Title: Reinforced structural insulated panel

TECHNICAL FIELD

This disclosure generally relates to structural insulated panels (SIPs) and in particular to the reinforcement, insulation and jointing of SIPs.

BACKGROUND ART

A SIP is a type of sandwich panel, typically made by sandwiching a core of insulation between two structural skins. The SIPs are fabricated in a factory environment and are customised with apertures for a specific structure. The panels are then transported on-site and assembled together to form a tight, energy-efficient structural and thermal envelope. Such panels are used in the construction industry, as part of a building system, and in the refrigeration industry, in the assembly of cold rooms.

SIPs are currently made with a variety of structural skin materials, including oriented strand board (OSB), Magnesium Oxide (MgO) board and metal.

For the core, the most common materials are PolyURethane (PUR), extruded Polystyrene (XPS) and Expanded Polystyrene (EPS), all petroleum-based derivatives. These core materials have many desirable qualities, such as high thermal insulation values, high strength, low density, widespread availability and an affordable price. However, such materials also have several negative aspects: significant carbon-dioxide production during manufacturing, inherent flammability and limited potential for recycling. There is increasing political and social pressure to replace these petroleum-based products with a more sustainable and environmentally-friendly material. Inter-panel connections on SIPs are being continually improved. US Patent No. 2014250827 discloses a method of connecting in-plane SIPs using connecting splines. US patent No. 20060185305A1 discloses an improved joint structure for adjoining in-plane SIPs using a grooved joint. While such solutions offer numerous advantages, it is now desirable to provide an inter-panel connection that is equally applicable to in-plane and out-of-plane panel configurations.

A strong and durable inter-panel connection is critical for structural integrity, particularly when subject to seismic loading. However, the structural capacity of most types of inter-panel connection is inferior to that of the panel structure. There is a need to improve the overall structural integrity of the SIP so that the strength and durability of the inter-panel connection moves closer to that of the SIP structure.

Accordingly, there is a need for a reinforced SIP that incorporates a sustainably- sourced insulant core and improves inter-panel structural connectivity for both in-plane and out-of-plane panel configurations. The need for such a reinforced SIP exists in both the construction and refrigeration industries. Embodiments of the disclosure are intended to satisfy this need.

It is an objective of the technology disclosed to provide a SIP that overcomes the problems described above. It is an objective of the technology disclosed to provide a reinforced SIP that incorporates a sustainably-sourced insulant core and improves inter-panel structural connectivity for both in-plane and out-of- plane panel configurations.

The information included in this Background section of the specification, including any references cited herein and any description or discussion thereof, is included for technical reference purposes only and is not to be regarded as subject matter by which the scope of the disclosed embodiments is to be bound.

DISCLOSURE OF INVENTION

The technology disclosed herein is a reinforced SIP that incorporates a

sustainably-sourced insulant core and improves the inter-panel structural connectivity for both in-plane and out-of-plane panel configurations.

The improved reinforcement of the SIP as disclosed herein is based on an exoskeleton in the form of a fibre reinforced polymer (FRP) lattice framework. The sustainably-sourced insulant core as disclosed herein includes expanded cork. The improved inter-panel structural connectivity as disclosed herein is based on FRP lacing that is part of the FRP lattice framework.

According to a disclosed embodiment, the reinforced SIP comprises an insulant core, a pair of facesheets and an FRP lattice framework. The lattice framework comprises: (i) a plurality of surface struts embedded into the external surface of each facesheet (ii) a plurality of internal struts connecting the surface struts (iii) a plurality of connectors, and (iv) a plurality of lacing.

According to another disclosed embodiment, the reinforced SIP comprises an insulant core, a pair of facesheets and an FRP lattice framework. The lattice framework comprises: (i) a plurality of surface struts embedded into the external surface of each facesheet (ii) a plurality of internal struts connecting the surface struts (iii) a plurality of connectors, and (iv) a plurality of lacing, a portion of which is connected to an adjoining in-plane reinforced SIP. According to a further disclosed embodiment, the reinforced SIP comprises a core 30, a pair of facesheets 24, 26 and an FRP lattice framework 36. The lattice framework comprises: a plurality of surface struts 41; a plurality of internal struts connecting the facesheets; a plurality of connectors; a plurality of lacing, a portion of which is connected to an adjoining in-plane reinforced SIP. The facesheets 24, 26 and core 30 are triangular. The facesheets 24, 26 incorporate an FRP isogrid structure.

According to another disclosed embodiment, the reinforced SIP incorporates an aperture and comprises a core, a pair of facesheets and an FRP lattice

framework. The lattice framework comprises: (i) a plurality of surface struts embedded into the external surface of each facesheet (ii) a plurality of internal struts connecting the surface struts (iii) a plurality of connectors, and (iv) a plurality of lacing.

