Examination of the processes of deformation and fracture in a silica-filled epoxy resin

A series of short-term fracture tests have been undertaken on a silica-filled epoxy resin in order to examine the processes of damage initiation, development and fracture in a particulatefilled polymer. Several different types of inelastic deformation and fracture mechanisms were observed within the volume of the material. These included localized shear yielding, particlematrix debonding and micro-cracking. The relative amount of each of these was found to depend upon the test rate and temperature. At low temperatures and high rates of loading, failure was associated with one single debonding event whereas at high temperatures and low rates, debonding and yielding were found to be extensive throughout the volume of the test specimens. A detailed examination of the fractured specimens identified several distinct regions on the fracture surface. Surrounding the defect the particles were often debonded from the matrix suggesting that the crack had propagated in a sub-critical manner. Beyond this zone was a smooth zone corresponding to the region over which the crack was accelerating unstably. The smooth zone then developed into a rough three-dimensional zone in which the crack was propagating at its maximum velocity. The size of each of these zones was found to vary considerably with test temperature and cross-head speed.