material is preferably made by means of a pultrusion process, both in the case of a thermoplastic matrix and in the case of a thermosetting matrix.

The fibers used for the realization of the pultruded element 30 are preferably glass type E, or carbon fibers for the most stressed portions of the train carriage, and thermoplastic matrix like the Elium by Arkema filled with oxides in order to acquire those characteristics necessary to comply with the European railway standard EN 45545, or thermosetting matrices of the epoxy type such as Sicomin SR 1 155.

The second covering element 70, made of electrically conductive material, is used facing the outside of the train carriage, in an assembled condition of the panel 100, and is preferably made of aluminum or aluminum alloy.

The thickness of the second covering element 70 made of aluminum alloy is preferably between a value of 2.5 mm and a value of 5 mm.

The panels made of aluminum alloy are for example manufactured by extrusion or by folding.

The panel 100 is assembled by gluing the covering elements 30 and 70 described above on opposite faces of the filling, or core, element 50.

The gluing phase using structural adhesives expresses very high safety factors as the involved surface is very large and the adhesive power of the adhesives used is extremely high.

Once the panels 100 have been made, they will be assembled to form the side walls of the carriage, the roof or the floor.

The weight saving obtained is around 30% compared to the construction made of aluminum alloy extruded elements.

The assembly site will be represented by external ribs inside which the pultrudes 30 are inserted so that they remain in position during the gluing phases.

Once the panels 100 have been made, the ribs will be removed and there will be an assembly defined for the roof, side walls and/or floor of a train. In particular, the set of assembled panels 100 constitutes the walls, roof and floor of the train.

This assembly, defining the carriage, must support aerodynamic loads, crash loads, vibration loads, environmental loads, fatigue loads, as better defined by the main regulations listed below:

• EN 15663, Railway applications - Structural requirements of railway vehicle bodies - Part 1 : Locomotives and passenger rolling stock, 2015-3;

• DIN EN 45545-2, Railway applications - Fire protection on railway vehicles - Part 2: Requirements for fire behavior of materials and components; German version EN 455452 - 2013 + A1 : 2015;

• TSI LOC & PAS: 2014, Commission Regulation (EU) No 1302/2014 of 18 November 2014 concerning a technical specification for interoperability relating to the 'rolling stock - locomotives and passenger rolling stock' subsystem of the rail system in the European Union;

• EN 15663: 2017, Railway applications - Vehicle reference masses;

• EN15227: 2008 + A1 : 2010, Railway applications - Crashworthiness requirements for railway vehicle bodies;

• DIN 6701 -3: 2015: Guideline for construction design and verification of bonds on railway vehicles;

• DIN 25201 : 2004: Design guide for railway vehicles and their components -Bolted joins;

• EN ISO 15186-1 : 2003: Acoustics - Measurement of sound insulation in buildings and of building elements using sound intensity - Part 1 : Laboratory measurements (ISO 15186-1 : 2000).

Figure 3 shows an embodiment of an end portion of a train carriage sectioned along a plane parallel to a walking surface. The portions A, B and C are subjected to different loads and stresses in particular during a running condition of the train, for example along a direction indicated with d.

The structural strength values of the structure will obviously depend on the specific dimensioning of the panels.

The value of the thermal resistance of the panel 100 according to the invention is between a value of approximately 1.51 m ² K/W and a value of approximately 2.20 m ² K/W.

In particular, the value of the thermal resistance of the panel 100 is determined by the thickness of the filling element 50.

In the example shown in figure 3, the thermal resistance value must be greater in the portion B, which is the passage area between the side wall C and the front wall A of the carriage. Therefore, the thicknesses of the filling elements 50 will be defined according to the values required by the design.

For example, a filling element 50 having a thickness of 60 mm in the zone A will allow to obtain a thermal resistance value of the panel of the front wall of the carriage equal to about 1 .63 m ² K/W; a filling element 50 having a thickness of 80 mm in the zone B will allow to obtain a thermal resistance value of the panel of the intermediate wall of the carriage equal to about 2.17 m ² K/W; a filling element 50 having a thickness of 55 mm in the zone C will allow to obtain a thermal resistance value of the panel of the side wall of the carriage equal to about 1 .51 m ² K/W.

