CA3006619A1

CA3006619A1 - Improvements to a fiber metal laminate and a method of production thereof

Info

Publication number: CA3006619A1
Application number: CA3006619A
Authority: CA
Inventors: Farid Taheri
Original assignee: Individual
Current assignee: Individual
Priority date: 2015-12-15
Filing date: 2015-12-15
Publication date: 2017-06-22
Also published as: WO2017100900A1

Abstract

A new fundamentally 3D fiber metal laminate (3DFML) has been developed by employing a combination of a unique 3D fabric, whose cavities are foam-filled and lightweight noncorrosive thin metallic sheets that render a series of unique component materials with mechanic performance significantly superior to current 2DFMLs and lightweight sandwich core composite materials.
Flexural stiffness and impact properties are improved through the use of the fabric and the foam infill that provides significant stability to the pillars of the 3D
fabric of the new material.
A new type of structural laminate can be formed by bonding together two or more of the new component laminates or component articles. The new laminate and component laminate are suitable for use in automobiles, marine vessels, other modes of transportation, holding tanks, alternative energy structural parts and other applications particularly requiring optimal impact resistance and minimization of delamination occurrence.

Description

IMPROVEMENTS TO A FIBER METAL LAMINATE AND A METHOD
OF PRODUCTION THEREOF
Abstract A new fundamentally 3D fiber metal laminate (3DFML) has been developed by employing a combination of a unique 3D fabric, whose cavities are foam-filled and lightweight noncorrosive thin metallic sheets that render a series of unique component materials with mechanic performance significantly superior to current 2DFMLs and lightweight sandwich core composite materials.
Flexural stiffness and impact properties are improved through the use of the fabric and the foam infill that provides significant stability to the pillars of the 3D
fabric of the new material.
A new type of structural laminate can be formed by bonding together two or more of the new component laminates or component articles. The new laminate and component laminate are suitable for use in automobiles, marine vessels, other modes of transportation, holding tanks, alternative energy structural parts and other applications particularly requiring optimal impact resistance and minimization of delamination occurrence.
Description FIELD OF THE INVENTION
The present invention relates to a novel 3D fiber-metal laminate comprised of mutually 3D foam-filled fiber-reinforced composite fabric, interlayered with metallic alloy sheets. More specifically, the invention relates to a 3D fiber-metal laminate made with a unique 3D fabric, whose though-thickness cavities are filled with a lightweight foam, which provides significant stability to the vertical pillars of the fabric, thus rendering an exemplary stiff and lightweight hybrid material.
BACKGROUND OF THE INVENTION
Fiber-reinforced composites offer considerable weight advantage over other materials, such as metals. Generally, the weight savings are obtained at the sacrifice of other important material properties such as; ductility, toughness, 0,3 bearing strength, conductivity and cold forming capability. In order to overcome a.

