Low-velocity Impact Characterization of Glass, Carbon and Kevlar Composites Using Repeated Drop Tests

Abstract

Low-velocity (≅ 1.2-2.4 m/s) repeated drop weight impact tests were carried out on advanced composites (glass, carbon, kevlar in epoxy matrix - LY 556, HT 972) using an instrumented impact test machine (DYNATUP 8250). The incident energies ranged from 3.5 to 15 J (constant impactor mass 5.42 kg). Number of drops to failure (Nf) data were obtained for the above with simultaneous recording of the load-time and energy-time traces. The extent of impact damage for glass and kevlar composites was interpreted using final delamination area maps (tracings). Results for all the three composites showed that with an increase in drop numbers, the peak load (PL) steadily decreased while the total energy (Et) increased, until failure. Also, as the incident energy (Ein) was varied in arithmetic progression, the number of drops to failure (Nf) varied in harmonic progression. Finally it was concluded that repeated drop tests with final delamination area maps assist in understanding the impact damage tolerance of polymer composites.