CA2855378A1

CA2855378A1 - Precursor laminate and method for forming a laminate

Info

Publication number: CA2855378A1
Application number: CA2855378A
Authority: CA
Inventors: Winston Mackelvie
Original assignee: Rainvestment Management Sarl
Current assignee: Rainvestment Management Sarl
Priority date: 2014-07-02
Filing date: 2014-07-02
Publication date: 2016-01-02

Description

PRECURSOR LAMINATE AND METHOD FOR FORMING A LAMINATE
FIELD OF THE INVENTION
The present disclosure relates to laminates and composites and methods of making same.
BACKGROUND OF THE INVENTION
Laminates and composites are relatively light, stiff and strong compared to the materials that make up the constituent layers or lamina.
The term "laminate" generally refers to relatively thin layers of material bonded together under heat and pressure to create sheets of laminate from which articles can be made. Plywood is common example comprising layers of thin wood bonded together. The result is very strong compared to the thin wood constituent layers.
Composites are generally thicker, with skins and cores of different materials.
Skins are generally a thin, stiff material bonded over a thicker porous core material.
For example, yachts, aircraft, bridges, and racing cars use composites. Composites can be flat such as for floors, or molded into curved shapes such as hulls, wings and chassis.
Construction of current laminates and composites generally requires one or more adhesive systems, which are expensive, require considerable time and skill to use, may comprise toxic chemicals, and may need sophisticated equipment that requires careful cleaning.
SUMMARY OF THE INVENTION
A precursor laminate is provided, being formed from a first layer of ductile material with a face textured with a plurality of barbs, and a second layer of a heat-fusible material disposed on the textured face of the ductile material. When the heat-fusible material is heated to at least its melting point, the heat-fusible material at least partially melts so as to wet and surround a multiple barbs so that when the heat-fusible material is subsequently cooled and solidified, the ductile material and the heat-fusible material are locked together to form a laminate.
The first layer is preferably a sheet of ductile material, which is preferably made from steel. The heat-fusible material is preferably a thermoplastic material, which may be in sheet foim, and the precursor laminate may be formed by pressing the thermoplastic material onto the textured face of the sheet of ductile material so that multiple barbs pierce the thermoplastic material.
Both the upper and lower faces of the sheet of ductile material may be textured with multiple barbs, and the second layer of heat-fusible material may be disposed on, or affixed to, the upper face of the sheet of ductile material, with a third layer consisting of heat-fusible material disposed on the lower face, so that when the heat-fusible material in both the second and third layers is heated to at least the melting point, the heat-fusible material at least partially melts so as to wet and surround multiple barbs on each of the faces so that when the heat-fusible material is subsequently cooled and solidified, the ductile material and the heat-fusible material are locked together to form a laminate.
The heat-fusible material may be (1) fibrous, (2) one or more layers of film, (3) a particulate, or (4) pre-preg.
Preferably, the first layer of the precursor laminate is substantially flat.
Some or all of the barbs may be clinched.
The invention also provides a three-layer precursor laminate with first and second layers, each being a substantially flat sheet of a ductile material with a face textured with multiple barbs. The precursor laminate also has a third layer of heat-fusible material positioned between the first and second layers in engagement with the textured face of each of the first and second layers so that the heat-fusible material surrounds multiple barbs on both the first and second layers. Then, when the heat-fusible material is heated to at least its melting point, the heat-fusible material at least partially melts so that it wets and surrounds multiple barbs. Then, when the heat-fusible material is subsequently cooled and solidified, the ductile material and the heat-fusible material are locked together to form a laminate.
The invention also provides composite panels with at least one panel component made from one of the above-described precursor laminates.
The invention also provides a method of forming a laminate. First, a precursor laminate comprising a first layer comprising a sheet of a ductile material having a face textured with a

