The Temperature Dependence of Interfacial Shear Strength for Various Polymeric Matrices Reinforced with Carbon Fibers

The influence of temperature on the interfacial shear strength between epoxy thermoset matrices and surface treated, carbon AS4 as well as with surface treated and sized AS4-C carbon fibers was investigated. The thermoset matrices all consisted of DGEBA epoxy resin cured with different amine curing agents resulting in matrices with a range of behavior from brittle, elastic to ductile, plastic. For all systems, the results indicate that the interfacial shear strength (ISS) decreases with increasing temperature and as the T_g of the matrix is approached, a large corresponding decrease in the interfacial shear strength is seen. Moreover, the AS4-C (epoxy sized) system revealed a distinct decrease in interfacial shear strength at temperatures lower than the bulk matrix T_g indicating the formation of an interphase layer of composition different from the bulk matrix. Linear superposition methods were used to generate a master curve for the different matrix materials reinforced with the AS4 fibers. These results allow the prediction of ISS at any temperature.