The effects of curvature and internal pressure on the compression-after-impact strength of composite laminates

This work presents an experimental characterization of the curvature effects on the compression-after-impact strength of laminated composite shells. Curved panels impacted on the outer (convex) face and with normal pressure on the inner (concave) face with three different curvatures at three different impact energy levels were tested. A compression-after-impact testing setup was designed and implemented to evaluate the impact-induced damage tolerance of the composite shells. An analytical modeling methodology for compression-after-impact strength predictions based on the Mar-Lin and Whitney-Nuismer failure criteria is also proposed. The approach proposed herein consists of replacing the damaged area of the impacted coupon by an equivalent hole. The analytical compression-after-impact predictions obtained using the Mar-Lin and Whitney-Nuismer failure criteria were compared with experimental results. A good agreement between analytical predictions and experimental results was found. The experimental results also indicate that the compressive residual strength of the composite shells is significantly affected by the shell curvature and internal pressure effects.