Negative thermal expansion materials

Finite element analysis is used to explore composites of negative thermal expansion materials with positive thermal expansion materials (ZrW₂O₈ in Cu and ZrO₂ in ZrW₂O₈) and evaluate how thermal and mechanical properties, rates of cooling/heating, and geometry and packing fraction influence the overall expansion and thermal stress. During rapid temperature changes, the transient short-time thermal expansion can be considerably larger than the steady-state value. Furthermore, thermal stress in the composite can be large, especially at the interface between the materials, and can exceed the material strength.