Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
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COMPOSITE MATERIALS FOR SPORTS ARTICLES AND METHOD OF
MANUFACTURING THE COMPOSITE MATERIALS
The present invention relates to a composite material, sports articles
produced from
the composite material and a method for their manufacture. More specifically,
the
invention relates to a composite material which can be used to, for example,
manufacture sports articles such as skis, snow boards, skate boards, surf
boards, and
wave boards and other articles of drastic mechanical properties.
BACKGROUND OF THE INVENTION
The invention relates to composite materials, which are materials which have a
thermohardening polymer matrix and a fibrous reinforcement, and possibly
granular fillers and additives. The polymer matrix plays the role of a binder
for the
fibers of the reinforcement. It distributes and ensures the transmission of
the forces
to the fibers. The fibrous reinforcement, oriented (woven or non-woven) or
random
(non-woven) provides the finished composite with the necessary mechanical
properties of strength and rigidity. These composites are used as raw material
in the
automotive industry, shipbuilding, aircraft industry, textile industry, sports
article
industry
The composites can be in the form of sandwich or laminated constructions,
formed
by a plurality of fibrous layers embedded in the matrix. The polymer matrix
may be
selected from among thermohardening or catalysed resins; examples are
phenolic,
polyester; vinylester; epoxide, polyamide, polycarbonate, polyacetal, vinyl
styrenic
esters. These "sandwich" or laminated composite constructions have the
characteristic of being relatively lightweight and extremely rigid. This
stiffness is
such that mechanical deformability is very much reduced and mechanical
properties
generally enhanced.
U.S. Patent No. 3,873,168 describes an article made of composite laminate
having a
body constituted by a polyamide cross-linkable resin and reinforced by a glass
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fiber. This body is inserted between two composite outer bearing portions
whose
matrix is also made of cross-linkable polyamide resin, and whose fibrous
reinforcement is formed by a graphite fiber. The composite laminate according
to
U.S. Patent No. 3,873,168 has the disadvantage of being too rigid and
relatively
expensive.
U.S. Patent No. 3,779,851 discloses a composite laminate constituted of a
plurality
of graphite fiber sheets impregnated with epoxy resin. This laminate is
presented as
having a very high mechanical strength to weight ratio, as well as very low
thermal
expansion properties. Such specifications are desired for applications of
these
composite laminates in the manufacture of optical instruments (mirror). These
are
also extremely rigid composite laminates. This composite laminate is too stiff
to be
used as raw material in the manufacture of sports articles, such as skis,
skate boards
or snow boards for example, where a certain deformability or bending ability
in
both the longitudinal and latitudinal direction is needed. In addition, the
fibrous
reinforcement is exclusively made of carbon fibers. This method of
construction,
while suitable for use in the hi-tech areas of aero space, is too costly to be
applied
to the manufacture of sports articles.
US Patent No. 5,716,562 discloses a board made of a uniform composite mixture
of carbon fibre and a thermohardening resin. However, this is a monologue
construction, in that it is uniform throughout (i.e. no core). Moreover, this
construction does not recognize the need for different mechanical properties
through the laminate, wherein the core should be rigid, and outer layers being
provided with more flexibility.
A review of the state of the art shows that the manufacturers of sports
articles are
always looking for a materials having the mechanical properties of the
composites
in terms of maximum stiffness and minimum deformability, combined with a
vibration dampening capacity, which is inexpensive and lightweight. These
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manufacturers also expect such a raw material to be easily industrially
workable
and shapable and, finally, to preserve its mechanical properties over a long
period
of time.
SUMMARY OF INVENTION
The object of the present invention is to provide a new composite structure
for
making articles of manufacture, in particular sports articles, which are cost
effective, lightweight and extremely rigid. This stiffness is such that
mechanical
deformability is very much reduced and mechanical properties generally
enhanced.