these deficiencies, new hybrid materials called fiber-metal laminates have been developed to combine the best attributes of metal and composites.
Fiber-reinforced polymer (FRP) composites have been extensively utilized in various industries over recent years. The relatively high specific-strength and stiffness and noteworthy fatigue and corrosion endurance characteristics have made them useful materials for numerous applications, particularly in automotive fabrication. The weakest link in the FRPs has been their inter-laminar shear capacity, which makes them susceptible to impact loading. Thus, previous researchers have tried to improve the impact resistance of FRPs over the last over the last few decades. One of the most effective means of improving the impact resistance of FRPs has been to incorporate thin sheets to form so-called fiber-metal laminates (FMLs).
WO 2007/145512A1 discloses a FML comprising metal plates with an individual thickness of lmm. Patent EP0312150 A1 and EP0312151 describe other useful FMLs. US Patent 7,446,064 B2 (Hanks et al, Nov 2008) employs a glass fabric reinforcing layer and a polymer core but no 3D fabric and uses aluminum alloy instead of lightweight magnesium alloy.
US Patent 6,824,851, Locher et al. (2004) describes panels utilizing a procured reinforced core and method of manufacturing the same. It describes a flooring assembly comprised of a plurality of sandwich panels. Also, it claims a procured core that has a plurality of phenolic ribs and foam strips positioned in an alternating fashion. The prior invention core is manufacture by impregnating a layer of fabric with phenolic resin between two foam cones and stacking them in similar alternating fashion to create a bun. The bun is cured at a constant pressure and temperature and cooled. The bun can be cut along a perpendicular plane to provide a procured reinforced core panel that is ready to be inserted as a core in a sandwich panel. The present 3DFML invention uses a unique 3D fabric, whose performance is improved by the injection of a lightweight foam and interlayering of lightweight metal sheets. This new hybrid material is fundamentally different in configuration, materials used, and its performance compared to the prior art by Locher.
US patent 8,334,055 B2 is a typical sandwich type composite with the exception that it uses 2D fabric, as opposed to our unique 3D fabric, which has through-thickness fibers (pillars), which provides comparatively much greater overall rsj az, ra a_ stiffness, but more significantly, greater local stiffness and strength, which creates greater impact strength of the 3D fabric, and its 3DFML.
Impact characterization of FMLs with aluminum as the constituent metal has been previously investigated resulting in several patents. GLARE (Laminate Aluminum Reinforced Epoxy, US Patent 5039571 A) FML, is composed of several very thin layers of metal (usually aluminum) interspersed with layers of glass-fiber "pre-preg", bonded together with a matrix such as epoxy. GLARES FMLs were developed with emphasis upon the effects of FML thickness and impactor mass on the impact response. It was determined that specimen thickness had a significant effect upon the failure modes of FMLs, such that an increase in panel thickness significantly enhanced the energy absorption capacity of the FMLs.
US Patent 4,500,589 describes the material under trade name ARALL, which is fabricated by putting fiber reinforcement in the adhesive bond lines between aluminum alloys. The main difference between ARALL and GLARE was that GLARE consists of glass fibers instead of the ARALL aramid fibers and that GLARE exhibits higher tensile and compressive, greater impact behavior and greater residual strength than ARALL. Currently, GLARE materials are commercialized in six different standard grades based upon unidirectional glass fibers embedded with epoxy adhesive resulting in pre-pregs with a normal fiber volume fraction of 60%. It has been found that ARALL exhibits poor compressive strength, which represents a major limitation. CARAL materials have exhibited an improvement over ARALL materials, such that they contain different amounts of carbon/epoxy pre-pregs instead of amarmid/epoxy pre-pregs.
Compared with aramid/epoxy, the carbon/epoxy composites possess higher specific modulus, but relatively low values of specific impact strength and strain to failure. In terms of fatigue, it was recognized that aramid fiber composites exhibit better low cycle fatigue performance but worse high cycle fatigue performance than carbon fiber composites. Moreover, the high stiffness of carbon fibers allows for extremely efficient crack bridging and therefore very low crack growth rates.
Fiber-metal laminates or FMLs, such as described in US 4,500,589. For instance, are obtained by stacking alternating sheets of metal (most prefer aluminum) and the fiber-reinforced pre-pregs and curing the stack under heat and pressure, for example, in ships, cars, trains aircraft and spacecraft. They can also be used as sheets and/or a reinforcing element and/or and or as a stiffener for (body) çn 0,) structures of these transports, like for aircraft for wings, fuselage and tail panels and/or skin panels and structural elements of aircraft.
3D fiberglass (3DEG) fabric (ex. Patent US 6338367 B1) is a newly developed fiberglass woven/braided fabric consisting of two bi-directional woven fabrics knitted together by vertical braided glass pillars. Besides glass fibers, carbon and even basalt fibers as well as hybridizations of these fibers could be used to form 3D clothes. The unique configuration of fibers in 3D clothes have been claimed to provide excellent impact resistance. Although this fabric and alike (i.e., z-pinned fabrics) are referred to as 3D, they really are not truly 3D fabric in comparison to the 3D fabric used to produce the 3D FML of our invention. The 3D fiberglass fabric of Patent US 6338367 B1 has 2D overall geometry, but with fibers running along the third dimension. In the 3D fabric used in our invention, there are numerous pillars running along the third dimension that separate the top and bottom 2D fabric by distance from 2-10 mm, thereby creating cavities that can be infilled with a lightweight foam; therefore, the configuration is truly 3D.
Polyurethane liquid foam is comprised of a two-part liquid that yields a high strength, rigid, closed-cell foam for cavity filling and buoyancy applications. The liquid is extremely simple to use. Immediately after mixing the two component parts, it is poured into cavities, then left to cure quickly. The foam imparts considerable stiffness with only minimal increase in weight. Optimal results require use of appropriate mixing procedures. The majority of foam use is behind other materials for domestic and commercial uses, such as constructing furniture and preparing thermal insulation panels for the building industry.
US Patent 5547735 (Roebroeks, 1996) describes a metal-polymer laminate that has a bidirectional reinforcing layer containing roughly 45-70 volume per cent high strength glass fibers. The bidirectional reinforcing layer includes a center layer containing glass fibers oriented generally parallel to a first direction and first and second outer layers each reinforced with glass fibers oriented in a second direction extending generally transverse to the first direction. The bidirectional laminate is suitable for use in aircraft flooring and other applications requiring improved impact strength. The prior patent differs considerably from the current patent since it used 2D fabric, where the present invention uses 3D fabric, with foam filling the cavities of the 3D fabric. As stated, the present 3DFML invention is multi-dimensional, which is a major improvement over the 2D prior invention that results in much improved stiffness and strength properties over the prior patent. In a.

