The response of a glass fibers reinforced epoxy composite to an impact loading

Abstract

The dynamic response of a woven glass fibers reinforced epoxy composite to a planar impact loading is investigated. The composite samples were struck perpendicular to the fibers plane by aluminum 6061-T6 impactors at velocities ranging from 60 to 280 m/s. The free surface velocity of the samples was monitored by VISAR. To highlight the contribution of the resin’s properties versus the role of the composite’s microstructure analogous measurements were carried out on free-of-fibers homogeneous epoxy resin samples. Low-velocity impacts were performed to examine the response of undamaged specimens. Damage processes during the tensile and the compressive stages were activated by application of intermediate and high-velocity impacts. At low-impact velocities the behavior of the composite is primarily dictated by the viscous behavior of the epoxy resin. The role of the microstructure becomes more noticeable at higher impact velocities. Oscillations of the free surface velocity profiles, originating from the reflection and refraction of the waves at the interior interfaces of the composite are observed. Owing to the composite’s microstructure the acceleration duration of the free surface was notably longer than the corresponding duration measured for the homogeneous epoxy samples. It was further found that the compression wave speed increases with the pressure. In contrast with the epoxy samples, in undamaged composite samples the speeds of the compression and release waves are almost identical. Reduction in the release wave speed takes place only after some compression related damage accumulates in the composite. The spall strength of the composite is lower than the one measured for the epoxy but the post spall damage mechanism is somewhat slower.