Penetration into Glass/Epoxy Composite Laminates

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Abstract
A new method using laser Doppler anemometry (LDA) was employed to measure the force history of (0°2/90°2). E-glass/epoxy laminates struck by hemispherically tipped projectiles. The striking velocity of the 35.5 g projectiles ranged from 18 m/s to 80 m/s. The ballistic limit for these 2.8 mm thick laminates was at ≈ 60 m/s. It was found that the highest impact force occurred at the ballistic limit, and that the peak impact force in each test was proportional to the initial velocity of the projectile when the specimen was not seriously damaged. Beyond the ballistic limit, the peak impact force was reduced slightly. Further, the magnitudes of the peak force and the absorbed energy of the laminates at the ballistic limit were more than twice those loaded quasi-statically; and the dynamic friction force was also found to be approximately 1.5 times larger. These results indicate a significant rate effect. Surprisingly, the effect of boundary sliding was found to not affect the peak impact force.