ABSTRACT
The low-temperature thermal expansion of polymer composites has been widely studied due to its importance for materials used in structural applications. Thermochemical expansion arises primarily from the thermally induced chemical degradation of the polymer matrix. The conversion of the polymer to gaseous products combined with the limited permeability of the material results in the rapid buildup of gases within the material, extremely high internal pressures, and thus expansion of the material. Thermochemical expansion is quite important for polymer composites used as ablative thermal protection systems for both military and aerospace applications. The expansion characteristics of polymer composites utilized in high-temperature applications are of particular importance. The response of a polymer composite to an applied heat flux may be visualized as occurring in several distinct temperature regions, each of which is characterized by certain controlling physical and/or chemical processes.
