Temperature effects on the strength and crushing behavior of carbon fiber composite truss sandwich cores

The effects of temperature on the mechanical behaviors of composite rods and carbon fiber composite truss sandwich cores were investigated in this paper. Strength and stiffness of composite rods in fiber-aligned direction were measured in the range of −60 °C to 260 °C and characterized as functions of temperature. The research on out-of-plane compressive properties of sandwich panels with truss cores for temperature variation indicated that strength and failure modes of sandwich panels were significantly dependent on temperature. The stiffness and strength of composite rods and sandwich panels decreased progressively as temperature increased. The decreasing of stiffness and strength at high temperature was mainly attributed to softening of the polymer matrix. The increasing of stiffness and strength at cryogenic temperature was due to reduced mobility of the polymer chains within the resin matrix and the more closely compacted molecules of resin matrix. In order to provide insight into the effect of temperature on failure mechanism, the interface between fiber and matrix was examined using scanning electron microscope, and good interfacial bonding condition was observed at cryogenic temperature. The stiffness and strength of sandwich panels at different temperatures were predicted with proposed method and compared with measured results. Good agreement was observed between the measured values and predictions.