High-resolution optical study of the impact of carbon-fibre reinforced polymers with different lay-ups

The impact deformation of carbon-fibre reinforced polymer samples with different lay-ups was studied using high-speed optical techniques. The in-plane deformation of the sample was measured using time-resolved fine-grid analysis. The residual velocities of the projectiles were determined using streak photography and hence the energy dissipated during the penetration was obtained. Both microscopic damage and macroscopic damage to the plates were studied. The deformation, energy dissipation and damage all had a strong dependence on the composite lay-up. Unidirectional composites exhibited anisotropic behaviour and were significantly weaker than the other lay-ups. Though this is intuitively reasonable, this paper gives quantitative measures of this effect. Composite samples examined using the fine-grid technique exhibited cracking in the rear ply suprisingly early in the impact with wide-reaching delamination of this ply. Comparative measurements are presented for polymethylmethacrylate which deformed more isotropically until fragmentation.