A microstructural study of Gr/Ep composite material subjected to impact

Fracture morphology and texture were observed on the impact generated graphite/epoxy composite fragments. The work identifies and explains changes in the surface texture of the fragments generated at different impact velocities (122 to 610 m/s, 400 to 2000 ft/s) and over a wide range of specimen temperatures (−54 to 24°C, −64 to 75°F). The composite panels were impacted by spherical steel projectiles, and the entire spall was carefully collected after the impact. The spall was differentiated according to different sizes and shapes. A few fragments representing each shape and size were selected to analyze the surface morphology using scanning electron microscopy (SEM). Change in the surface texture was observed according to the different sizes and shapes, and the change in size and shape of the fragments was credited to the change in impact force. The results following from the close and intense observation of several SEM fractographs revealed that the surface texture of the fragments is strongly dependent on the type of forces acting at the point of impact resulting in four different modes of failure: delamination, transverse matrix cracking, fiber fracture and fiber-matrix interface debonding.