2 plurality of barbs, and a second layer comprising a heat-fusible material disposed on the textured face of the sheet of ductile material, is provided. Then the heat-fusible material is heated to at least its melting point to cause the heat-fusible material to at least partially melt so as to wet and surround a plurality of the barbs. Then, the heat-fusible material is cooled so that it solidifies and the ductile material and the heat-fusible material are locked together to form the laminate.
The invention also provides a method of forming a laminate from a sheet of a ductile material having a face textured with a plurality of barbs. A heat-fusible material is applied to the textured face of the sheet of a ductile material. Then the heat-fusible material is heated to at least its melting point to cause the heat-fusible material to at least partially melt so as to wet and surround a plurality of the barbs. Then, the heat-fusible material is cooled so that it solidifies and the ductile material and the heat-fusible material are locked together to form the laminate. The heat-fusible material may be in the form of a sheet, and the heat-fusible material may be applied to the textured face of the sheet of ductile material by pressing the sheet of heat-fusible material against the textured face of the sheet of ductile material so that multiple barbs enter, or pierce, the sheet of heat-fusible material.
BRIEF DESCRIPTION OF THE DRAWINGS
Figure 1 shows a cross section of a portion of a sheet of rigid material having an illustrative single hooked barb, the result of a cutting tooth plowing a short, shallow, surface groove.
Figure la shows a typical row of such barbs on a first material.
Figure 2 shows a cross section of a first material with pointed, piercing barbs mechanically engaging a fabric to make an elemental precursor laminate.
Figure 2a shows a first material with barbs on both faces, the upper face having retentive, hooked or curved barbs engaging a fabric second material, the lower face having pointed, piercing barbs engaging multiple layers of plastic film.
Figure 3 shows an exploded view of one embodiment of a precursor laminate where outer upper and lower layers (skins) of second material (fabric) sandwich a central layer of first

3 material barbed on both upper and lower faces.
Figure 3a shows an exploded view of a second embodiment of a precursor laminate where the outer skin layers are a first material sandwiching a core layer of thermoplastic fabric second material.
Figure 4 shows the layers of Figure 3 mechanically attached together to form a precursor laminate.
Figure 4a shows the layers of Figure 3a mechanically attached together to form a precursor laminate.
Figure 5 shows a truss shaped (flat-bottomed V) core component for a composite panel, formed from the precursor laminate shown in Figure 4.
Figure 6 shows an end view of a round-corrugate truss shape of precursor laminate with both face surfaces textured and having the second material engaging both barbed faces.
Figure 7 shows an end view of a square corrugate precursor laminate with both face surfaces textured and having the second material engaging both barbed faces.
Figure 8 shows an end view of a Vee corrugate precursor laminate with both face surfaces textured and having the second material engaging both barbed faces.
Figure 9 is a skin component for the same composite panel made of precursor laminate with the barbed, upper face engaging the flexible second material.
Figure 10 shows a loose assembly of the composite panel components where several truss members of Figure 5 lie side-by-side on the lower skin of Figure 9. The barb texturing has been omitted for clarity, but all internal contacting surfaces are barbed.
Figure 11 shows two outer skin components sandwiching core truss components and how a slot and a tongue joint are formed from the flange ends.
Figure 12 shows three composite sandwich panels joined using the tongue and slot shown in Figure 11.
Figure 13 shows how the panel can be made from curved skins and reshaped core trusses.
This can begin as an assembled precursor flat composite panel which is then curved, reshaping

4 all the components together.
Figure 14 shows a cross section of precursor laminate where the first sheet material has barbs on both faces and a fabric (or layers of fabric) are engaging the upper barbs that have been clinched (bent over), and a thinner textile layer plus a woolly spacer material are both shown engaging the barbs of the lower face.
Figure 15 shows a portion of a permanent laminate of the instant construction method where two outer layers of first material are joined together by the hardened, solid second material between which has been melted so as to flow about their barbs, and then allowed to cool to a hard solid thereby locking the barbs together.
Figure 16 shows two precursor laminate layers that can be joined by simply heating to the melting point of the second material.
Figure 17 shows a cross section of a composite cylinder where an inner cylinder of precursor laminate is wrapped with and outer skin of first material.
Figure 18 shows a side view of two layer precursor laminate brackets bent, assembled and heated to join the barbs together making a composite bracket.
Figure 19 shows how the composite cylinder of Figure 17 has a layer of first material spirally wound on a mandrel with barbs facing outwards, and spirally wrapped with second material.
Figure 20 shows the same embodiment with the outer skin of first material having barbs facing inwards wrapped over the core second material.
Figure 21 shows multiple layers of precursor laminate with single- and double-barbed layers of first material, and including core layers of second material and where screening serves to hold the laminates apart to increase overall thickness of the finished composite panel.
DETAILED DESCRIPTION OF THE INVENTION
A precursor laminate comprises first and second materials where the first material is preferably in sheet form and has been processed to have a texture comprising raised retention elements, which may be referred to as "barbs". The first material is preferably a ductile material in rigid sheet form, which may be sheet metal or plastic, for example, that can be

