FRACTOGRAPHY OF UNFILLED AND PARTICULATE-FILLED EPOXY-RESINS

The objective of this work was to analyse the types of fracture surface morphology found in unfilled and particulate-filled epoxy resins in the light of the thermo-mechanical history of the specimen (loading rate or duration of loading, temperature, strain at break). Short-term tensile tests and long-term creep tests were conducted at four different temperatures. The fracture surface features were analysed using scanning electron and optical microscopes and, where suitable, an image analyser. In order to correlate these morphologies with certain regimes of crack velocity, fracture mechanics tests were also conducted, varying the crack speed between 10** minus **7 and 10**2m sec** minus **1. In the filled resin, the lifetime under static loading is governed by a phase of slow, sub-critical crack growth which is manifested by resin-particle debonding. Thereafter, the crack accelerates and may reach terminal velocities depending on the amount of stored elastic energy available at the moment of fracture.