Serviceability of Composites Surface Damages

Abstract

Characterization of surface damage of composites is an important step in serviceability and maintenance considerations for many composite structures. Herein we treat the worst configuration of surface damages in the form of a partial through scratch (or crack). A rigorous characterization of a damage of this type requires three-dimensional stress analyses which are necessarily complex in either analytical form or finite-element calculation. As an alternative, we proposed an analytical model wherein the form of the stress distribution is assumed with suitable parameters to be evaluated by force and moment equilibrium. The salient feature of this model is that the complex stress distribution (on the cross-sectional area of interest) is partitioned or zoned by appealing to physical reasoning. The stress components within these zones are represented by power function distributions. The result is an analytical model, sufficiently tractable to be useful for interactive design and sufficiently accurate to correlate experimental observation both quantitatively and qualitatively for several graphite-epoxy laminates and configurations of current interest.