5 subjected to a tooling process that textures one or both surfaces ("faces") of the sheet with barbs. The first material may be steel, aluminum, stainless steel, copper, polyethylene or nylon, for example. Steel is particularly preferred as the first material.
The barbs of the first material may have various shapes, densities and dimensions. For example, the barb tips may be spike-like for piercing, or hook-like for retention. Both barbs types can be clinched, or upset or bent over, to create a head to increase retentive properties.
This can be done during the texturizing process or afterwards during the laminating process.
The second material is a heat-fusible solid material such as fabric, powder or a solid in liquid suspension that is conformable to the barbs so that it can be placed on a face of the first material having barbs so that it surrounds a plurality of the barbs. It is able to mechanically attach to, or engage, envelope, be entrapped by, coat, wet, adhere, cling to, be hooked by, or lock onto, the barbs such that the first and second materials behave as a single layer and will not readily separate under handling. For example, the second material may be a sheet of thermoplastic material that is pressed onto a sheet of the textured surface of the first material so that the barbs pierce the thermoplastic material to foim a mechanical attachment.
The second material must be heat-fusible so that it can be heated to at least partly melt the material and wet the barbs, and then be cooled to cause the material to solidify so that it is transformed into a continuous, rigid solid. Upon this transformation, the hard solid second material is locked in place by the barbs, bonded to the first material, to form a laminate. In this way a precursor laminate of two outer first materials and a centre layer of second material will become a permanent laminate when the second material transforms into a hard solid bonded to the barbs of the two sheets.
Examples of second materials include, but are not limited to, thermoplastics, thermoset pre-pregs of glass or carbon fibre, mixtures and slurries such as cement for dipping, spraying, brushing, spreading, and dry powder such as electrostatic spray epoxy. Each has advantages with respect to cost, process speed, durability and the like.
Combinations of such materials and folms are also contemplated. For example, sheet aluminum and sheet nylon as outer skin layers can have low melt temperature polyethylene as a core layer.

6 After exposure to appropriate heating and cooling conditions they too will coalesce/harden locking the barbed sheets together. For example, powdered glass can be applied to the facing barbs of two first material pieces (using well known enamelling techniques) to create precursor laminates. Assembled and heated, the glass fuses to itself and to the barbs to make a one-piece laminate of steel and glass.
One example of a preferred first material (sheet textured with barbs) is available from Nucap Industries of Toronto, Canada under the name NRX. The material may have one or both faces textured throughout, or in select locations over one or both faces. Such material is also described in International Patent Application Number PCT/CA2013/000500 (publication number WO/2013/177667).
By barb is meant a raised tongue or hook of material displaced from a groove to which it remains firmly attached. In making NRX, multiple rows of short, shallow grooves are plowed bi-directionally into the surface of sheet material by toothed blades.
By conforming is meant an aggregate of fibres, films or particles that can readily contact, engage and/or coat the barbs by pressing, impaling, brushing, blowing, rubbing pouring, spraying, electrostatic application, and the like. Non-rigid heat-fusible second materials include both woven and non-woven forms.
By woven is meant textiles such as fabrics, cloth, yarns, weaves, knits, felts, straps, belts, webs and the like.
By non-woven is meant forms including film, membrane, wrap, foil, foam, sheet, sheathing, tissue, overlay, stretch and shrink wrap products, and the like.
Barbs can readily engage non-wovens in single and multiple layers by piercing.
By particles is meant beads, pellets, powder, grains, dust, flock, chopped fibre, strands, wool-like, fluff, fibrefill, and the like, which can be used either in a dry form or with a liquid carrier such as a slurry.
By thermoplastic is meant any of a large variety of "plastic" polymers that liquefy when heated so as to wet the barbs, and solidify when cooled into a hard solid locked onto the barbs.
Thermoplastics include polypropylene, polyethylene, polyamide (such as Nylon), polyester,