addition, it provides much greater local performance under an applied load, specially, an impact load.
Prior patent W02005075189 A2 (LeGall, 2005) describes lightweight composites that display high flexural strength and are comprised of; epoxy foam sandwiched between two layers of facing material that form sheets, which can replace steel structures. This prior patent employs or carbon fibers as a fabric material, which is preferably embedded into the epoxy matrix. It also mentions box structures or concentric metal tubes, both elements that do not appear in the present patent. The prior patent involves preparing a sandwich-type structural material by impregnating a fiber layer with epoxy resin, then heating the foam to cure the epoxy or extruding the foam material between the surface layers.
The present 3DFML invention represents a significant improvement to the sandwich composite introduced by LeGall, 2005. The main difference is the use of unique 3D fabric. The 3D fabric has large cavities through its thickness, separated by great numbers of pillars, which can be filled with a lightweight foam. Not only does the foam provide stability to the bi-directional fabrics that are placed on the top and bottom faces of the foam layer, but it also provides stability to the pillars that are fundamentally unique to the present 3D fabric. The enhanced stability provides much greater stiffness and strength than a foam provides in the case of typical sandwich composites (i.e., the invention of LeGall, 2005). The performance of the invented 3DFML is much more superior to that created by LeGall, 2005, especially under impact loading. Moreover, the 3DFML provides much greater through-thickness shearing strength in comparison to the prior art.
US Patent 7,446,064 (Hanks et al, 2008) describes a composite building panel comprised of a fiber-reinforced sheet between a metal skin and the panel core.
The reinforcing sheet is preferably made of aramid fibers that improve the impact resistance and penetration resistance of the building panel.
The present 3DFML invention is significant improvement to the panels invented by Hanks et al, 2008. The main difference is the vertical pillars of the fabric.
These pillars provide much greater through-thickness strength, especially when surrounded by polymeric foams. In addition, they produce much greater through-thickness shearing strength in comparison to the prior art.
The use of lightweight magnesium alloys in various engineering applications has been increasing steadily in recent years, especially in the automotive industry. One Lic?,_ of the primary reasons is due to the low density of magnesium (roughly 25%
that of steel and 35% lower than aluminum, which makes the weight of magnesium alloy structural components very comparable to that of FRPs. Magnesium alloy-based fiber metal laminates exhibit several advantages over other metal base complexes such as; a high strength to weight ratio, improved electromagnetic shielding capability, relatively density and lower cost compared to aluminum and superior corrosion resistance. Previous studies have found that compared to T3-based GLARES, the impact resistance of magnesium-based FMLs was lower than that of GLARES when damage in the form of cracking of magnesium plates was taken as the failure criterion. However, when comparing the perforation limit, the specific impact energy of the magnesium-based FMLs was observed to be approximately equal to GLARES.
In addition, it has been found that lightweight materials like magnesium-based alloys exhibit higher specific tensile strength than aluminum-based FMLs. Also the specific tensile strengths of magnesium-based FMLs has been found to be higher than that of 2024-TO aluminum alloy-based FMLs. It has also been suggested that the relatively lower elastic modulus and fracture properties exhibited by magnesium-based FMLs may be mitigated by selection of an appropriate volume of the composite constituents. One of the most common modes of damage for conventional FML configurations subjected to low velocity impact is the delamination that could develop within their FRP layers and/or within FRP/metallic interfaces.
Patent CN 104385714A, fiber reinforcement magnesium alloy laminated plate and manufacture thereof describes a fiber reinforcement magnesium alloy laminated plate, which is comprised of several magnesium alloy plates arranged upon one another in position that ultimately improve the tensile strength, ductility and anisotropy of the resulting plate.
The present invention relates to the development of a 3D fabric and improvements to fiber a metal laminate as a 3D fiber metal laminate (3DFML) and to a process for their manufacture. In particular, the present invention relates to high strength to weight ratio, somewhat flexible composite materials and their manufacture. The invention further relates to the production of high strength to weight articles such as FMLs. Steel and aluminum are often used to produce articles that exhibit strength or are lightweight, but neither exhibit exceptional strength and are also lightweight.
LID
to ro The inventor has found that the lightweight, more rigid fiber metal laminate composites of the present invention are particularly useful as materials in the automotive, aircraft and other transportation modes and power production industries where they may be used to replace metal and glass-reinforced plastic articles and weaker fiber metal laminated bodies, airplane structural components, wind turbine blades and various parts of ships such as hatch covers. In recent years, there has been a trend to replace metal components with composites and composites with fiber metal composites and move towards lighter materials with similar strength and more flexibility, which aids in the manufacturing stage and when developing and applying various produced articles. These newer materials have been represented by materials such as; aluminum, fiber reinforced polymeric materials, foam materials, composites containing foamed layers and composites containing metal layers. However, there is an ongoing need for new materials that exhibit increased strength, reduced weight and increased flexibility.
The composites of the present invention portray a variety of uses in additional applications in which high strength to weight ratio is deemed important along with a high degree of flexibility to enable various parts to be produced in a manufacturing process, while acting as a substitute for steel, aluminum and other fiber metal laminates in production of parts for automobile, airplane, land and marine transport and power industry applications. Other particular uses as a substitute for steel and aluminum include for railway cars and storage tanks in the water resources, petroleum and petrochemical industries, The present 3DFML invention is significant improvement to the fiber reinforcement magnesium alloy laminated plate in the abovementioned patent (CN

