A study of the effects of time and temperature on the fiber/matrix interface strength using the microbond test

With samples of p-aramid fibers embedded in a DGEBA-based epoxy (Tg = 110 °C), a series of experiments were conducted by the microbond method to determine the effect of testing rate and temperature on the fiber/matrix interfacial shear strength (IFSS). Microbond tests were conducted over three orders of magnitude of testing rate (0.1–100 mm min−1) and a range of temperatures (21–130 °C). While the general trend observed is that the IFSS decreased with increasing testing rate, the effect was more pronounced below Tg than near or above Tg, where the IFSS seemed to be insensitive to testing rate. We have analyzed these data by using an exponential breakdown model proposed by Zhurkov, enabling the determination of an activation energy for the failure process.