According to further disclosed embodiments, the reinforced SIP comprises an insulant core, a pair of facesheets and an FRP lattice framework. The lattice framework comprises: (i) a plurality of surface struts embedded into the external surface of each facesheet (ii) a plurality of internal struts connecting the surface struts (iii) a plurality of connectors, and (iv) a plurality of lacing, a portion of which is connected to an adjoining out-of-plane reinforced SIP.

According to a further disclosed embodiment, the reinforced SIP comprises an insulant core, a pair of facesheets and an FRP lattice framework. The lattice framework comprises: (i) a plurality of surface struts embedded into the external surface of each facesheet (ii) a plurality of internal struts connecting the surface struts (iii) a plurality of connectors, and (iv) a plurality of lacing, a portion of which is connected to adjoining in-plane and out-of-plane reinforced SIPs. According to an additional disclosed embodiment, a method is provided of fabricating a reinforced SIP and connecting to an adjacent reinforced SIP. The method may include sandwiching a core between two facesheets, creating a lattice framework and connecting to an adjacent reinforced SIP. Sandwiching a core between two facesheets may include cutting slabs of expanded cork to size, creating apertures in the expanded cork, cutting the facesheets to size, creating apertures in the facesheets and bonding the core to the facesheets. Creating a lattice framework may include sourcing Carbon Fibre tow, creating connectors, attaching connectors to a thread, plus stitching threads across the core and facesheets. Connecting to an adjacent reinforced SIP may include the on-site linking of lacing and connectors, plus the on-site application and curing of epoxy resin.

Further embodiments of the reinforced SIP are possible. Other features, benefits and advantages of the disclosed embodiments will become apparent from the following description of embodiments, when viewed in accordance with the attached drawings and appended claims.

BRIEF DESCRIPTION OF THE ILLUSTRATIONS

Fig. 1 is a perspective view of a reinforced SIP, showing lacing attached to the facesheets.

Fig. 2 is a cutaway view of Fig. 1. revealing a truss of the lattice framework.

Fig. 3 is an exploded view of the reinforced SIP, showing two series of trusses incorporated into the lattice framework. Fig. 4 is a perspective view of two adjoining reinforced SIPs, showing the inter panel seam.

Fig. 5 is a detail top view of Fig.4, showing a surface spline used to connect the reinforced SIPs.

Fig. 6 is a detail view of Fig.4, showing the lower part of the seam connecting two reinforced SIPs.

Fig. 7 is a detail view of Fig.6, showing a connector and lacing

Fig. 8 is a detail view of the seam on the reverse side of the seam shown in Fig. 6. Fig. 9 is a perspective view of a reinforced SIP, configured as a triangular shape and connected to a similar-shaped reinforced SIP.

Fig. 10 is a perspective view of a reinforced SIP, configured with an aperture.

Fig. 11 is a perspective view of two adjoining reinforced SIPs, configured in a t- junction, showing a seam created at the junction.

Fig. 12 is a detail view of Fig. 11, showing a connector and lacing at the inter panel junction.

Fig. 13 is a perspective view of two adjoining reinforced SIPs, configured in a right-angled corner, with a seam created at the external junction and additional trusses positioned near the junction.

Fig. 14 is a perspective view of two adjoining reinforced SIPs, configured as a roof apex, showing a seam created at the external junction.

Fig. 15 is a perspective view of four adjoining reinforced SIPs.

Fig. 16 is a perspective view of the floor slab shown in Fig.15, detailing the channels cut in the external surface of the upward-facing facesheet

Fig. 17 is a perspective view of the floor slab shown in Fig. 15, detailing the channels cut in the external surface of the downward-facing facesheet

Fig. 18 is a perspective view of a connector.

Fig. 19 is a perspective view of a connector, part-encased in wax. Fig. 20 is a cross-sectional illustration of the reinforced SIP, showing the stitching of threads and the attachment of connectors. It is not drawn to scale in order to give greater clarity to the stitching process.

Fig. 21A is the first part of a flow diagram illustrating a method for fabricating a reinforced SIP and connecting to an adjacent reinforced SIP.

Fig. 21B is the second part of a flow diagram, continuing from Fig. 21A.

Fig. 22 is a flow diagram illustrating a design and construction method.

Fig. 23 is a block diagram of a building constructed with reinforced SIPs.

BEST MODE FOR CARRYING OUT THE INVENTION

The reinforcement of a building structure can be achieved using an exoskeletal framework, whereby the primary structural members are external to the main body of the building and the secondary internal structural members connect with the walls, floors and roof. The exoskeletal framework is very efficient at dissipating applied loads across the structure.

