Instrumented impact behavior of particulate-filled composites

A study of the influence of calcium carbonate on impact energy of CaCO3/high-density polyethylene composites was conducted. Composites with calcium carbonate in the range of 0-40% were produced by twin-screw extrusion followed by compression molding. Notched Izod impact tests of composites were carried out using an instrumented impact tester. It was found that increasing the calcium carbonate content decreased impact resistance. Transition in total impact energy with filler content was observed at 20% filler volume fraction, similar to propagation energy. In the case of the initiation energy, the transition was found at a different level, 10% filler volume fraction. The impact fracture process of polyethylene was seen to be initiated by crazing, followed by brittle failure, whereas composites were initiated by microvoid nucleation from interfacial failure between the filler and matrix and were propagated via microvoid coalescence.