This object, among others, is achieved by the present invention, which relates
primarily to a composite laminate manufactured from multiple layers of
composite materials made up of sheets of fabric, woven or non woven, embedded
in a resin, which when catalysed and or heated becomes a hard continuous
matrix
bonding the fibres together. The laminated material may be consistent in
composition through the article or contain a core material of substantially
more
rigid fibres, manufactured from high performance micro fibres, sandwiched
between outer layers of more flexible fibre mats combinations.
According to one aspect of the present invention, there is provided a
composite
laminate for forming articles therefrom, the composite laminate being
comprised
of a plurality of layers of impregnated resin composite materials having
fibres
therein, the layers being arranged in a sandwich construction and super
imposed
on each other.
According to a further aspect of the present invention, there is provided a
composite laminate for forming articles therefrom, the composite laminate
being
comprised of a plurality of layers of impregnated resin composite materials
having fibres therein, the layers being folded around each other so as to form
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outer layers of a sandwich structure; and a core material comprised of stiffer
more
rigid impregnated fibres inserted between the plurality of layers of pre-
impregnated resin composite materials.
According to a further aspect of the present invention, there is provided a
use of
the laminate according to the present invention for manufacturing sports
articles.
According to another aspect of the present invention, there is provided a
composite board having a deck formed from the composite laminate according to
the present invention.
According to yet another aspect of the present invention, there is provided a
method of manufacturing a composite laminate, the method comprising
assembling a plurality of layers of composite materials having fibres therein
into
a mould, the layers being arranged in a sandwich construction and super
imposed
on each other; applying a vacuum to the mould; injecting a resin and catalyst
mix
into the mould so as to evenly saturate, by means of the vacuum being applied
to
the mould, the layers of composite materials with the resin and catalyst mix;
and
subjecting the layers of composite materials to heat and pressure until the
resin
and catalyst mix has cured and imbedded the fibres of the composite materials
together.
According to yet another aspect of the present invention, there is provided a
method of manufacturing a composite laminate, wherein successive layers of
fibre materials, woven or non woven mats, which are directionally oriented or
randomly distributed, are manually coated with a polymer matrix, assembled and
superimposed on each other in a mould and subjected to heat and pressure until
the polymer matrix has cured and imbedded the fibres.
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A further aspect of the present invention provides for the rapid removal of
the
article from the mould after curing, in that the mould is split evenly between
top
and bottom sections and the article is ejected cleanly after curing, reducing
the
level of secondary manufacturing necessary to produce a finished article.
Yet another aspect of the present invention provides for a method of
manufacturing a composite laminate, the method comprising assembling a
plurality of layers of composite materials having fibres therein into a mould,
the
layers being arranged in a sandwich construction and super imposed on each
other; applying a vacuum to the mould; injecting a resin and catalyst mix into
the
mould so as to evenly saturate the layers of composite materials with the
resin
and catalyst mix; and subjecting the layers of composite materials to heat and
pressure until the resin and catalyst mix has cured and imbedded the fibres of
the
composite materials together.
The advantage of the present invention is that it provides an improved
composite
material for making articles of manufacture, in particular sports articles,
which
are inexpensive, lightweight. and extremely rigid. This stiffness is such that
mechanical deformability is very much reduced and mechanical properties
generally enhanced.
BRIEF DESCRIPTION OF THE DRAWINGS
A preferred embodiment of the present invention is described below with
reference
to the accompanying drawings, in which:
Figure I illustrates a cross-section of the laminate according to the present
invention, and which shows the core structure sandwiched between multiple
layers
of composite material;
Figure 2 illustrates a cross-sectional view of the continuous laminate
according to
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the present invention;
Figure 3 illustrates a crossectional view of the laminate either with a core
structure
or with a continuous construction, where the layers of fibre material are
folded
around each other, to produce a reinforced profiled edge to the article; and
Figure 4 illustrates the unique design of the mould, to assist removal of the
article
after curing and reduce the level of secondary manufacturing required for a
finished
article.
