Thermal Sonic Analysis of Polymer Matrices and Composites

A commercially available sonic Pulse Propagation Meter (PPM-5R) was utilized in this study to monitor kinetic changes of matrix polymers that may be encountered in process ing operations of fiber-reinforced composites. Both thermoplastic polyetheretherketone (PEEK) and thermosetting epoxy resins and their carbon fiber composites were examined. During cure, the epoxy samples displayed obvious velocity changes at the initial softening and final cure transitions. For the neat PEEK samples, the sonic velocity decreased slowly as the temperature increased and the velocity dropped rapidly at a transition temperature of 160°C. Samples of carbon fiber-reinforced epoxy and PEEK composites were also in vestigated to examine the effect of fibers on the sonic velocity responses. The results show that the reinforcing fibers whose orientation coincides with the probe orientation have the most dampening effect on the detection of transitions using the sonic technique. Overall, the sonic technique for process monitoring is discussed in this paper.