Composite material with a core and an adhering coating united thereto

A composite material is formed with a porous core obtained by randomly folding or crumpling metal foils or filaments and has a coating adapted to strengthen the final product, of an adhering synthetic resinous material. Preferably, the core material is made more dense at the surface than at the interior as by hammering, pressing, striking, rolling, etc. To permit greater penetration of the resinous coating into the core, the core may be slit, punched or bored. The surface of the coating material may be further treated by fillers, painting, coating, vapor deposition, etc.

The invention concerns a composite material with a core from porous 
material of low density and strength and a coating covering the whole or 
part of the surface which is adhesively bound to the core and of a 
material of higher density and strength than the core material. 
Composite materials are useful in many technical areas. They consist, as a 
rule, of a core of a relatively light, often also sound or heat insulating 
material, which is fixed to one or more covering layers of material of 
higher strength, for example, by adhering with adhesive. While the core 
material is frequently of a foamy material, the coatings can comprise any 
material, for example, wood, wood material, metal, stone, or synthetic 
stone or even plastic material. 
The important lightness of the core materials necessary for many uses is 
generally obtained by employing materials with air or gas pores, in the 
core of which the necessary strength for this material is attained through 
the incoherent blending walls of the pores. This material is, however, not 
suited for all applications, because it often succumbs to rotting or 
corrosion so that when the core material has not sufficient stability or 
durability, the whole material cannot be suitably applied. 
A problem of the invention is to provide a composite material of the type 
described above which has the advantageous properties of metals with 
respect to rotting and corrosion and therefore is safer against rotting 
than the known composite material and which, furthermore, is simpler to 
manufacture and also possesses lightness and high strength. 
The invention solves this problem by a composite material of the type 
described above, wherein the core consists of an uncohered narrow, folded, 
or crumpled metal foil or filament, and the layers comprise a synthetic 
adhesive resin, e.g., expoxy resin. 
Thus, the material of the core can be more severely consolidated in the 
area of its surface, e.g. by hammering, striking, rolling or the like, 
than in its interior region. The core can be provided with punctures, 
cuts, bores or the like, into which the synthetic adhesive penetrates. 
The binding material can be built up as a polylayered material, whereby 
intermediate layers of synthetic adhesive resin are suitably arranged 
between the individual layers of cores. 
The surface layer can be provided with an altered coating, e.g. through 
fillers, polishing, spraying, steaming or the like. 
The composite material can also consist of a plurality of similar or 
essentially similar developed individual elements which are combined for a 
greater surface or greater volume structure and which are connected to one 
another through adhesive. Thus, individual elements may be joined flush 
with one another or be notched with one another. They can also be provided 
with tongue and grooves, pins, dowels, tension tubes or the like. 
The material of the invention is simple and easy to manufacture in any 
desired dimension. Through the random folding or crumpling of metal foils 
or filaments, a cellular structure with three dimensional reinforcements 
is attained. Depending on the strength of the compression of the crumpled 
foil, in any given case, the foil in the surface regions can be stronger 
than in the inner regions, and the size of the cells and accordingly the 
strength of the core material can be influenced. 
Of especial advantage is that the material of the core has the inherent 
possibility for plastic forming and the performance of the work of form 
change. Thus, the new compact material can, for example, provide a bumper 
for power vehicles which has the normal requirements for high strength, 
but, however, in the case of a collision if the layered material is 
destroyed it annuls the kinetic energy through fortified compression. The 
material operates similarly on being shot at, where the multilayered 
material annuls kinetic energy of a shot through deformation and the shot 
is broken down in the layers or so strongly retarded that it can perform 
no more damage if it penetrates the layers. 
The folding or crumpling can be accomplished by any known working process. 
At the same time, the shape of the core body can accompany the process of 
folding or crumpling. Thus, it is possible without further details, for 
example, to press the starting material, e.g., the foil, in a fixed formed 
cavity in order to produce a certain shape. In this way, a cellular 
element can be formed which has either quadratic with smooth outer faces 
or whose outer faces are so formed that adjacent individual elements can 
enter into key form combination. 
The core part formed as disclosed above, is then coated on the outer faces 
with a resinous adhesive, e.g. of an epoxy resin basis, which enters into 
the material of the core for inner binding and which yields a sandwich 
structure of necessary rigid covering layer. Through the cellular 
structure of the core material, there results a good bonding of the 
coating material with the core material. A further strengthening of the 
material can be attained by a puncturing, a slitting of the core which 
penetrated either only, to the depth of the metal foil or through the 
whole core and into which the artificial resin adhesive applied to the 
surface can penetrate so that the whole work piece is intersected. 
The artificial resin used for increasing the strength and stiffness of the 
outer surface can, however, also be employed for bonding several like or 
similarly formed individual elements together. Thus, there is the ability 
to build up systematically large formed members of any shape from small 
and smallest building components. These members, which can be of two or 
three dimensional form, can be treated at the surface in any way. The 
members with the hardened artificial resin adhesive coating can be treated 
at the surface by grinding, by filling in with a spatula, by lacquers, or 
by coating with other materials. 
In a similar way, the new material can also be combined with other 
materials, e.g. wood, natural or artificial stone, metals, plastic or the 
like. 
The composite material of the invention can be installed for many different 
functions of different technical domain. Through the choice of different 
metals, e.g. pure aluminum, copper, steel, gold, alloys thereof, etc., as 
also high quality adhesive, through structure and size of the structural 
elements, the manufactured elements can be made with a wide variety of 
properties in tensile and bending strength, corrosion resistance, density, 
shock absorption, as well as thermal-physical and chemical behavior. the 
use of the new composite materials extends from power vehicles, airplanes 
and ship construction and furniture industries up to dental techniques 
(filling of tooth cavities) and armament industries. 
The invention will now be further explained with the aid of the 
accompanying drawing showing non-limiting embodiments thereof,

The block 1 consists of a core 2 of crumpled metal foil, e.g. aluminum 
foil. The thickness of the foil is about 1/10 to 1/100 mm. The compression 
of the foil material to form the total core varies; the outer regions 2a 
are more severely compressed than the inner regions 2b. The stronger 
compression in the region 2a can be obtained, for example, by hammering or 
rolling. 
The core 2 is covered on all sides with a coating 3 of an adherent 
synthetic resin, e.g., having an epoxy resin basis. The thickness of the 
coating which enters into the surface of the core 2 to form an intimate 
bond, amounts to about 1/10 to 1 mm. The thickness of the block itself in 
the form shown, can be about 1 to 10 mm; its breadth can be about double 
the thickness and the length can be any length desired. The new composite 
material can employ foils of such length as to manufacture rods therefrom 
(FIG. 2). The coating 3 of adhesive synthetic resin serves in the first 
place to stiffen and strengthen the core material, but this coating, in 
its fresh state, can also be employed to unite a plurality of such blocks 
1 or rods 4 together to form a larger workpiece. 
In order to obtain good penetration of the respective cores by the adhesive 
synthetic resin, the core can be provided with punctures, slits or bores. 
In the example of the rod 4 of FIG. 2, the various sides of the core 5 are 
provided with punctures 6, in which the coating material 7 penetrates. In 
a similar way the core can be provided with slits or bore holes which are 
penetrated by the resin.