DESCRIPTION OF THE PREFERRED EMBODIMENT
FIG. I shows the composite laminate 1 according to the invention. The latter
is
constituted of a structure having a core or central member 2 inserted or
sandwiched
between multiple layers 3 and 4. This core 2 is of a construction of more
rigid fibre
mat combinations and layers 3 and 4, which can be, in an alternative
embodiment,
pre-impregnated with resin or resin catalyst mix. The outer layers are,
preferably
however, comprised of non resin impregnated fabrics, which are then later
saturated
with a resin and catalyst mix under vacuum in a mould, as hereinafter
described.
The material comprising the layers is preferably the same for all of layers 3
& 4
and reinforced by fibres (fibrous materials). The fibrous material of the
layers 3 and
4 is constituted from high performance fibres, which offer a higher level of
flexiblilty and toughness than those comprising the central core, such as
glass,
Kevlar TM, Vectran TM, woven or non woven, and deliberately oriented in
various
directions or randomly arranged..
Advantageously, the fibrous material of the layers is in the form of: I.)
linear
continuous assemblies of (micro)fibres combined in strands or wicks of various
shapes (glass strands, single strands, cabled strands, wicks, woven mat or non
woven mat); ii.) non-linear strands (discontinuous), mats, chopped strand mat
or
continuous strand mat, surface mat, needled mat.
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According to one arrangement of the invention, the layers 3 and 4 are each
constituted by a plurality of layers; in this case 4 for the layers 3 and 4,
respectively). In practice, the layer(s) 3 and 4 are obtained by superimposing
the
layers of fibrous and/or composite materials. Thus, the composite laminate 1
according to the present invention has a core structure and one or several
layers
forming the outer layers. These outer layers are formed by plies of fibres
that are
woven or unwoven, oriented or non-oriented, and which can be, in an
alternative
embodiment, pre-impregnated with resin or resin catalyst mix. The outer layers
are,
preferably, non resin impregnated fabrics, which are then later saturated with
a
resin and catalyst mix under vacuum in a mould, as hereinafter described.
In the case of the pre- impregnated composites the laminated sheet is
preferably
manufactured by assembling the layers in a jig and curing in a mould under low
pressure / hot pressing or moderate pressure / hot pressing, the preferred
method
being moderate pressure / hot pressing.
In the case of non impregnated fabric the preferred method is to assemble the
layers
of fibrous and/or composite materials in a receiving mold under vacuum, then
the
fabric is saturated with a resin and catalyst mix. As a result of the vacuum
process,
the resin, once inserted into the mould, permeates throughout the fibrous
and/or
composite materials in the mold. The resulting saturated fabric is then cured
in a
heated mould under low pressure high temperature or moderate pressure high
temperature conditions. One of the problems with assembling pre-impregnated
fabrics in a mold is that such pre-impregnated material may have too much
resin in
certain locations, so that, when superimposed and cured in the mold, bubbling
or
imperfections may occur in the laminate, when the resin is cured. By
assembling
the layers of fibrous and/or composite materials in a receiving mold under
vacuum,
then saturating the fibrous and/or composite materials with a resin and
catalyst mix,
the resin, under the vacuum process, permeates the layers of fibrous and/or
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composite materials evenly.
In a preferred embodiment, between 1 and 6 layers of rigid fibre materials can
form
the core of the sandwich, with the outer layers, between 4 to 12, being formed
of
more flexible fibre combinations. It will also be apparent that orienting such
fibrous
material or reinforcing elements in different directions, will impart
reinforcing in
several directions i.e. across the directions of the fibres, and equalize the
mechanical properties in all directions. For example, aligning these in only
one
direction would provide a laminate very strong across that direction, but
rather
weak along it. In a preferred embodiment of the present invention, the
reinforcing
core is manufactured from a group of high performance fibres consisting of
carbon
fibres, graphite fibres or combinations of carbon and graphite fibres.
In a preferred embodiment, a total thickness of the finished composite
laminate
according to the present invention is between 4 mm and 30 mm. For evident
reasons of ease of manufacturing, the embodiments in which the polymer matrix
of
the core 2 and of the layers 3 and 4 is constituted by a single product are
preferred.
