Effect of back pressure on impact and compression-after-impact characteristics of composites

Low velocity impact and compression-after-impact characteristics of a typical plain weave E-glass/epoxy composite are studied experimentally. Atmospheric pressure was maintained on the top surface and different pressures were applied on the rear side during impact experiments. Pressure on the rear side of the impacted plate is referred to as back pressure in further discussion. Effect of back pressure on the impact behavior is studied. It is observed that the variation in peak contact force and maximum central deflection are governed by two opposing phenomena. The parameters influencing the opposing phenomena are: induced curvature because of back pressure, effective pre-stressing and effective thickness. The incident impact energy was the same in all the experiments. Post-impact compressive strength was also investigated.