Authors: Prabhakar R. Mantena
Abstract: In this paper, investigations on the dynamic response and energy absorption characteristics of different hybrid combinations of glass and graphite fibers in an epoxy matrix are reported. Two types of unidirectional pultruded specimen configurations have been evaluated at an average strain rate of 700-800/s using a modified Split Hopkinson Pressure Bar (SHPB) apparatus. High strain-rate longitudinal compression experiments were performed on cylindrical specimens, with rectangular cross-section specimens subjected to transverse compression loading. A high-speed video camera was used for monitoring crack initiation and propagation, and effects of hybridization on the dynamic response of pultruded hybrid composites evaluated. For a given fiber volume fraction, the placement of glass fibers in inner core results in higher ultimate compressive strength, specific energy absorption and better dynamic performance in general, along with lower density. Under transverse compression loading, however, the location of glass or graphite fibers had no significant effect on the ultimate compressive strength, with the energy absorption of all hybrid combinations almost identical. All-graphite/epoxy composite showed higher specific energy absorption (due to lower density) with all-glass/epoxy composite exhibiting the lowest specific energy absorption.
Keywords: Pultruded composites; hybrids; high strain-rate; compression loading; SHPB; dynamic energy absorption