Analysis of the fracture behavior of epoxy resins under impact conditions

In this work an analysis of the fracture behavior under impact of four epox y resins was performed. The morphology of the fracture surfaces was analyze d by scanning electron microscopy and the topographic marks observed could be related to the thermal behavior of each epoxy system. The relevant prope rties that determine the thermal behavior were the thermal diffusivity, whi ch was measured by using the open photoacoustic cell technique, and the gla ss transition temperature. As the thermal diffusivity of these materials is very low, and therefore also is their heat dissipation capacity, the impac t test occurs under adiabatic conditions and a temperature increase occurs at the tip of the running cracks. Therefore, thermal blunting may occur at the crack tip and the energy absorption capacity of the resins is increased . The topographic marks observed at the fracture surface help to identify h ow efficient this mechanism is for each of the epoxy systems analyzed. (C) 2000 John Wiley & Sons, Inc.