The improved reinforcement of the SIP as disclosed herein is achieved through the addition of an exoskeletal framework. Instead of relying on the local frictional or mechanical resistance of fasteners such as nails or screws to resist axial, bending and shear forces, the addition of a high-strength exoskeletal framework to a SIP absorbs such localised forces and dissipates them across the structure. The exoskeleton incorporates the inter-panel seam into the overall structure of the SIP, thus minimising any imbalance between the strength of the seam and the strength of the facesheets/core combination.

FRP composites are proven materials in the construction and refrigeration industries. High-performance FRP composites made with synthetic fibres such as carbon or glass embedded in polymeric matrices provide the advantages of high stiffness and strength-to-weight ratio. Such material advantages are harnessed in the reinforced SIP as disclosed herein, by adding an exoskeleton in the form of an FRP lattice framework.

Referring first to Figs. 1 to 3, a disclosed embodiment of the reinforced SIP 20 is generally indicated by the numeral 20 and broadly comprises a core 30, a pair of facesheets 24, 26 and an FRP lattice framework 36.

The embodiment of the reinforced SIP 20 shown in Fig.l does not include apertures and is configured solely for connection to adjacent in-plane reinforced SIPs 20. However, as will be discussed below, in another embodiment, the reinforced SIP 20 may be configured to include at least one aperture. In further embodiments, the reinforced SIP 20 may be configured for connections to at least one adjacent out-of-plane reinforced SIP 20.

The core 30 may be cut from a slab of expanded cork, a high-performance solid thermal insulant. The prime function of the core 30 is to reduce heat transfer across the facesheets 24, 26.

The facesheets 24, 26 are bonded to the core 30 and they may be of material that includes OSB, MgO board, metal and cross laminated timber. Each facesheet 24, 26 has four edges 21, comprising a top edge, a bottom edge and two side edges.

The 3-dimensional FRP lattice framework 36 comprises: a plurality of surface struts 41; a plurality of internal struts 42; a plurality of connectors 50, and a plurality of lacing 52. The surface struts 41 may be regularly spaced across the external surfaces 28, 29 of the facesheets 24, 26 where an external surface 28, 29 may be defined as that surface of the facesheet 24, 26 which is not in contact with the core 30. A node 40 is a location where a surface strut 41 may connect with at least one other surface strut 41 and may connect with at least one internal strut 42.

An internal strut 42 may exist between a pair of nodes 40, where each node 40 is on different facesheets 24, 26. The internal struts 42 may be inclined between 0 and 45 degrees from an axis perpendicular to the plane of the facesheets 24, 26. The internal struts 42 may also be arranged to form a plurality of trusses 39 whereby a first series of parallel trusses 39 may be embedded in the reinforced SIP 20 in one direction. A second series of parallel trusses 39 may be embedded in the reinforced SIP 20 at an angle to the first series. A third series of parallel trusses 39 may be embedded in the reinforced SIP 20 at an angle to the first series and at a different angle to the second series.

According to another disclosed embodiment which is illustrated in Figs. 4 to 8, the reinforced SIP 20 comprises a core 30, a pair of facesheets 24, 26 and an FRP lattice framework 36. The lattice framework 36 comprises: (i) a plurality of surface struts 41 embedded into the external surfaces 28, 29 of the facesheets 24, 26 (ii) a plurality of internal struts 42 connecting the surface struts 41 (iii) a plurality of connectors 50, and (iv) a plurality of lacing 52, a portion of which is connected to an adjoining in-plane reinforced SIP 20. Two reinforced SIPs 20 may be positioned adjacent to each other where they are designated as wall panels and are positioned to form a larger wall. Typically, a permanent joint is created at the two edges 21 where the reinforced SIPs 20 meet, using surface splines 68 as illustrated in Fig. 5, or using another type of joint. No claim is made in respect of the spline 68. A connector 50 may be a small FRP ring that is attached to a surface strut 41 at a node 40. A series of connectors 50 may be placed near to the joint line of two adjoining reinforced SIPs 20. A lacing 52 may be a length of flexible FRP that is initially secured to a facesheet 24, 26 of a first reinforced SIP 20 and then used on-site to link a series of connectors 50 on the first reinforced SIP 20 to a series of connectors 50 on an adjacent second reinforced SIP 20. Epoxy resin may be subsequently applied to the lacing 52 and connectors 50; curing of the epoxy results in the creation of an inter-panel seam 53. Where the adjacent reinforced SIPs 20 are in the same plane, one seam 53 may be located on the external surface 28 and another seam 53 may be located on the external surface 29, as illustrated in Fig. 8.

For illustrative purposes only, the disclosed embodiment as illustrated in Fig. 4 is described in reference to forming a reinforced SIP 20 for use as part of a wall in a building. However, while a wall with a flat plane is shown, the disclosed embodiment is equally applicable to a reinforced SIP 20 having curvature along one dimension. Furthermore, while a wall is shown, the disclosed embodiment is equally applicable to floors and roofs. Furthermore, while a wall of rectangular dimensions is shown, the disclosed embodiment is equally applicable to a reinforced SIP 20 that has three or more sides.

