Static and Low-Velocity Impact Response Characteristics of Pultruded Hybrid Glass-Graphite/Epoxy Composite Beams

Abstract

The influence of hybridization on the crashworthiness and energy-absorption characteristics of pultruded glass-graphite/epoxy composite beams was investigated. Lowvelocity drop weight instrumented impact tests were conducted on these hybrid composites to determine the load-deformation behavior for evaluating the impact performance in terms of the ductility index, damage initiation, propagation, and total absorbed energies. Three-point static flexural tests were also conducted to compare the static load-deformation characteristics with those of the dynamic low-velocity impact tests. The behavior under both static and dynamic loading conditions was simulated using finite element modeling procedures to identify the failure mechanisms for optimizing the performance of pultruded hybrid composites. Experimental results show that the load and strain to failure of all-graphite/epoxy, all-glass/epoxy and other hybrid composites obtained from impact tests are significantly higher as compared to the static test data. The load-bearing capability of composites after damage initiation (which is dictated by the ductility and failure index) has shown marked improvement for the graphite-outside hybrids when compared with the all-graphite, all-glass, and glass-outside hybrids. The high strain to failure glass fibers absorb considerably higher energy before ultimate failure compared to the brittle graphite fibers; as a result, the fiber content and geometric placement of each type of fiber significantly influenced the energy-absorption characteristics of hybrids. Results indicate that the energy-absorption behavior of pultruded hybrids predicted using finite element modeling is in close agreement with the behavior characterized from experimental impact tests. The effectiveness ofhybridization to improve the impact performance of composites was demonstrated.