Composite materials of controlled thermal expansion

Properly designed composite materials can produce thermal expansion coefficients lying well outside the range shown by homogeneous materials both in a single direction and in a plane. Much lower negative values may be produced compared with single materials as well as larger positive values. Such extreme values may be coupled with a choice of other mechanical properties, e.g., Youngs modulus or breaking strength or toughness. In this paper, we demonstrate how to obtain negative values of the expansivity.