According to another disclosed embodiment which is illustrated in Fig. 9, the reinforced SIP 20 comprises a core 30, a pair of facesheets 24, 26 and an FRP lattice framework 36. The facesheets 24, 26 and core 30 are triangular. The lattice framework 36 comprises: a plurality of surface struts 41; a plurality of internal struts 42 connecting the facesheets 24, 26; a plurality of connectors 50; and, a plurality of lacing 52, a portion of which is connected to an adjoining in- plane reinforced SIP 20. The facesheets 24, 26, comprising an FRP layer and an FRP isogrid structure, may be integral with the FRP surface struts 41. The isogrid structure comprises upstanding FRP ribs that are arranged as a series of substantially equilateral triangles.

The lattice framework 36 may be optimised by considering the stresses experienced by the facesheets 24, 26 when an aperture 60 is introduced into the reinforced SIP 20 or when the facesheets 24, 26 are subject to asymmetric loading.

The effect of an aperture 60 within the reinforced SIP 20 may be observed in the disclosed embodiment which is illustrated in Fig. 10. In this embodiment, the reinforced SIP 20 features an aperture 60 and comprises a core 30, a pair of facesheets 24, 26, and an FRP lattice framework 36 with trusses 39 positioned to provide structural support around the aperture 60. The structural stability of the aperture 60 may be enhanced by increasing the density of trusses 39 around the aperture 60. By placing a sufficient density of trusses 39 around each aperture 60, the perimeter of the aperture 60 may be transformed from an area of weakness to an area of structural strength. This permits any required timber framing of the aperture 60 to be minimised. The result is a more efficient structural design and greater design freedom to position and size the apertures

60.

Examples of asymmetric loading on the reinforced SIP 20 are observed in further disclosed embodiments, illustrated in Figs. 11 to 14, wherein the reinforced SIP 20 comprises a core 30, a pair of facesheets 24, 26, and an FRP lattice framework 36. The lattice framework 36 includes connectors 50 configured to create a surface-embedded seam 53 with an adjacent out-of-plane reinforced SIP 20. Out-of-plane configurations may include a t-junction, a right-angled corner junction and an obtuse-angled corner junction.

A t-junction configuration may be observed in the disclosed embodiment which is illustrated in Fig. 11. In this embodiment, the facesheet 24 of the reinforced SIP 20 is abutted by two edges 21 of another reinforced SIP 20. Two seams 53 are created on the facesheet 24 that is in contact with the two edges 21 of the abutting reinforced SIP 20. The illustration in Fig. 12 shows the connection detail of a seam 53 at an internal corner, specifically the attachment of a lacing 52 to a connector 50 that is secured to the surface strut 41. The raised stress levels in the vicinity of the two seams 53 may be relieved by increasing the density of trusses 39 in the stress-loaded areas of both reinforced SIPs 20.

A right-angled corner junction configuration may be observed in the disclosed embodiment which is illustrated in Fig. 13. In this embodiment, two edges 21 of the reinforced SIP 20 are connected to two edges 21 of an adjoining reinforced SIP 20 and the reinforced SIPs 20 are positioned at right angles to each other. Two seams 53 are created, one at the internal corner and another at the external corner. The raised stress levels at the corner seams 53 may be relieved by increasing the density of trusses 39 of both reinforced SIPs 20 in the region of the corner seams 53.

An obtuse-angled junction configuration may be observed in the disclosed embodiment which is illustrated in Fig. 14 In this embodiment, two edges 21 of the reinforced SIP 20 are connected to two edges 21 on an adjoining reinforced SIP 20 and the reinforced SIPs 20 are positioned at an obtuse angle to each other. Two seams 53 are created, one at the internal corner and another at the apex. The raised stress levels at the angled seams 53 may be relieved by increasing the density of trusses 39 of both reinforced SIPs 20 in the region of the junction seams 53.

The reinforced SIP 20 may be connected simultaneously to a plurality of adjacent reinforced SIPs 20, both in-plane and out-of-plane, as observed in the disclosed embodiment which is illustrated in Fig. 15. In this embodiment, the reinforced SIP 20 incorporates an aperture 60, connects with an adjacent in-plane reinforced SIP 20 and also connects with two adjacent out-of-plane reinforced SIPs 20. Seams 53 are created at each junction; trusses 39 are positioned as required to relieve the stresses occuring around the apertures 60 and at the seams 53. Where a plurality of reinforced SIPs 20 are connected by seams 53, the resulting network of connected lattice frameworks 36 provides an overall structural strength that is greater than the sum of its parts.