7 acrylic, PVC, and ABS and the like, and hot melt adhesives which are often a mixture of different thermoplastics, waxes and the like.
By pre-preg is meant composite fibres of glass, carbon, etc., woven into a cloth fabric and pre-impregnated with liquid resin (such as epoxy) that has been partially cured to a semisolid. As such, they are flexible and dry to touch and can be draped, laid, impaled, or chop-sprayed onto the barbs. When heated, the resin re-liquefies to wet the barbs and as it cools, it becomes a hard solid whereby its fibres and adjacent barbs are locked together into a laminate.
By cements is meant slurries and suspensions that coalesce and harden by hydration or by carbon dioxide absorption or the like.
It is contemplated that any of the above may be used in any appropriate combination to make a precursor laminate and any resultant laminate and/or composite.
Next are described methods of composite fabrication from precursor laminate.
To make a composite, individual components are cut and/or formed from precursor laminate. During such forming, the barbs may be clinched to further secure the two materials together. The mechanical attachment provided by the barbs keeps the two materials together while handling, forming and assembling the precursor laminate. Alternatively the first material can be cut into components to which the second material is then applied to make precursor laminate components.
The components are first arranged as per the design to create a "loose"
composite assembly. Springs, clamps or weights may be needed to maintain intimate contact. Next the assembly is processed according to the nature of the second material by heating and cooling it to transform it into a hard solid. The entrapped, embedded, enrobed barbs of adjacent components are thereby locked together and a one-piece, rigid composite structure is the result.
In this way a composite is created in a simple, fast, low-cost operation.
By way of example, a composite panel has components made from precursor laminate of sheet metal and polypropylene fabric. Its core includes an array of truss-shaped components of precursor laminate which are laid side-by-side on a bottom skin of precursor laminate, after which an upper skin of precursor laminate is laid on top. Using weights or spring clamps, the entire

8 =
assembly is heated by oven, heat lamps, inductive means, or hot air. Hot air offers the benefit of internal and external heating by blowing through the open-ended trusses.
Heating continues until the thermoplastic polypropylene flows and wets the barbs. After cooling, the polypropylene becomes a hard solid which has entombed barbs of adjacent components locking them together into a rigid composite panel.
In the case of a particulate thermoplastic, the particulate thermoplastic (e.g. in powder or bead form) may be simply poured into the available cavities to fill them and then heated.
Alternatively the powder may be applied electrostatically (powder coating) to the individual components.
As another example, a precursor laminate cylinder may be assembled by forming an inner skin on a cylindrical mandrel with barbs facing outwards. This is wrapped with a thernioplastic fabric strap which is then wrapped with another layer (skin) of first material with the barbs facing inwards. The assembly is removed from the mandrel and heated to melt the thermoplastic fabric. When cooled the hard solid thermoplastic with embedded barbs locks the skins together into a composite cylinder (tube or pipe).
The instant precursor laminate comprises at least two layers: a sheet of a first ductile material 1 having at least one face populated with barbs 3, and a non-rigid heat-fusible second material 5 that is situated on at least one textured face of the sheet of first material. The second material 2 conformably engages and surrounds the barbs of the first material.
The precursor laminate can then be used for forming a laminate by heating and cooling the second material to cause it to harden around the barbs, thereby causing the second layer to be retained in attachment with the first layer. For example a thermoplastic fabric can be impaled on the barbs and then melted to wet the barbs. When cooled the two materials become laminated.
Turning now to the figures, Figure 1 shows a first material 1 with a single barb 3 rising up from a groove ploughed in first material 1 by a tool tip. The first material 1 may be any machinable or ductile material such as metal or thermoplastic, but not friable materials such as glass or concrete and the like. Figure la shows a row of barbs 3 on one face of a sheet of ductile material 1. The barbs may be produced in rows so that the barbs in adjacent rows point in opposite directions (not shown).

