Out of plane deformation measurements of axially loaded composite materials using electronic speckle pattern interferometry
Abstract
The use of composite materials is fairly new and becoming increasingly pervasive. Composite materials are found in applications ranging from aircraft structures, automobile parts, to both heavy and light ballistic armor. The use of composite materials is recent, therefore existing theory and data on material performance is an opportunity area for development.
Strategies for theory improvement include development of computational methods to predict the energy required to create a fracture and the energy levels required to sustain a rate of crack propagation. It is necessary to generate data on these energy levels to test the validity of the computational predictions.
Previous methods to determine these energy levels were to measure the length of the crack over a given number of loading cycles. These techniques adequately address energy expended in the in-plane direction, but ignore energy expended in deforming the material in the out-of-plane direction. The focus of this study is to use Electronic Speckle Pattern Interferometry (ESPI) to measure the out-of-plane deformation of graphite/epoxy samples under quasi-static cyclical uni-axial loading.