The reinforced SIP 20 may be connected to other reinforced SIPs 20 in various other configurations in other embodiments not detailed herein. The following information is applicable to all disclosed embodiments.

In order to enhance the adhesion of the lattice framework 36 to the external surface 28 of the reinforced SIP 20, channels 66 may be cut into the external surface 28 as illustrated in Fig. 16. The pattern of channels 66 cut into the external surface 28 may vary according to the design of the lattice framework 36. As illustrated in Fig. 7, a short section of the channel 66 may be reserved for the placement of the connector 50 in order to facilitate the subsequent attachment of the lacing 52 within the channels 66. In order to enhance the adhesion of the lattice framework 36 to the external surface 29 of the reinforced SIP 20, channels 67 may be cut into the external surface 29, as illustrated in Fig. 17. The pattern of channels 67 cut into the external surface 29 may vary according to the design of the lattice framework 36.

The channels 66, 67 may have a depth of between about 0.05mm and about 10mm. For example, the depth may be about 0.05mm to about 1mm, or about 0.05mm to about 2mm, or about 0.1mm to about 2mm, or about 0.3mm to about 2mm, or about 1mm to about 10mm. The channels 66, 67 may have a width of between about 0.05mm and about 10mm. For example, the width may be about 0.05mm to about 1mm, or about 0.05mm to about 2mm, or about 0.1mm to about 2mm, or about 0.3mm to about 2mm, or about 1mm to about 10mm.

The surface struts 41, connectors 50 and lacing 52 may be bonded into the channels 66, 67 by the addition of a bonding agent that includes epoxy resin. By surface-embedding these elements of the lattice framework 36 into the channels 66, 67, the reinforced SIP 20 increases its capacity to resist axial loads, bending moments and shear forces.

The ability to assign the density and orientation of trusses according to the forces acting on the reinforced SIP 20 results in a very efficient structural design. This optimisation of the structural design minimises the requirement for timber blocking or bracing at junctions and apertures 60. One advantage is the reduction of cold bridging, which is the unwanted transfer of heat across the facesheets 24, 26. Another advantage of reduced timber blocking and bracing is that the strength-to-weight ratio is improved, permitting longer spans or greater live loads to be applied to the timber-reduced structure. The lattice framework 36 of the reinforced SIP 20 may be designed so that its surface struts 41 largely align with the surface struts 41 of lattice frameworks 36 of adjoining reinforced SIPs 20. The result is the formation of a largely coherent lattice framework 36 across a connected assembly of reinforced SIPs 20. The alignment of surface struts 41 in this way promotes an efficient transfer of stresses across the adjoining reinforced SIPs 20. With the lattice frameworks 36 of adjoining reinforced SIPs 20 thus aligned, it is a simple process to then adjust the length and width dimensions of any reinforced SIPs 20 so that the channels 66, 67 are ideally positioned and do not coincide with the edges 21 of the reinforced SIPs 20. The lattice framework 36 may also be designed so that the internal struts 42 of a reinforced SIP 20 do not obstruct the on-site installation of splines 68.

Cork is a natural product, harvested as the bark of cork oak trees that grow in Southern Europe and North Africa. The harvesting takes place every 9 years without detriment to the tree and cork is therefore a highly sustainable crop. Low-grade or waste cork is processed, without additives, in a high-temperature steam autoclave to produce expanded cork, also known as black cork or corkboard.

Expanded cork is a high-performance thermal insulant and, as a sustainably- sourced material, is highly suitable as an environmentally-friendly core 30. In addition, it has low flammability and has good recycling properties. In all respects, expanded cork is a great improvement on the petrochemical derivatives currently used as the core 30. Although expanded cork has relatively low shear resistance, the installation of the trusses 39 into the reinforced SIP 20 provides a significant level of shear resistance. Expanded cork has a thermal conductivity in the range of 0.035 - 0.043 Watts per meter-Kelvin (W/m-K), which is of the same magnitude as the thermal conductivity values of 0.023 W/m-K for PUR, 0.030 W/m-K. for XPS and 0.036 W/m-K. for EPS. The lattice framework 36 may be fabricated from Carbon FRP; the thermal conductivity of Carbon FRP is in the range of 0.15 to 5.0 W/m-K which, in the extreme, is 100 times that of expanded cork and the petroleum- based products. However, a typical cross-section of the reinforced SIP 20 may have approximately one square millimetre of lattice framework 36 for every 2000 square millimetres of the expanded cork core 30. This l-to-2000 ratio suggests that the higher thermal conductivity of Carbon FRP may increase the thermal conductivity of the combined Carbon FRP/expanded cork core 30 by about 5% when compared to a core 30 solely comprised of expanded cork.