9 Figure 2a shows how barbs 3 may have different tip configurations - spike tip 3a and hook tip 3b, or both. In addition both barb tip types can be rolled, punched or pressed to deform the whole barb or the barb tip.
In Figure 2 the second material 5 (e.g. polypropylene fabric) has been impaled on the barbs so that the layers are mechanically attached to each other. The fabric's fibres move aside to allow the barb's entry resulting in the fabric conformably engaging and surrounding the barbs to form a precursor laminate 31 in its most elemental form - one layer of each material. Figure 2a shows first material 1 with rows of barbs 3 on both faces and having a fabric-type second material 5 engaging the upper barbs 3 and a film-type second material Sc engaging the lower barbs and being pierced by barbs of the lower face. The upper barbs 3 have clinched tips 3b which act as "heads" to more securely engage and retain the fibres of the second material 5.
A primary function of the second material 5 is to temporarily attach or join first materials to make a precursor laminate which can be handled, formed and assembled. After assembly, the second material or materials can be melted to wet and flow onto the barbs which, when cooled, transforms the second material layer(s), such as a conformable thermoplastic, into a hard solid locking the barbs together. Figure 15 shows two outer layers or skins of first material 1 whose barbs have been locked together by the melting and cooling of second material 5a. The layers are thereby bonded together with each other in a laminate.
Figure 3 shows first and second materials 1, 5 in planar juxtaposition ready to be assembled into a precursor laminate 9. Each of the two outer layers of second material 5 may be a textile (e.g., fabric or cloth), which engages barbs on the surfaces of first material 1. Figure 4 shows the resultant precursor laminate 9 after the outer layers have been heated and solidified.
Figure 3a shows another arrangement where precursor laminate 30 has outer skins of first material 1 with inward facing barbs 3 sandwiching a layer of second material 5.
Figure 4a shows the three layer precursor laminate 30 - two outer skin layers of first material 1 sandwiching a core layer of second material 5 into which the barbs are embedded.
Figure 5 shows a precursor flat "V" truss 10 made of precursor laminate 9, several of which will become the core layer of a composite panel.

Figs 6, 7 and 8 show alternate truss profiles, being rounded corrugate 10a, squared corrugate 10b, and "V" corrugate 10c, respectively.
Figure 9 shows a skin 31 with first and second materials mated into a precursor laminate skin 11 for a composite panel that has an edge folded into a flange 6, without delamination. Some or all barbs may be clinched during the folding operation.
Figure 10 shows the assembly 12 of truss cores 10 laid on a precursor laminate skin 11.
End trusses 10d are different in that they have a right angle bend that will become a panel connector. Although burrs 3 are labeled where they would be, they have been omitted for clarity.
Figure 11 shows the final assembly of the truss-cored composite panel 12 with skins 11 and multiple truss cores 10. Flanges 6 are shown adjacent truss component 10d which has a right angle facing the outside. This enables a narrow gap to the shin flange to be created during assembly.
The assembled panel 12 is then heated to a temperature sufficiently high to modify the second material 5 so that it wets-out adjacent barbs and adjacent surfaces (Figure 15). After cooling, the second material 5 coalesces into a hard solid 5a (Figure 15) locking the barbs of panel components 10, 11 together into a one piece, novel composite panel 21.
In Figure 12 three separate panels 12 are shown being joined by means of their end flanges 6 and gaps 8.
In Figure 13 is shown a curved panel 14, a variation where the precursor laminate 9 is curved. Such material may be used, for example, as a roof.
Figure 14 shows how a loose fibre 5b engages barbs 3 on bottom face of first material 1 and how it can be combined with fabric 5 as a two-layer layer.
Fibre 5b may be thermoplastic or it may be glass, carbon or other non-melting additive added to alter the physical properties of the instant laminate by providing known tensile strength to the matrix in which it becomes embedded when second material 5 melts and coalesces on cooling.
It should be understood that the above-described embodiments of the present invention, are only examples of implementations, merely set forth for a clear understanding of the principles of the invention. Many variations and modifications may be made to the above-described embodiment(s) of the invention as will be evident to those skilled in the art.
Where, in this document, a list of one or more items is prefaced by the expression "such as" or "including", is followed by the abbreviation "etc.", or is prefaced or followed by the expression "for example", or "e.g.", this is done to expressly convey and emphasize that the list is not exhaustive, irrespective of the length of the list. The absence of such an expression, or another similar expression, is in no way intended to imply that a list is exhaustive. Unless otherwise expressly stated or clearly implied, such lists shall be read to include all comparable or equivalent variations of the listed item(s), and alternatives to the item(s), in the list that a skilled person would understand would be suitable for the purpose that the one or more items are listed.
The words "comprises" and "comprising", when used in this specification and the claims, are used to specify the presence of the recited elements, and do not preclude, nor imply the necessity for, the presence or addition of one or more other elements.
The scope of the claims that follow is not limited by the embodiments set forth in the description. The claims should be given the broadest purposive construction consistent with the description as a whole.