104385714A). The main difference is the use of the unique 3D fabric. The 3D
fabric has large cavities through its thickness, separated by great numbers of pillars, which can be filled with a lightweight foam. Not only does the foam provide stability to the bi-directional fabrics that are placed on the top and bottom faces of the foam layer, but it also provides stability to the pillars that are fundamentally unique to the present 3D fabric. The enhanced stability provides much greater stiffness and strength than those presented by the fiber reinforcement magnesium alloy laminated plate of the abovementioned patent (CN 104385714A).
The performance of the invented 3DFML is much more superior locally. Testing conducted by the inventors of the present invention has shown that due to the (1 I
OD
a_ presence of the pillars of the new 3D fabric, delamination, which is common to fiber reinforcement magnesium alloy laminated plate of the abovementioned patent (CN 104385714A), is minimized. This prior material is produced by hot press molding, a quite different process compared to the production of the present invention.
OBJECTIVES OF THE INVENTION
The prime objective of this invention is to introduce a novel application of an existing 3D fabric to form a newly fundamentally 3 dimensional fiber metal laminate (3DFML). This includes showing that the properties of this new 3DFML
are significantly more superior to conventional FML materials. The agent that provides the superior properties, especially when material is subjected to impact is the presence of the vertical pillars (hereafter referred to as "pillars", which is unique to the 3D fabric used to form this FML. This 3DFML, of which can be configured in different combinations (some of which are illustrated in the Figures herein) are the first appearance of a 3DFML know to the inventor. These 3DFMLs provide specific stiffness and strength (i.e. stiffness and strength values normalized with respect to the weight of FML and impact energy absorbing capacity, which is significantly greater than that offered by present 2DFMLs and various types of sandwich composites. The pillars also enhance the failure modes of their unique 3D FMLs, in that they prevent delamination that is usually encountered as the weakest link in 2DFMLs.
It is an object of the invention to present a novel application of an existing fabric to form a unique 3D fiber metal laminate with varying configurations that offer unique properties that differ notably from current 2DFMLs or sandwich type composites. It is a further object of the invention to provide a laminate comprised of a 3D fabric, with its vertical cavities filled with foam, interlayered with lightweight metallic alloys. Moreover, additional different types of 2D cloth (such as carbon, ceramic, basalt, etc.) can also be used adjacent to the 3D fabric to provide even more stronger 3DFML. Another objective is to describe a method of producing this new 3DFML.
Another objective of the invention is to show that the unique configuration of fabric, foam, adhesive and lightweight alloy sheets will enable assembly of superior low velocity impact resistant laminate materials.
ao Another object of the invention is to show that the performance of the FMLs comprised of 3D fabric, foam, adhesive, lightweight alloy sheets and optional cloth materials will minimize delamination that could occur within laminate layers and/or within fabric/metallic interfaces.
Another object of the invention is to advise of uses of such laminates as a structural part or article, particularly in land sea and air modes of transport, liquid holding tanks and alternative energy structures.
Additional objects, features and advantages of the invention will be set forth in the description, which follows and in part will be obvious from the description or may be learned by practice of the invention. The objects, features and advantages of the invention may be realized and obtained by means of the instrumentalities and combination particularly pointed out in the appended claims.
SUMMARY OF THE INVENTION
A structural 3D fiber-metal laminate (3DFML) is described that in one of its configurations has a layered composition of first and second metal alloy sheets as opposing outer layers to a 3D fabric that has cavities, which are filled with a lightweight foam.
In another aspect, liquid resin is applied to a 3D fabric, which creates expansion of the through-thickness fibers of the fabric, which in turn creates spacing and cavities in the body of the 3D fabric core. The cavities are then filled with a lightweight polymeric foam.
In another aspect, the foam injected 3D fabric layer is fitted between the opposing metal alloy sheets and bonded to the sheets using an adhesive/resin.
In another optional aspect, one or more thin layers of cloth is fitted between the 3D
fabric layer and metal alloy sheets on one or opposing sides and bonded to the fabric layer and sheet layers using the same resin used to form the 3D and optional 2D fabrics.
In yet another aspect of the invention, a method of fabrication of a hybrid structural 3D fiber metal laminate from the 3D fabric, foam and metallic alloy components is provided.
C3) ol) co a_ The Steps involved in the method of producing the improved 3D fiber metal = laminate and representative of the present invention comprise;
1) Step one involves sanding the surfaces of metal alloy sheets, blowing surfaces clean and wiping with acetone.2). Step two involves applying a liquid polymeric resin onto 3D fabric and its core fibers and permit to cure with addition of a hardener. 3) Step three involves injecting a liquid polymer foam (or alike) into the 3D fiber core and permitting it to solidify. 4) Step four involves the option of bonding a layer of various types of cloth to the top and bottom the foam injected 3D fabric core layer. 5) Step five involves applying adhesive/resin to the inside faces of the outer metal alloy sheets to the mating sides of the 3D core for bonding the constituents together. 6) Step six involves bonding two or more 3D fiber metal laminates together using an adhesive material to form a combination of 3D