The volume of timber blocking and bracing may be reduced as a result of the additional strength provided by the lattice framework 36. The redundant timber is replaced by expanded cork, a factor which will reduce the overall thermal conductivity of the reinforced SIP 20. Taking into account this reduction in timber and the introduction of the Carbon FRP, the net increase in thermal conductivity of the combined Carbon FRP/expanded cork core 30 is likely to be less than 5%. This is an acceptable compromise to achieve the replacement of the petroleum-based products.

Fabrication of the lattice framework 36 may use tow, which is a bundle of high- tensile strength fibre such as Kevlar or Carbon. Tow can be spooled into lengths of hundreds of metres and it can have a cross-section as small as 1.5mm by 0.15mm. Fabrication of the lattice framework 36 may involve three main processes. The first two processes take place in a factory environment and are (1) the fabrication of a connector 50, and (2) the fabrication of the surface struts 41 and the internal struts 42. The third process takes place on-site, where the reinforced SIP 20 will be installed, and comprises (3) the fabrication of a seam 53.

The fabrication of a connector 50 is now described. A connector 50 may be a single ring of tow, created by slicing thin sections from a tube of tow. A connector 50 may have a diameter of between about 2mm to about 100mm. For example, the diameter may be about 2mm to about 50mm, or about 2mm to about 30mm, or about 2mm to about 10mm, or about 5mm to about 100mm. Each ring of tow is oval-shaped, as illustrated in Fig. 18. The oval-shaped ring is then part-dipped into a molten wax and the resultant wax coating 38 is allowed to cool and solidify. Waxes are a diverse class of organic compounds that are lipophilic, malleable solids near ambient temperatures; accordingly, the most appropriate compound may be used for this process. As illustrated in Fig. 19, the resulting connector 50 is a part-waxed oval-shaped ring. The unwaxed part of the connector 50 is the primary opening 54, which may be used to attach the connector 50 to a surface strut 41. The part of the connector 50 with a wax coating 38 is the secondary opening 56. The wax coating 38 is a temporary protection to the secondary opening 56 to ensure it is not filled with resin when the resin is applied in the creation of the surface struts 41. The secondary opening 56 may be used later, after removal of the wax coating 38. It will then be linked with lacing 52 to create a seam 53.

The fabrication of the surface struts 41 and the internal struts 42 is now described. Referring to Fig.20, an industrial stitching technique is now described that derives from FRP stitching processes used extensively in the aerospace industry. The technique described is one of several techniques available that uses two threads and there are other techniques available that use a single thread. The stitching technique described is therefore one of several that can be used in the fabrication of the disclosed embodiments.

The surface struts 41 and internal struts 42 may be created by adding epoxy resin to tow threads 70, 72, followed by a period of curing. The first thread 70 may be spooled into a first channel 66 that runs across the external surface 28 of the first facesheet 24. The second thread 72 may be spooled through an epoxy bath (not shown) into a second channel 67 that runs across the external surface 29 of the second facesheet 26 and may be aligned with the first channel 66.

The placement of the threads 70, 72 in the channels 66, 67 has the following benefits: the bonding surface is maximised between the threads 70, 72 and the facesheets 24, 26; the threads 70, 72 are less susceptible to impact damage during subsequent transport and installation of the fabricated reinforced SIPs 20, and; the external surfaces 28, 29 of the facesheets 24, 26 are kept clear for any subsequent construction processes.

The stitching of the first and second threads 70, 72 to create the lattice framework 36 may be performed using stitching equipment (not shown) that includes, without limitation, an automated toolhead operated by a programmed computer. A hooked needle 75 may be pushed through a hole 46 that has been drilled through the facesheets 24, 26 and the core 30. A loop 48 of the second thread 72 may then be caught by the hooked needle 75 and pulled back through the hole 46. The first thread 70 may then be passed through the loop 48.

Where a connector 50 is to be placed at a node 40, the stitching process may be adjusted according to whether the node 40 is at the first facesheet 24 or at the second facesheet 26. Where the node 40 is at the first facesheet 24, the hooked needle 75 may pass through the primary opening 54 of the connector 50, and then may pierce the facesheets 24, 26 and the core 30. After hooking a loop 48 of the second thread 72, the needle 75 may retract from the facesheets 24, 26, the core 30 and the connector 50. The stitching equipment may feed the first thread 70 through the loop 48. The first and second threads 70, 72 may then be tightened to lock the stitch with the connector 50 attached.

Where the node 40 is at the second facesheet 26, the hooked needle 75 may first pierce the facesheets 24, 26 and the core 30 and may then pass through the primary opening 54 of the connector 50. After hooking a loop 48 of the second thread 72, the needle 75 may retract from the connector 50, leaving the connector 50 attached to the second thread 72 at the node 40.