Advantageously, the panel 100 according to the invention completely meets the requirements required by train manufacturers and by the regulations in terms of thermal insulation, acoustic attenuation, impact resistance, electrical conductivity and fire resistance.

Compared to the constructions, made of alloy, obtained by means of extruded elements composed of two coating skins made of aluminum alloy and a reticular beam that holds them together to form a sort of core, the invention according to the invention - relating to a 100 sandwich panel with a skin of external covering 70 made of aluminum alloy for electrical conductivity and for resistance to impact, a core or filling 50 with high thickness made of expanded thermoplastic material to give the required thermal resistance, to attenuate the noise and to give the necessary moment of inertia to guarantee the rigidity required to support the envelope of the loads to which the train carriage is subjected, and an internal coating skin 30 made of fiberglass or carbon with a thermoplastic or thermosetting matrix to support the loads and contribute to the thermal insulation function - has numerous advantages.

In particular:

• a lower value of heat dispersion: the coefficient of thermal conductivity of aluminum alloys is about 220-290 W/(mxK), the coefficient of thermal conductivity of fiber-reinforced thermoplastic or termosetting matrix composites is about 0.1 -2 W/(mxK), depending on the type of reinforcement used (glass or carbon) which combined with the very low thermal conductivity of the filling expanded material which is about 0.037 W/(mxK) avoids the use of additional thermal insulators, saving space inside the carriage and decreasing the weight;

• the hybrid panel 100 according to the invention, comprising a covering layer 70 made of aluminum alloy, a filling layer 50 made of thermoplastic foam, and a covering layer 30 made of composite material, is lighter than an extruded aluminum alloy panel used in the known art and has a lower cost;

• the hybrid panel 100 according to the invention, comprising a covering layer 70 made of aluminum alloy, a filling layer 50 made of expanded thermoplastic, and a covering layer 30 made of composite material, according to a specific processing of the high-thickness thermoplastic filling layer, it can accommodate power lines and wiring leaving even more interior space inside the carriages;

• the hybrid panel 100 according to the invention, comprising a covering layer 70 made of aluminum alloy, a filling layer 50 made of thermoplastic foam, and a covering layer 30 made of composite material, is 100% recyclable like the panels made of metal alloy;

• the panel 100 according to the invention, comprising a covering layer 70 made of aluminum alloy, a filling layer 50 made of thermoplastic foam, and a covering layer 30 made of composite material, does not require an additional internal finishing operation which is instead applied, for aesthetic reasons, on extruded aluminum alloy panels of a known type;

• the panel 100 according to the invention, comprising a covering layer 70 made of aluminum alloy, a filling layer 50 made of thermoplastic foam, and a covering layer 30 made of composite material, guarantees greater acoustic attenuation than the solution in extruded products of aluminium alloy.

Furthermore, the realization of the panel 100 according to the invention has numerous advantages with respect to the construction of walls and roofs in composite materials with a thermosetting or thermoplastic fiber- reinforced matrix generated by a female or male mold of the prior art, which are made with a single molding process.

In particular:

• a drastic reduction in non-recurring costs is obtained, no need for molds, often heated, of 250 square meters, now in use to make a carriage, no need for autoclaves for the thermal and baric curing of the laminates;

• a better modularity is obtained;

• no need for a conductive skin to discharge to ground the current given by the catenary rupture, as the Al alloy is conductive;

• a greater industrialization of the processes is obtained since the extrusion, or folding, of the external skin is a totally automated process like the pultrusion of the internal skin in composite materials and therefore there are repeatable processes, unlike the laminations processes by means of mold wherein, even a slight misalignment of the fiber with respect to the pre- established lay-up, brings a different response to the envelope of the acting loads;

• greater ease of inspection operations is achieved, in particular through an ultrasonic inspection process, which is an extremely simple and industrialized process for checking composite laminates or folded or extruded sheets. Inspecting a 50-80 cm wide profile, even if continuously 30 meters long, is a simple operation. On the contrary, inspecting a carriage of a known type, for example of 250 square meters, is a much more complex and costly operation.

The present invention has been described for illustrative but not limitative purposes, according to a preferred embodiment thereof, but it is to be understood that variations and/or modifications may be made by those skilled in the art without thereby departing from the relative scope of protection, such as defined by the attached claims.