fabric metal alloy laminates or an article.
Needless to mention, in all the above description of the 3D fiber metal laminate assembly, other completing operations of the process will be carried-out at the appropriate moments within the fabrication process to produce a satisfactory hybrid laminate component of the required specifications. It will be apparent to those skilled in the art that it is possible to alter or modify the various details and steps of this invention without departing from the spirit of the invention.
Therefore, the foregoing description is for the purpose of illustrating the basic idea of this invention and it does not limit the claims which are listed in this patent.
BRIEF DESCRIPTION OF THE FIGURES
The invention is described in reference to the following illustrations.
Figure 1 is a front view of a 3D fabric material with applied resin according to an embodiment of the present invention.
Figure 2 is a front view of 3D fabric material with applied resin and foam injected into its through-thickness cavities, forming a layer within the 3D fabric material laminate according to an embodiment of the present invention.
Figure 3 is a front view of 3D fabric material with applied resin, injected foam forming a layer within the 3D fabric, optional cloth layers and outer lightweight alloy sheet layers that bonded together by epoxy resin, forming a 3D fabric laminate according to an embodiment of the present invention.
ca_ Figure 4 is a front view of two 3D fabric laminates bonded together to form a fabric laminate component.
Figure 5 is a depiction in graphical form of the residual deformation of a 3D
fabric laminate test specimen, corresponding to various failure modes being compared to woven fabric test specimens having several different layers (e.g. 4, 7 and 16 layers, respectively).
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS OF
THE INVENTION
In the following description, reference is made to the accompanying drawings, which form a part hereof, and which show, by way of illustration, specific embodiments in which the invention may be practiced. The present invention, however, may be practiced without the specific details or with certain alternative equivalent methods to those described herein. The method of producing an innovative 3D fiber metal laminate component using a 3D fabric injected with foam between thin sheets of lightweight alloy, with or without a fiber cloth layer reinforcing layer, will now be described in reference to the above stated drawings.
The working principle of the hybrid 3D laminate component will be described first and then the particular way of fabricating the 3D laminate component will be described.
In the description of the present invention and elsewhere, the 3D fabric light-weight alloy sheet laminate may occasionally be called a laminate or laminate component or FML (fiber metal laminate) or 3D fiber metal laminate (3DFML) or 3D fabric metal alloy laminate or 3D fabric laminate or 3D laminate or fabric metal laminate or similar for the sake of brevity, while still maintaining the accuracy and intent of the description and the spirit of the present invention.
The basis of the present invention is a unique arrangement of 3D fabric-reinforced composite layers, lightweight alloy metal sheets, with additional layers of different cloth if desired, foam and adhesive. In accordance with the invention, a 3D
fabric metal alloy laminate is provided comprised of fiber-reinforced composite layers and lightweight alloy metal sheets. It has been previously stated in this submission that the preferred 3D fabric for the invention is 3D glass fabric (due to its relatively lower cost and good mechanical properties), although other types of 3D fabrics a) could be employed to achieve potentially similar or more superior results. It has 0_ also been previously stated in this submission that other types of 2D fabrics can be used in conjunction with the 3D fabric to obtain more improved performance in this invention.
The present invention comprises the assembly of a new 3D fiber metal laminate as a component or article and a new 3D fiber metal laminate component by bonding together two or more of the new 3D fiber metal laminates. More specifically, the new 3D laminate is comprised of a 3D fabric layer(s), and optional different types of fabric layer(s) bonded to one or either side of the 3D layer inter-placed with lightweight alloy sheets bonded to the 3D layer or the optional additional layers.
The 3D fabric material is impregnated with epoxy resin (adhesive) and in addition, a lightweight foam is injected into the cavities of the 3D layer(s), which in plurality forms a complete layer of 3D fabric, which improves the performance of the 3D
layer. Optional 2D fabric layers are bonded to the 3D layer using the same resin used to impregnate the 3D fabric.
In the present invention, fiber-reinforced composite layers preferably comprised of 3D fabric treated with a resin, infilled with a lightweight foam, layers of lightweight thin metallic alloy form a novel 3D fiber metal laminate. The preferred epoxy resin (adhesive) is applied to the 3D fabric, is also used to adhere the various layers of metals, cloth and 3D fabric material structures together.
The resin impregnated 3D fabric is first cured in an oven, and then its cavities are filled with a lightweight foam. Afterward, the metallic sheets are bonded to the cured foam-filled 3D fabric with the same resin, and again cured in an oven. The preferred range in thickness for a 3D fabric material is from 2 mm to 10 mm, thus the 3D