Claims

What is claimed is:

1. A precursor laminate comprising (a) a first layer comprising a ductile material having a face textured with a plurality of barbs, and (b) a second layer comprising a heat-fusible material disposed on the textured face of the ductile material, wherein the heat-fusible material has a melting point, and when the heat-fusible material is heated to at least the melting point, the heat-fusible material at least partially melts so as to wet and surround a plurality of the barbs so that when the heat-fusible material is subsequently cooled and solidified, the ductile material and the heat-fusible material are locked together to form a laminate.

2. The precursor laminate of claim 1, wherein the first and second layers are mechanically attached together.

3. The precursor laminate of claim 1, wherein the first layer is a sheet of ductile material.

4. The precursor laminate of claim 3, wherein the ductile material is steel.

5. The precursor laminate of claim 3, wherein the heat-fusible material is a thermoplastic material, and the second layer of the precursor laminate is pressed onto the textured face of the sheet of ductile material so that a plurality of the barbs pierce the thermoplastic material.

6. The precursor laminate of claim 3, wherein the sheet of ductile material has upper and lower faces, each face textured with a plurality of barbs, the second layer being mechanically attached to the upper face, the precursor laminate further comprising a third layer comprising the heat-fusible material mechanically attached to the lower face, wherein when the heat-fusible material in both the second and third layers is heated to at least the melting point, the heat-fusible material at least partially melts so as to wet and surround a plurality of the barbs on each of the faces so that when the heat-fusible material is subsequently cooled and solidified, the ductile material and the heat-fusible material are locked together to form a laminate.

7. The precursor laminate of claim 1, wherein the heat-fusible material is fibrous.

8. The precursor laminate of claim 1, wherein the heat-fusible material is at least one layer of film.

9. The precursor laminate of claim 1, wherein the heat-fusible material is a particulate.

10. The precursor laminate of claim 1, wherein the heat-fusible material is pre-preg.

11. The precursor laminate of claim 3, wherein the first layer is substantially flat.

12. The precursor laminate of claim 1, wherein a plurality of the barbs are clinched.

13. A precursor laminate comprising:
(a) first and second layers, each layer comprising a substantially flat sheet of a ductile material having a face textured with a plurality of barbs; and (b) a third layer of heat-fusible material positioned between the first and second layers in engagement with the textured face of each of the first and second layers so that the heat-fusible material surrounds a plurality of the barbs on both the first and second layers, wherein the heat-fusible material has a melting point, and when the heat-fusible material is heated to at least the melting point, the heat-fusible material at least partially melts so as to wet and surround a plurality of the barbs so that when the heat-fusible material is subsequently cooled and solidified, the ductile material and the heat-fusible material are locked together to form a laminate.

14. A composite panel comprising at least one panel component made from the precursor laminate of any one of claims 1 to 13.

15. A method of forming a laminate comprising the steps of:
(a) providing a precursor laminate comprising a first layer comprising a sheet of a ductile material having a face textured with a plurality of barbs, and a second layer comprising a heat-fusible material disposed on the textured face of the sheet of ductile material, the heat-fusible material having a melting point;

(b) heating the heat-fusible material to at least the melting point to cause the heat-fusible material to at least partially melt so as to wet and surround a plurality of the barbs; and (c) allowing the heat-fusible material to cool and solidify so that the ductile material and the heat-fusible material are locked together to form the laminate.

16. A method of forming a laminate comprising the steps of:
(a) providing a sheet of a ductile material having a face textured with a plurality of barbs;
(b) attaching a heat-fusible material to the textured face of the sheet of ductile material, the heat-fusible material having a melting point;
(c) heating the heat-fusible material to at least the melting point to cause the heat-fusible material to at least partially melt so as to wet and surround a plurality of the barbs; and (d) allowing the heat-fusible material to cool so that the ductile material and the heat-fusible material are locked together to form the laminate.

17. The method of claim 16, wherein the heat-fusible material is in the form of a sheet, and attaching the heat-fusible material to the textured face of the sheet of ductile material comprises pressing the sheet of heat-fusible material against the textured face of the sheet of ductile material so that a plurality of the barbs enter the sheet of heat-fusible material.