US Patent 7662457 Wood composite material containing strands of differing densities

Disclosed is a wood composite material comprising: wood strands disposed in surface layers and one or more core layers, whereby an intermediate density divides the wood strands so that the two surface layers of strands are more dense than the intermediate density, and the one or more core layers of the strands are less dense than the intermediate density, and wherein the core layer contains at least about 70 wt % of the strands that are less dense than the intermediate density; and the surface layers contain at least about 70 wt % of the strands that are more dense than the intermediate density.