Ballistic impact response of 3-D four-step braided glass/epoxy composites

The ballistic impact response of three-dimensional four-step braided textile composites struck by a 36.1 g hemispherical tip-ended rigid cylindrical projectile is studied in the present research. A series of quasi-static punch tests using a hemispherical indentor with the same diameter as that used in dynamic impact tests have been conducted to investigate the progressive damage modes of the glass/epoxy composite target and to obtain the punch load-displacement relationship. A pneumatic launcher is used to perform, dynamic impact tests and the projectile is fired with an incident velocity ranging from 60 upto 180 m/s. The experimental ballistic limit of the target is determined to be near 69 m/s. Commercially available finite element analysis code MARC is incorporated with the constitutive relationship for three-dimensional four-step braided composites and the proposed quasistatic penetration model to simulate the dynamic impact response, An energy consideration is adopted for predicting the projectile's residual (or terminal) velocity. The numerical simulation based on the quasi-static elastic properties of the target slightly overestimates the projectile terminal velocity. When the target's elastic moduli used for numerical simulation are increased by 1.2 times the quasi-static values, very good agreement is found between the simulated terminal velocities and test results. In addition, the predicted ballistic limit is very close to that determined from the impact tests.