FIG. 2, illustrates the laminate consisting of 11 layers, which may be all of
the same
fibre or of mixtures of fibres. The arrangement of fibre mats vertically
through the
article will be uniform. The fibres mats may be pre- impregnated with resin
or,
preferably, consist of non impregnated mat, then impregnated with resin by
vacuum.
In an alternative embodiment, chopped fibres constructions could also be used,
in
which case resin transfer techniques are the preferred method of manufacture.
Fig 3 shows composite laminate 3 according to the invention, where successive
layers of non impregnated fibre materials, woven or non woven, may be folded
around each other or around a reinforcing core and assembled in a mould. A
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vacuum is drawn on the mould and the construction saturated with a catalysed
resin, which is injected into the mould. The resulting saturated material can
then be
subjected to heat and pressure and cured in a heated mould under medium
pressure
high temperature conditions, as hereinafter described.
Alternatively pre-impregnated fibres may be folded around each other or around
a
reinforcing core, and placed in a mould. The resulting construction can be
subjected
to heat and pressure and cured in the mould under high temperature medium
pressure conditions.
In a preferred embodiment, between 1 and 6 layers of rigid fibre materials can
form
the core of the sandwich, with the outer layers, between 4 to 12, being formed
of
more flexible fibre combinations. It will also be apparent that orienting such
fibrous
material or reinforcing elements in different directions, will impart
reinforcing in
several directions ie. across the directions of the fibres, and equalize the
mechanical
properties in all directions. For example, aligning these in only one
direction would
provide a laminate very strong across that direction, but rather weak along
it. In a
preferred embodiment of the present invention, the reinforcing core is
manufactured from a group of high performance fibres consisting of carbon
fibres,
graphite fibres and combinations of glass and carbon fibres.
In manufacturing the present invention, in a preferred embodiment, the stacked
layers of the composite materials are placed into the mold at 200 F 90C for
between 2 to 3 minutes (after the resin has been injected therein, if non-
impregnated mats are used), and pressure is then exerted in an amount of 150
psi
(10 Kg / sq cm), then, increasing the heat applied to 135 C 270 F for between
6 to
8 minutes and pressure exerted in an amount between 400-500 psi. (28 - 36 Kg /
sq
cm). Finally, the pressure exerted is increased to 600 psi (40 Kg / sq cm) for
5
minutes. The finished composite laminate is then extracted from the mold, is
allowed to cool, and the finishing operations, such as trimming, are
undertaken.
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Generally speaking however, in alternative embodiments, the manufacture of the
present invention could be obtained applying heat at anywhere from 90F to 275F
and pressure from 100 to 1,000 psi, ( 6 kg / sq cm to 60 Kg / sq cm) over time
periods of 8-30 minutes. In any event, the person with ordinary skill in the
art is
capable of adjusting these parameters depending on the types of materials
used.
Fig 4 illustrates the preferred profile and design of the mould. To facilitate
removal
of the composite sandwich from the curing mold it has been found advantageous
to
profile the corners of the mould and to design the mould to split into two
equal
sections, top and bottom. This arrangement has been found to allow; quick
access to
the cured article, rapid removal without any damage or distortion and minimum
secondary finishing or machining.
Of course, the finished composite laminate of the present invention thus
manufactured is lightweight, economical, and has the expected mechanical
properties in terms of longitudinal bending and transverse stiffness,
vibration
damping, rotational stiffness and can be machined, using a range of wood
working
techniques well known to those skilled in the art, such as, trimming sanding,
buffing, polishing and planning.
Further, the present invention can be used for manufacturing sports articles,
such
as, but not limited to skis, snowboards, skateboards and waveboards.
The present invention has been described herein with regard to preferred
embodiments. However, it will be obvious to persons skilled in the art that a
number of variations and modifications can be made without departing from the
scope of the invention as described herein.