The first and second threads 70, 72 are locked by tensioning; the stitching process may now be repeated. The process may continue until the stitching of all series of trusses is complete for the entire reinforced SIP 20.

When the stitching of the reinforced SIP 20 is complete, the reinforced SIP 20 may be positioned in the horizontal plane. Epoxy resin may then be added to the uppermost channel 66 of the first facesheet 24 to impregnate the threads 70 and to act as the bonding agent between the threads 70 and the channels 66. After partial curing of the impregnated threads 70, the reinforced SIP 20 may be turned through 180 degrees so that the second facesheet 26 is uppermost.

Epoxy resin may now be added to the channels 67 of the second facesheet 26 to act as the bonding agent between the threads 72 and the channels 67. Bonding between the threads 70,72 and the facesheets 24, 26 contributes to the structural strength of the reinforced SIP 20. In particular, the confinement of the threads 70, 72 within the epoxy-filled channels 66, 67 improves the compressive strength of the surface struts 41, once cured.

The expanded cork core 30 may be slightly compressed during the installation of the lattice framework 36. The subsequent release or partial release of the external compressive force prior to or during curing may apply tension to the lattice framework 36, helping the lattice framework 36 to maintain contact with the channels 66, 67. Tensioning of the tow prior to or during curing may also assist in achieving the maximum possible cured strength. Expanded cork exhibits a small compressive creep effect, low permanent deformation and a

compressive strength that is capable of resisting the applied tensioning forces. These properties are advantageous to the process of applying and removing an external compressive force during installation of the lattice framework 36.

After the curing of the surface struts 41 and the internal struts 42, one end of each lacing 52 is secured to the facesheets 24, 26. The application of heat melts the wax coating 38 of the attached connectors 50, exposing the secondary openings 56. The reinforced SIP 20 may then be transported to site and installed in the usual way.

The fabrication of a seam 53 is now described. The lacing 52 may be created from tow. The lacing 52 may be threaded through the secondary openings 56 of the connectors 50 on both the reinforced SIP 20 and any adjoining reinforced SIP 20. One or more lacing 52 can be used to create a seam 53. A connector 50 may be secured to several lacing 52. The lacing 52 and the connectors 50 sit within channels 66, 67 on both of the adjoining reinforced SIPs 20. Epoxy is added to the channels 66, 67 and the epoxy is then cured. The result of combining epoxy with the lacing 52 and the connectors 50 is a high-strength seam 53.

Other types of lacing 52 and connectors 50 may also be used to create a seam 53. An alternative method of creating a seam 53 may be to create a lacing 52 that attaches to a connector 50 without passing through an opening in the connector 50. An alternative lacing 52 may be one that is created as a solid object and attached to connectors 50. An alternative lacing 52 may be one that is integral with one or more connectors 50 and a link is created by joining said connectors 50. The linking of lacing 52 to connector 50, or of lacing 52 to lacing 52, or of connector 50 to connector 50, or of lacing 52 to the surface struts 41 or internal struts 42, or of connector 50 to the surface struts 41 or internal struts 42, may include a method of applying epoxy, snapping onto or clipping into or screwing into each other, without limitation as to the method of attachment. An alternative connector 50 may be one that is integral to a surface strut 41 or an internal strut 42. An alternative connector 50 may be one that is integral to the lacing 52 or one that links to another connector 50 without an intermediate lacing 52. The lacing 52 and connectors 50 suggested above are just a few examples of the different methods of creating a seam 53 and other variations will occur to those of skill in the art.

The combination of the seam 53 with surface struts 41 and internal struts 42 produces an exoskeleton. The resulting network of exoskeletons provides a strength and durability to the building structure that is not attainable by the currently-available inter-panel connections. Another advantage of adding an exoskeleton to the reinforced SIP 20 is that it helps to limit delamination of the facesheets 24, 26 from the core 30.

Delamination is a typical mode of failure for sandwich-type panels under excessive axial load, occuring first by a facesheet 24, 26 bending, and then detaching from its bond with the core 30. With an exoskeleton in place, the facesheets 24, 26 are confined by the surface struts 41, which are themselves held in place by both the internal struts 42 and the seams 53. The tensile strength of the FRP internal strut 42 is now an additional and significant factor in the prevention of delamination.

Catastrophic failure of the inter-panel joint often precedes the collapse of a building during an earthquake. In order to give the occupants time to evacuate the building, the joint failure needs to be delayed. This can be achieved by strengthening the joint and incorporating a sufficient level of deformation ductility into the joint. The addition of the exoskeleton to the reinforced SIP 20 significantly increases the strength of the inter-panel connection. Although FRP is not typically associated with ductile failure, its use in the fabrication of a lattice framework 36 is able to transform the failure mode. A progressive failure is the key to the dissipation of seismic energy prior to a joint failure mode eventually becoming critical. Accordingly, the lattice components are allowed to fail progressively, typically by local shear failure at the nodes 40 of the FRP lattice framework 36. This failure sequence applies to both in-plane and out-of-plane panel configurations, resulting in a structure that is highly resilient when subject to seismic and other applied forces.

