QUASI-STATIC AND BALLISTIC PERFORATION OF CARBON-FIBER LAMINATES

The partial and complete perforation of woven carbon fiber/epoxy laminates with thicknesses ranging from 1.3 to 6.6 mm by 60-degrees cylindro-conical hard steel strikers at normal incidence has been examined under both quasi-static and dynamic conditions. Quasi-static experiments were conducted in a standard testing machine at rates ranging from 0.012 to 6.5 s-1, where the load-deflection was obtained. Ballistic tests employed a 12.7 mm diameter projectile with an aspect ratio of three fired from either a compressed gas or a powder gun at speeds varying from 30 to 310 m/s, with the initial and final velocity (when present) of the striker always measured, in addition to selected high-speed photographic recording. The damaged samples were carefully examined with respect to failure modes. Major mechanisms of the deformation and damage processes were modelled on the basis of energy absorption, including global plate deflection, fiber breakage, delamination, formation and bending of petals, hole enlargement and friction between strker and sample. For the dynamic case, the predictions were 70-96% of the observed expenditure level. This is considered to be due to the absence in the analysis of factors such as inertia, strain-rate and wave propagation effects, matrix shearing and fragmentation, as well as obliquity and rotation motion of the striker. The correspondence in the case of static loading was considerably poorer, indicating substantial and nonmeasurable energy absorption by the test apparatus, including substantial frictional dissipation in the specimen holder and between sample and penetrator.