Triple-exposure shearography for the measurement of surface slopes

Abstract

Investigations comprising of experimental observations and analytical study have been systematically executed to evaluate the compressive response of a particular composite system which has potential for structural armor applications. The material being a multi-layered thick laminate is a random mode stacking of bi-axial, plain weave S2-Glass/S2-Glass fiber yarns with polyester resin (Cycom 4102) as binder material, thirty two percent by weight. Attention is focused to understand the three dimensional macroscopic behavior of the material subjected to unidirectional quasi-static and dynamic compressive loading conditions using state of the art procedures. Quasi-static (low to medium strain rates) experimental investigations were carried out on an MTS test system while the dynamic response was observed using the split Hopkinson pressure bar test equipment and on a modified Hopkinson pressure bar termed direct disk impact. A comparison of the results of the two setup is presented. The uniformity of the material's response is verified for different sized and shaped specimens. The material's elastic constants, strength and strain rate effects in the region of 10-5 - 103 sec-1 are reported in this paper. The directional failure modes under compressive loading are discussed with the aid of scanning electron micrographs. Based upon the physical construction of the composite, a unit cell representation is presented for analytical modeling. The numerical results of this model are compared to that of the experiment results obtained.