Preloaded composite panels under high velocity impact

Abstract

Composite structures due to their low strain to failure are regarded as a brittle material and are susceptible to possible impact damage during manufacture, maintenance and in use. This paper describes the influence of tension, compression and hybrid preload on E-glass/polyester composite plates under high velocity impact loading in a velocity range of 185 to 235 m/s. Six layered, E-glass plain weave woven roving [0/90]6 composite panels were made by hand layup method. An innovative preloading apparatus, which is patented with number IRI-83450 was developed to apply the preloading in uniaxial and biaxial directions. This device was used simultaneously with a gas gun to conduct high velocity impact tests. A spherical hard body projectile was used in the impact tests. Uniaxial tension, uniaxial compression and biaxial tension and compression preload were applied to each specimen. To assess the strain rate sensitivity of the material concern under different preloading, three different impact velocities were used. Result showed, the ballistic resistance of the samples with the different preloading condition decreased compared to no preload case. Less variation was observed in exit velocities in the upper impact velocity range test (235 m/s) conducted for all boundary conditions used. A significant increase in the rate of change of residual velocity was observed for the impact velocity of 185.3 m/s compared with that of higher impact velocities tested. Delamination and fiber fracture constituted the major fracture modes followed by matrix fracture.