fabric laminate component can display various thicknesses dependent upon the thickness and number of layers of 3D fabric materials employed to assemble one new 3D fiber-metal laminate.
In the present invention, the laminate outer lightweight alloy sheet layers can be formed of one or more lightweight alloy sheets of varying thicknesses dependent upon the desired structural character or the application of the new 3D
laminate or new 3D laminate component. The preferred range for thickness of a single lightweight alloy sheet is 0.4 mm to 2 mm. The total thickness of a lightweight alloy sheet layer is contingent upon the number of sheets chosen to be employed for a particular design or application. In addition, the number of optional cloth layers employed in the new 3D laminate and laminate component can also vary CN
from one to more layers dependent upon the desired structural character or the aJ
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application of the new 3D laminate or new 3D laminate component. The preferred range for thickness of a 2D optional cloth is 0.2 mm to 0.4 mm. The total thickness of a cloth layer is contingent upon the number of units of cloth that are chosen to be employed in a particular design or application.
In the present invention, preferably, when applying adhesive to join two separate surfaces/layers of the 3D laminate and 3D laminate component, an appropriate amount of adhesive is applied to both surfaces to be joined simultaneously. It has been discovered by the inventors that 3D fabric metal laminates with described fabric properties have better structural properties respecting joint strength as well as in fatigue. In particular, a higher resistance against low velocity impact and fabric delamination than conventional fiber-metal laminates of which the relevant properties are not in accordance with the methods of assembling the present invention.
In accordance with the invention and Figure 1, 3D fabric (2) material is shown with its pillars (1) with impregnating resin (3) that creates cavities and spacing within the 3D fabric (2) material. Originally the pillars (1) are collapsed at a horizontal position. Once the resin (3) is applied to the 2D fabrics, the pillars are "awakened", transferring from a horizontal to vertical orientation, thereby separating the top and bottom 2D fabrics, creating the spacing and cavities in the 3D fabric.
In accordance with the invention and Figure 2, AZ31B lightweight alloy sheets (5) ranging in thickness from 0.4 to 2 mm are employed to form the outer layers of the new 3D fabric laminate and 3D fabric laminate component. The lightweight alloy sheets (5) as shown in Figures 2, 3 and 4 are sandblasted and treated with acetone to ensure clean surfaces for application of a bonding agent. Lightweight alloy is useful for its high strength to weight ratio, low density and corrosion resistance, all features useful in 3D fiber-metal laminate. Lightweight foam (4) material is injected into the 3D fabric (2) material to fill the cavities and to reinforce the strength and provide stiffness to the 3D fabric (2) material, and stability to pillars (1).
In addition, lightweight alloy sheets (1) are bonded with resin (adhesive)(3) to the outer sides of the 3D fabric (2) material to form the exterior covering for the new laminate component and to provide additional strength and stiffness to the laminate en component. The aforementioned epoxy resin (adhesive) (3) used as a bonding agent and impregnating agent are the same material in the present invention, to o_ although varying bonding agents could be employed, although perhaps not with the same optimal results. The resin is combined with a hardening agent to perform the curing process, thus the hardening agent is considered part of the epoxy resin or adhesive for the purposes of the present invention. The adhesive (3) dries in a matter of minutes, thus it is applied, and the layers bonded together while the new laminate is under vacuum pressurization, to ensure a strong bond. It was found from lab testing, respecting the present invention that the optimal thickness range of 3D fabric material (2) with resin (3) and foam (4), which form the core layer of the laminate or laminate component, is from 2 to 10 mm, with a preferred thickness of 4 mm to gain greater cost and impact integrity advantages.
In accordance with the invention and Figure 3, an optional step in the assembly of a 3D fabric laminate component is the insertion of a thin layer of 2D cloth (6) as a reinforcing layer between the interior 3D fabric core (2) layer and the outer lightweight alloy sheet (5) layer to increase strength and stiffness in the laminate.
The 2D cloth layer (6) is bonded to the core fabric (2) layer using adhesive (3) material. The fiber reinforcing (6) layer may be employed on one or both sides of the 3D fabric (2) and one or more lightweight alloy sheets (5) may be used on one or both sides of the 3D fabric (2) layer. A new 3D fabric (2) lightweight alloy sheet (5) laminate is assembled by bonding together using adhesive (3) all layers noted in Figure 3.
In accordance with the present invention and Figure 4, two 3D fabric (2) lightweight alloy sheet (5) laminates are bonded together with adhesive (3) to form a new 3D fabric (2) lightweight alloy sheet (5) laminate component. For the purposes of the present invention the new laminate component may be formed by bonding together two or more of the laminates with adhesive (2) material. All laminate layers are bonded together under vacuum pressurization or similar pressure application using adhesive (2) to ensure optimal bond strength and optimal structural characteristics of the present invention. Testing by the inventors has revealed that the new 3D fiber metal laminates combined exhibit superior structural properties to the new 3D fiber metal laminate alone.
In accordance with the present invention and Figure 5, there is displayed herein a graph depicting the residual deformation of the new 3D FMLs compared to conventional woven fabric laminates. The energy levels used for testing specimens were directed to generate damage: (i) on the impact surface (ii) to the reverse side and (iii) in the form of full perforation through test specimens. The three types of damage generated are depicted as mode 1, mode 2 and mode 3, respectively. In the present invention, testing has shown that due to the resilient structure of 3D

