ABSTRACT
The effects of interphase elastic modulus, glass transition temperature, and thickness on interfacial shear strength were investigated both experimentally and theoretically. Single fiber fragmentation tests were performed over a range of temperatures on samples with tailored interphases. Three different types of interphases were investigated: high modulus/high glass transition temperature, low modulus/low glass transition temperature and uncoated (no tailored interphase). A reduction in interfacial shear strength with temperature was observed for all three types of samples tested. The magnitude of this decrease was found to correlate with the glass transition temperature of the interphase. The low Tg interphase samples showed large reductions in IFSS, while samples with a higher Tg coating showed only a small decrease. A three-phase, axisymmetric elasticity solution was developed to predict the sensitivity of the stress state to the interphase material properties and temperatures used in the experimental studies. Predictions which incorporated the change in modulus of both the matrix and interphase with temperature were in good agreement with the experimental trends. Both the theoretical and experimental results supported the existence of an interphase with reduced glass transition in the uncoated samples.
