Note: Descriptions are shown in the official language in which they were submitted.
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
3DFML
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
3D
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
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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
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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)
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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
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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%
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CA 3006619 2018-04-18
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
2024-
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.
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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
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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
3D
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
3D
fabric, foam, adhesive and lightweight alloy sheets will enable assembly of
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superior low velocity impact resistant laminate materials.
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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
2D
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
3D
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.
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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.
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Figure 4 is a front view of two 3D fabric laminates bonded together to form a
3D
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
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CA 3006619 2018-04-18
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
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CA 3006619 2018-04-18
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
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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
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CA 3006619 2018-04-18
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.
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CA 3006619 2018-04-18
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
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CA 3006619 2018-04-18
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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CA 3006619 2018-04-18
References:
Low-velocity Impact Response of Fiber/Magnesium FMLs with a New 3D Glass
Fabric, Zohreh Asaee, Shahin Shadlou and Farid Taheri, In Press.
CLAIMS
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.)
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