Stock material or miscellaneous articles – Composite – Of polyamidoester
Patent
1997-07-14
1999-08-10
Warzel, Mark L.
Stock material or miscellaneous articles
Composite
Of polyamidoester
428911, 523142, 524590, 524871, B32B 2740, C08L 7504
Patent
active
059357134
DESCRIPTION:
BRIEF SUMMARY
This invention relates to a composite material and more particularly a composite material for use in buildings for protection against projectiles such as armour piercing bullets and the like.
There have been many proposals for protection against bullets and in particular armour piercing bullets. The conventional material for this purpose is steel, but this is expensive and not usually used in buildings. The weight of steel is such that a building in which it is used will normally need to be specially strengthened to support the load thus making the use of steel very expensive. The other conventional material is concrete. At least 14 inches of concrete is needed to stop an armour piercing bullet so that again a building would need to be specially strengthened to support the weight of material needed for effective protection.
The present invention has been made in order to deal with this problem.
According to the invention there is provided a composite material comprising an elastic resin matrix and stone aggregate distributed in the matrix.
In a preferred embodiment of the invention the aggregate is in the form of stone pebbles having an average screened size range of from about 20 mm to about 60 mm. The shape of the pebbles is not important, but rounded pebbles of the kind that occur in river beds are particularly preferred. The disposition of the pebbles in the resin matrix is preferably such that the majority of pebbles are in contact with adjacent pebbles and distributed substantially throughout the resin matrix.
The elastic resin is preferably a polyurethane resin, more preferably a polyester polyurethane, having a high elasticity i.e. elongation at breakpoint, for example an elasticity in the range 100% to 700% and more preferably between 500% and 600%.
The composite material of the invention is preferably formed by placing the stone aggregate in a mould and pouring a mixture of isocyanate prepolymer and polyol into the mould and allowing the polyurethane to cure. It is preferred that the polyurethane mix be added to the mould so as to cover the stones for example by a few millimeters so as to form a layer of polyurethane only on at least one side of the moulded product. This layer can form a so-called "spalling", or anti-spalling, layer in the product which is often desirable when constructing protection against bullets.
It is important that water should not be present during the formation of the product of the invention. To that end the stone aggregate is preferably dried by heating at a temperature up to about 80.degree. C. and then cooling to 40-45.degree. C. with appropriate ventilation. The mould also should be moisture free and may advantageously be coated with a release agent such as a wax. The mould itself may be made of any suitable material such as wood or metal.
Reference is now made to the accompanying drawing which shows by way of example a piece of composite material, partly in section. The composite material as shown comprises an elastic resin matrix 10 into which are embedded a plurality of pebbles 12. The pebbles have a generally rounded shape and are distributed throughout the resin matrix except at the sides of the product where the resin material forms a thin spalling layer 14.
Products of the invention have been found to be highly resistant to armour piercing bullets ranging from 7.62 mm to 1/2 inch. The size of the stone aggregate is desirably chosen having regard to the calibre of bullet that the material of the invention is to resist. For example smaller size stones, of the order of 20 mm average diameter are used with smaller calibre bullets such as 7.62 mm and larger size stone, of the order of 40 mm average diameter with larger bullets. The relative proportions of resin and stone in the composite material will vary to some extent depending on the size of the stones. Generally the preferred amount of resin is from 10 to 50% based on the total weight, with a particularly preferred proportion being about 25%.
If desired additives can be included in the composite material. For
REFERENCES:
patent: 4960620 (1990-10-01), House et al.
Derwent Abstract JP 62 197589 A (1987).
Hyperlast Limited
Warzel Mark L.
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