Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
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PROTECTIVE MATERIAL
FIELD OF THE INVENTION
This invention relates to a protective material.
BACKGROUND OF THE INVENTION
It is known to use personal body armour to give protection
against a wide variety of threats. This armour typically comprises a pack
containing layers of woven aramid fibre.
In order to provide the capability to resist multiple hits from
projectiles it is usual to stitch or quilt the layers together; this helps to
prevent "bunching", which causes the layers to bunch up together, and
progressively reduces the protection a*er each hit.
It is also known to provide additional material to reduce the
trauma effect caused to the wearer by the impact of the projectile. The
additional material may comprise, for example, one or more layers of
plastic or rubber foam; one or more polyolefin sheets; or one or more
packs of feathers.
When protection from knife impact is also required it is usual
to add a still further layer, which comprises, for example, metal meshes;
lightweight metal panels; or overlapping medallions of lightweight metal.
It will be appreciated that each protective layer adds to the
thickness and weight of the armour, thereby reducing its wearability.
It is an object of the present invention to provide an improved
protective material.
SUMMARY OF THE INVENTION
According to one aspect of the present invention there is
provided a protective material having at least one flexible layer
comprising a plurality of fibres capable of resisting penetration by a
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bullet, and a support material, said fibres being at least partially
embedded within the support material to restrict relative movement of the
fibres therein.
It is a particular feature of this invention to provide more than
one of said flexible layers. The protective material most preferably
comprises a plurality of thin laminates, each laminate comprising one of
the flexible layers. It is particularly preferred that the laminates are not
adhered, or otherwise bonded, together. We prefer that the laminates are
loosely bound together so that they can move relative to one another.
DETAILED DESCRIPTION OF THE INVENTION
.Advantageously the support material is a resin, more
preferably a synthetic resin, and most preferably a thermosetting resin.
The precise resin used depends upon the final application of the material:
an epoxy-based resin, a phenolic-based resin or a polyester-based resin is
preferred. It is also preferred that the support material has sufficient
rigidity to enable the or each flexible layer to support its own weight.
The fibres are typically of the type that have a high tensile
strength and a high stretch resistance. The fibres may comprise high
strength polyethylene fibres, glass fibres, or carbon fibres. In the
preferred embodiment the fibres comprise aramid fibres, particularly
fibres of poly(p-phenylene terephthalamide). When aramid fibres are
used, they may, for example, comprise the fibres sold under the trade
names KEVLAR or TWARON.
In one embodiment, the fibres are woven to form a fabric,
prior to being embedded in the support. In another embodiment, the fibres
are arranged in a unidirectional manner, i.e., they are not woven.
Preferably the protective material contains 20-50 wt% of the
support material, most preferably 33 wt%.
It is preferred that the fibres are substantially entirely
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embedded in the support material, because this provides the best
resistance to penetration by a knife or similar object.
There are a number of parameters of the protective material
which depend upon the use to which it will be put, and also on the type of
fibres and support material used. These parameters include the number of
flexible layers, the thickness of each flexible layer, and the denier of the
fibres. Typically, there will be between 5 and 50 layers, each having a
thickness between 0.2mm and 0.5mm, with the fibres having a denier
between 400 and 1500.
The most preferred fibres are available from Du Pont under
the registered trade name KEVLAR 129 (or KEVLAR HT). Using these
fibres, together with a resin comprising a blend of bisphenol A and
bisphenol F, the denier of the fibres is most preferably 840, the thickness
of each layer is preferably 0.25mm and the number of layers is preferably
26. This will provide a level of protection that can prevent penetration by
hand gun bullets, and can provide adequate protection against trauma; it
will also provide protection against a knife strike having an energy of 42
Joules, or more. The material is capable of meeting applicable Standards
set by the British Home Office.
In order to provide sufficient protection against high velocity
bullets the protective material may include at least one layer of ceramic
plates, such as alumina plates. It will be appreciated that other materials,
known to those skilled in the art, may be used to provide protection
against high velocity bullets.
The protective material according to the invention is
particularly useful as personal body armour. For example, it can be
provided in the form of, or as part of, a vest or jacket for providing body
protection to the front and/or the back; it may be provided in the form of,
or as part of, any other garment to protect any other part of the body, for
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example the arms or the legs. The protective material may be provided in
the form of, or as part of, headwear, such as a helmet; or it may be
provided in the form of, or as part of, footwear, such as boots. The
protective material may be provided in the form of, or as part of, a hand-
held shield.
The protective material may be provided in the form of a
pack that can be removably secured to a garment. It may be incorporated
into an existing protective garment by mixing with or adding to protective
layers already in the garment - this will enhance the performance of the
protective layers already present.
The protective material according to the invention may
instead be used as armour for vehicles, ships, aeroplanes or buildings.
It is possible to protect against a wide variety of ballistic
threats with the protective material according to the invention. The
material can also provide adequate protection against trauma, without the
need to use any additional layer of a different material. The material is
also capable of preventing penetration by a knife or other sharp
instrument.
The material is resistant to the problem of bunching,
discussed above, due to the ability of each layer to support its own weight,
so it is not necessary to stitch or quilt together multiple flexible layers.
According to another aspect of the invention there is provided
a composite material comprising aramid fibres treated with a resin.
Advantageously the aramid fibres are poly(p-phenylene
terephthalamide). The resin is preferably a synthetic resin, and is most
preferably a thermosetting resin: epoxy-based resins and phenolic-based
resins are particularly preferred.
The resin can provide a matrix, into which the fibres are
embedded, in order to resist relative movement of the fibres within the
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resin; the resin may be impregnated into the fibres.
The composite material is preferably flexible, but sufficiently
stiff to support its own weight.
The composite material is particularly useful when provided
in sheet form, when it may be used as a protective material as described
above.
In one embodiment, the protective material can be made by
pre-impregnating the fibres with a resin, then subsequently curing the
resin by heat and pressure (typically from 100 to 150 degrees C and 50 to
150 psi [345 to 1035 KPa]). The pre-impregnated fibres may be stored
and/or transported, preferably in roll form, before they are finally cured.
In another embodiment, the protective material may be made
by impregnating the fibres with a resin, followed by curing shortly
thereafter. In this embodiment a low viscosity epoxy resin is preferred,
such as a resin manufactured from epicholorohydrin with a blend of
bisphenol A and bisphenol F (this is available from ASTOR STAG as
product type 629), and a suitable curing agent. The curing agent may be a
polyalkylamine; one example of a suitable curing agent is available from
ASTOR STAG as product type RS 4025. An entire roll, or part of a roll,
of the fibres may be dipped in the resin to coat either the entire roll or part
of the roll. The resin can be cured at ambient temperature under a
pressure of 10 to 20 psi (69 to 138 KPa).
In both embodiments, the impregnated material can be cut
into sheets either before or a*er curing. When the material is cut into
sheets before curing, then between 5 and 50 sheets may be placed on top
of one another with a release film between each layer. The release film
may be, for example, mylar, a polyolefin film, or a silicone-coated paper.
The multiple sheets can then be cured; after curing the sheets are
separated, and the release film is either discarded or re-used.
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One or more of the layers may then be used to form the
protective material described above. The material may then be used on its
own, or may be added to standard ballistic fabrics in order to improve the
performance thereof.
The impregnated material can be shaped before it is cured, for
example in a mould. If desired, the impregnated material can be cured in
the mould. One reason to shape the material is to provide a shape suitable
to be worn by a woman.
Whilst certain embodiments of the invention have been
described above it will be appreciated that modifications could be made to
the invention, within the spirit and scope of the appended claims.