lightweight fabric, no delamination has occurred. In addition, it has been determined through testing that impact energy is absorbed mainly by the crushing of vertical pillars and the supporting foam beneath the region of impact, which leads to higher impact resistance exhibited by the 3D lightweight fabric metal alloy laminate and a smaller damage area, thus revealing a major improvement.
Low velocity impact response and failure modes for the present invention have been investigated experimentally and computationally by the inventor. The performance of the new 3D fabric metal laminates (3DFMLs) are compared to that of conventional FMLs (fiber metal laminates) made with various numbers of layers of biaxial woven fabrics. The failure modes of the new 3D laminate test specimens are characterized by being based upon the quantitative measurements of shape, type and extent of damage inflected upon the FMLs structure.
The impact characteristics of the newly assembled 3DFMLs are examined by characterizing and comparing their energy absorption capacities, residual deformation and maximum deformation due to low velocity impact. Test results reveal that the FMLs based upon the 3D fabric exhibit outstanding improvement in impact absorption capacity, although the impact energy resistance is lower than FMLs based upon woven fabrics. In addition, a finite element analysis (FEA) framework was constructed using the commercial finite element code ABAQUS to simulate the response of such complex structures. Results from running the FEA

demonstrate that the simulation framework can be used to optimize the configuration of 3D FMLs for different loading situations and provide a useful quality control check during 3D FML assembly. Results of laboratory testing by the inventor relevant to the present invention are summarized in the following Tables.
Table 1 displays a comparison of the flexural stiffness of FMLs made by existing industry woven fabric, compared to values for those made by the new 3D fabric FMLs particular to the invention. The comparison shows that the new 3D FMLs exhibit a notably improved performance on weight and material cost basis. The details of the FMLs noted in Table 1 are reported in Table 2.
LI) n3 o_ Table 1. Flexural stiffness of the FMLs Flexural Specific Flexural Specimen ID Stiffness Stiffness (N-(N-m2) in2ig.mm-3) 3DF-FML 269.28 5729.53 4-layer FML 178.23 1916.40 7-layer FML 356.96 2189.96 16-layer FML 1287.25 3460.34 Table 2. Specifics of the different FMLs Overall Overall Reinforcem Number of Specimen ID Thickness Density ent Fabric layers of (mm) (gimm3) type fabrics 3DF-FML 14.40 0.047 3DFGF 1 4-layer FML 4.87 0.093 biaxial= 4 woven 7-layer FML biaxial 6.53 0.163 7 woven 16=layer biaxial 10.16 0.372 16 FML woven The present invention also incorporates new research data that shows improvements exhibited by the 3D fabric lightweight metal alloy laminate relate a bending stiffness greater than conventional FMIs. Employing four layers resulted in flexural stiffness of the 3D fiber lightweight metal alloy fabric that was found to be greater than the previously mentioned biaxial woven layers of FRPs. It was also determined that the 3D fabric lightweight metal laminate could absorb the highest impact energy in comparison to the aforementioned woven layers of FRPs.
Many modifications may be made in the structures and processes to alter or modify Lo the various details of this invention without departing from the spirit and scope N-1 thereof, which are defined only in the appended claims. For Example, one skilled ca_ in the art may discover that a certain combination of components, i.e. a particular type of 3D fabric and foam, etc., may result in a 3DFML with certain advantages.
Further, certain dimensions or designs other than those disclosed herein could be produced for a particular installation, but fiber-metal laminates and laminate combinations of these designs or dimensions would nevertheless fall within the scope of the claims herein.
Needless to mention, in all the above described methods of 3D laminate and 3D
laminate combinations production, the other complementing operations of the assembly process will be carried out at the appropriate moments of the assembly to produce a satisfactory laminate of the required specification. It will be apparent to those skilled in the art that it is possible to alter or modify the various details of this invention without departing from the spirit of the invention. Therefore, the foregoing description is related for the purpose of illustrating the basic idea of this invention and it does not limit the claims which are listed herein.
We believe that using the combination of a 3D fabric and a suitable resin, with 3D
fabric's through-thickness cavities filled with a lightweight foam produces a hybrid material that exhibits much greater stiffness and strength than the conventional 2D
fiber-reinforced polymer composites, as well as greater local strength and through-thickness shearing strength than the conventional foam-cored sandwich composite materials. The combination of this 3D hybrid material with thin lightweight alloy metal alloy sheets produces a lightweight 3D fiber-metal laminate with mechanical performance superior to the conventional 2D fiber-metal laminates. The new 3DFML provides better performance under impact than the comparable 2DFML, 2D FRP and sandwich composites. Comparatively, the use of the 3D fabric also minimizes the delamination that is the Achilles heal of 2D FRPs and 2D FMLs.
What is believed to be the best mode of the invention has been described above.
However, it will be apparent to those skilled in the art that these and other changes could be made to the present invention without departing from the spirit of the invention. The scope of the present invention is indicated by the broad general meaning of the terms in which the claims are expressed.
The research employed herein was funded by the National Science and Engineering Research Council of Canada (NSERC) and AUT021, a Network Center of Excellence in automotive grant.
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References:
Low-velocity Impact Response of Fiber/Magnesium FMLs with a New 3D Glass Fabric, Zohreh Asaee, Shahin Shadlou and Farid Taheri, In Press.We Claim 1. A 3D fabric combined with lightweight metallic alloy sheets to form a new class of 3D fiber metal laminates and the method of producing this new 3D fiber metal laminate, each comprising: a resin cured 3D fabric layer(s); a resin coating residing upon the opposing surfaces of said 3D fabric layer(s); a foam used as a filler in the cavities of said 3D fabric layer(s); thin optional cloth layers laid adjacent to said 3D fabric; thin lightweight alloy sheet layers laid adjacent to said 3D fabric (or adjacent to said 3D fabric with optional layers of 2D fabrics) and an adhesive/resin to form a bond between all said layers.

2. The 3D fabric according to Claiml, wherein said core layer is comprised of said 3D-fabric, a surface coating of said resin upon opposing sides of said core, said core fabric fibers impregnated with said resin and foam injected into said fabric cavities in order to increase the structural strength and stiffness of said 3DFML, thereby forming a unique hybrid 3D fabric.

3. The 3D fabric according to Claimsl, 2 wherein said foam-filled 3D fabric may also be produced from other types of organic and inorganic fibers and hybrids of various fibers and different type foams.

4. The 3D fabric impregnated with resin according to Claims 1 and 2 wherein said resin may be epoxy, vinyl ester, polyester or alike in heat-cured or 2-part room-cured variations.

5. The 3D fabric according to Claims 1,2,3,4 wherein different thicknesses of said 3D fiber-metal laminate are formed by employing various thicknesses of said 3D

fabric, where said fabric will range preferably from 2mm to 10 mm in thickness.

6. The 3D fiber-metal laminate according to Claims 1,2,3,4,5 wherein 3D fabric cured with resin and filled with foam is combined with lightweight metallic alloy sheets to form a new class of 3D fiber metal laminates. 00 0.) la0 (13 Q.

Claims

References:
Low-velocity Impact Response of Fiber/Magnesium FMLs with a New 3D Glass Fabric, Zohreh Asaee, Shahin Shadlou and Farid Taheri, In Press.We Claim

1. A 3D fabric combined with lightweight metallic alloy sheets to form a new class of 3D fiber metal laminates and the method of producing this new 3D fiber metal laminate, each comprising: a resin cured 3D fabric layer(s); a resin coating residing upon the opposing surfaces of said 3D fabric layer(s); a foam used as a filler in the cavities of said 3D fabric layer(s); thin optional cloth layers laid adjacent to said 3D fabric; thin lightweight alloy sheet layers laid adjacent to said 3D fabric (or adjacent to said 3D fabric with optional layers of 2D fabrics) and an adhesive/resin to form a bond between all said layers.

2. The 3D fabric according to Claim1, wherein said core layer is comprised of said 3D-fabric, a surface coating of said resin upon opposing sides of said core, said core fabric fibers impregnated with said resin and foam injected into said fabric cavities in order to increase the structural strength and stiffness of said 3DFML, thereby forming a unique hybrid 3D fabric.

3. The 3D fabric according to Claims 1, 2 wherein said foam-filled 3D fabric may also be produced from other types of organic and inorganic fibers and hybrids of various fibers and different type foams.

