Formable light weight composites

A method for making a light weight composite comprising:

• (i) providing a roll of a first metallic layer, wherein the first metallic layer is a foil;
• (ii) providing a roll of a second metallic layer, wherein the second metallic layer is a foil;
• and
• (iii) providing at least one sheet of a polymeric core layer, the polymeric core layer including greater than 40 volume percent of a thermoplastic polymer, based on the total volume of the polymeric core layer, and from about 3 volume percent to 25 volume percent metal fibers based on the total volume of the polymeric core layer, wherein the metal fibers have an average length from 100 μm to 8 mm, and the thermoplastic polymer includes a polyethylene copolymer consisting of one or more α-olefins and optionally one or more additives wherein the thermoplastic polymer forms a polymeric matrix and the metal fibers are dispersed in the polymeric matrix:
• (iv) disposing the polymeric core layer between the first layer and the second layer;
• (v) heating the metallic layers to a temperature greater than about 90° C.;
• (vi) heating at least a portion of the polymeric core layer to a temperature greater than Tmin, wherein Tmin is the higher of the maximum melting temperature of the thermoplastic polymer of the polymeric core layer, as measured by differential scanning calorimetry at a heating rate of 10° C./min, and the maximum glass transition temperature of the thermoplastic polymer of the polymeric core material;
• (vii) applying a pressure to the metallic layers and the polymeric core layer so that a sandwich composite is formed, wherein the concentration of pores and voids in the polymeric core layer is from 0 to about 10 volume %, based on the total volume of the polymeric core layer;
• and
• (viii) cooling the composite material below the melting temperature of the thermoplastic polymer of the polymeric core layer;
• wherein the process is free of a step of heating the composite material to a temperature at which the metal fibers fuse together;
• wherein the polyethylene copolymer includes at least about 80 weight % ethylene, the volume ratio of the thermoplastic polymer to the metal fibers is greater than about 3:1, and the thermoplastic polymer has a number average molecular weight greater than about 20,000;
• wherein the thermoplastic polymer optionally further comprises a grafted polymer including a maleic anhydride grafted polyolefin,
• wherein the concentration of any grafted polymer in the polymeric core layer is up to about 10 wt %, based on the total weight of the polymeric core layer;
• and
• wherein the resulting composite material may be plastically deformed at strain rates greater than about 0,1 s−1.