High-speed 3D digital image correlation of low-velocity impacts on composite plates

Composites are beginning to be used in a variety of different applications throughout industry. However, certification and damage tolerance is a growing concern in many aerospace and marine applications. Transverse impact of composites results in damage in the form of transverse matrix crack, delamination, fiber breakage and permanent deformation. Low-velocity impact experiments were conducted on 3.2 mm thick IM7/977-3 composites with 10 J of energy (1.888 m/s). High-speed digital photography was used to capture impact phenomenon of a composite's back surface. The specimens were speckled to perform 3D digital image correlation to analyze the displacements and strains that occurred on the back surface. The results from this study provide basic knowledge of the impact event such as deformation, strains, residual strains, damage threshold load, transverse matrix crack initiation and propagation.