6. The 3D fiber-metal laminate according to Claims 1,2,3,4,5 wherein 3D fabric cured with resin and filled with foam is combined with lightweight metallic alloy sheets to form a new class of 3D fiber metal laminates. 00 a.

7. The 3D fiber-metal laminate according to Claims 1,6 wherein said lightweight metallic alloy sheets have a preferred range in individual sheet thickness from 0.4 mm to 2 mm.

8. The 3D fiber-metal laminate according to Claim 1 wherein the preferred thickness for said individual cloth units ranges from 0.2 mm to 0.4 mm.

9. The 3D fiber-metal laminate according to Claims 1,2,3,4,5,6,7,8 wherein said lightweight alloy sheets are preferred as said outer layers of said 3D resin cured and foam-filled fabric, and as such are either bonded to said 3D fabric or to said optional other cloth layers.

10. The 3D fiber-metal laminate according to Claims 1,2,3,4,5,6,7,8,9 wherein said optional cloth layers are inserted between said 3D fabric and either or both of said lightweight alloy sheets as a reinforcing layer.

11. The 3D fiber-metal laminate according to Claims 1,2,3,4,5,6,7,8,9,10 wherein an adhesive material is disposed between said fabric core and said optional cloth layer/s to form a bond and increase the structural strength and stiffness of said laminate component.

12. The 3D fiber-metal laminate according to Claims 1,2,3,4,5,6,7,8,9,10,11 wherein said adh6sive material is disposed between said optional cloth layer and said outer thin lightweight alloy sheet layers.

13. The 3D fiber-metal laminate according to Claims 1 through 12 wherein said 3D fabric, said optional cloth layer/s, said lightweight alloy outer sheet layers, said foam filler and said adhesive material with various layers bonded together using said adhesive material.

14. The 3D fiber-metal laminate according to Claims 1 through 13, wherein said 3D fiber-metal laminate may be bonded, using said adhesive material, to another said fiber-metal laminate of similar dimensions and character, or otherwise, to form a 3D fiber metal laminate component or article, which would greatly increase the structural strength and stiffness, optimize the impact resistance and minimize delamination occurrences of the new innovative component or article.

15. The 3D fiber-metal laminate according to Claims 1 through 14 wherein said The 3D fiber-metal laminate component may be comprised of two or more of said 3D fabric components to comprise a greater thickness component or component system or greater article thickness. (1)

16. The 3D fiber-metal laminate according to Claims 1 through 19, wherein said 3D fabric laminate and said 3D fabric laminate component are subjected to vacuum pressure or other pressurization procedures to ensure optimal bond strength between various layers is achieved.

17. A method of manufacturing 3D fabric, said method comprising the steps of:
sanding the surfaces of metal alloy sheets; blowing surfaces clean and wiping with acetone; applying a liquid polymeric resin onto 3D fabric and permit to cure in oven; injecting a liquid polymer foam (or alike) into the 3D fabric's cavities and permitting it to solidify; the option of adding another layer of 3D foam-filled fabric adjacent to the said 3D fabric to increase the overall stiffness; the option of bonding layers of various types of cloth to the top and bottom of the foam injected 3D fabric layer; applying adhesive/resin to the inside faces of the outer metal alloy sheets to the mating sides of the 3D core fabric for bonding the constituents together and bonding two or more 3D fiber metal laminates together using an adhesive material to form a combination of 3D fabric metal alloy laminates or an article, and curing the adhesive layer in oven; adhering the above 3D fiber-metal laminate to another layer of 3D fiber-metal laminate to produce a component with stiffer and stronger response.

18. A method of manufacturing 3D fabric as claimed in Claim 17 that involves sanding the surfaces of metal alloy sheets, blowing surfaces clean and wiping with acetone.

19 A method of manufacturing 3D fabric as claimed in Claim 17 that involves applying a liquid polymeric resin onto 3D fabric, which in turns awakens the pillars of the fabric, transferring then from a horizontal orientation to vertical orientation, thereby separating the top and bottom 2D fabrics, creating the spacing and cavities in the 3D fabric, and permitting the combination to cure in an oven.

20. A method of manufacturing 3D fabric as claimed in Claim 17 that involves injecting a liquid polymer foam (or alike) into the 3D fiber's cavities and permitting it to solidify.

21. A method of manufacturing 3D fabric as claimed in Claim 17 that involves bonding two or more layers of the foam injected 3D fabric to form thicker, stiffer and stronger core layer for the overall fiber-metal laminate.

22. A method of manufacturing 3D fabric as claimed in Claim 17 that involves the option of bonding a layer of various types of cloth to the top and bottom or either of the foam injected 3D fabric layer.

23. A method of manufacturing 3D fabric as claimed in Claim 17 that involves applying adhesive/resin to the inside faces of the outer metal alloy sheets to the mating sides of the 3D core fabric for bonding the constituents together using an adhesive material to form a combination of 3D fabric metal alloy laminates or an article, and curing the adhesive layer in oven.

24. A method of manufacturing 3D fabric as claimed in Claim 17 that involves bonding two or more 3D fiber metal laminates together using an adhesive material to form a combination of 3D fabric metal alloy laminates or an article, and curing the adhesive layer in oven.
While particular embodiments of this invention are shown and described herein, it will be understood, of course, that the invention is not to be limited thereto since many modifications may be made, particularly by those skilled in this art, in light of this disclosure. It is contemplated therefore, by the appended claims, to cover any such modifications as fall within the true spirit and scope of this invention