Referring now to Fig.21A, a method of fabricating a reinforced SIP 20 and connecting to an adjacent reinforced SIP 20 begins at step 100 by procuring the blocks of expanded cork. At step 102, the core 30 may be created by cutting the expanded cork to size and creating apertures 60 as required.

Separately, the facesheets 24, 26 are prepared, by following steps 104 - 108.

Step 104 is the procurement of the facesheets 24, 26. The next step 106 is where the facesheets 24, 26 are cut to size and any required apertures 60 are created. At step 108, the bonding agent may be applied to the side of the facesheets 24, 26 to be bonded to the core 30.

At step 110, the core 30 may be bonded between the facesheets 24, 26. The sandwiched core 30 and facesheets 24, 26 may be placed in a heat press (not shown) for the bonding process.

At steps 112 and 114, the facesheets 24, 26 are cut and drilled using joinery equipment (not shown) that includes, without limitation, an automated toolhead operated by a programmed computer. At step 112, the joinery equipment may cut channels 66, 67, in a pattern dictated by the design of the lattice framework 36, into the external surfaces 28, 29 of the facesheets 24, 26. The channels 66,

67 may be sized to accommodate the surface struts 41, the lacing 52 and the connectors 50. At step 114, the joinery equipment may drill a plurality of holes 46, at the desired angle from vertical, through the facesheets 24, 26 and the core 30 at the nodes 40.

Separately, at Step 118, the tow and the epoxy resin may be procured. At step 120, the connectors 50 may be created from rings of tow. At Step 122, the lattice framework 36 is stitched, incorporating connectors 50 as required. Referring now to Fig. 21B, continuing the method shown in Fig. 21A, step 124 is where the reinforced SIP 20 may be positioned in the horizontal plane and epoxy resin is added to the channels 66 in the uppermost facesheet 24. The

impregnated threads 70 may then be part-cured. At step 126, the reinforced SIP 20 may be rotated through 180 degrees so that the previous downward-facing facesheet 26 is now uppermost. Epoxy resin may then be added to the channels 67 in facesheet 26. At step 128, the epoxy is cured, lacing 52 is attached to the facesheets 24, 26 and the application of heat melts the wax coating 38.

At step 130, the reinforced SIP 20 is transported to site and secured adjacent to another reinforced SIP 20. At step 132, the lacing 52 is linked to the secondary openings 56 of the connectors 50 on both reinforced SIPs 20. At step 134, epoxy resin may be added to the channels 66, 67 containing the lacing 52 and connectors 50. At step 136, the epoxy is cured.

INDUSTRIAL APPLICABILITY

Embodiments of the disclosure may find use in a variety of potential

applications, particularly in the construction and refrigeration industries. Thus, referring now to Figs. 22 and 23, embodiments of the disclosure may be used in the context of a building design and construction method 220 as shown in Fig. 22 and a building 136 as shown in Fig. 23. Construction applications of the disclosed embodiments may include, for example, without limitation, reinforced SIPs 20 for use in wall systems, floor systems and roof systems or a combination of such systems, to name a few.

During design of the building 136, exemplary method 220 may include a consideration of the stresses (222) acting at the junctions of an adjoining reinforced SIP and at each aperture, positioning of trusses (224) to accommodate the local forces, dimensioning of facesheets and the core (226) and the assignment of connectors to nodes (228). During off-site fabrication, sandwiching of the core between facesheets (230) takes place, followed by fabricating the lattice framework (232). Following Transport and Installation on site (234), Seam Creation (236) takes place.

The preferred method 220 of the disclosed embodiment is well suited for forming reinforced SIPs 20 that form part of a building system for residential, commercial, civic and other type of buildings. The construction method described and material selection used in the fabrication of the reinforced SIP 20 renders the reinforced SIP 20 suitable to be utilised in multi-level building construction, particularly in earthquake-prone locations.

As shown in Fig. 23, the building 136 produced by exemplary method 220 may include a plurality of structures 138, systems 148 and fixtures 150. Examples of high-level structures 138 include one or more of a reinforced SIP 140, substructure 144 and other structures 146. Any number of other structures 138 may be included. Although a construction example is shown, the principles of the disclosed embodiment may be applied to other industries, such as the refrigeration industry.

Although the embodiments of this enclosure have been described with respect to certain exemplary embodiments, it is to be understood that the specific embodiments are for purposes of illustration and not limitation, as other variations will occur to those of skill in the art.