Reply by Authors to R. Prabhakaran

Abstract

E comment by Professor Prabhakaran will be addressed in the order presented. 1) We acknowledge that interlaminar stresses are an important three-dimensional localized effect at the hole boundary. However, solutions require addressing the complete three-dimensional elasticity boundary value problem. No analytic solution to this extremely complex problem currently exists for general loadings surrounding an open hole in an arbitrary orthotropic laminate. Tang explains the complexity of this problem relative to open holes, and also provides an extensive reference list. The authors recognized that modeling all observed phenomenon would have required a three-dimensional, nonlinear, inelastic stress analysis. We chose a phenomenological approach to permit use of available and general two-dimensional, linear-elastic, closedform analysis in conjunction with known material failure criteria. The wisdom of our analytic approach and associated approximations was evaluated by correlating predictions with test data which we reported in our paper. l 2) Our paper demonstrates that the analytic procedure used, within acceptable engineering accuracy, predicts the effect of hole size on laminate tensile strength. Specimen width to diameter ratios were maintained constant. We question the general validity of Prabhakaran's comment concerning inherent size effect . . . of unnotched tensile strength with width. Prabhakaran arrives at this conclusion based on data obtained from specimens fabricated from E-glass fabric/epoxy. Nonlinear and inelastic mechanical behavior are oresent in glass-epoxy and initiate at low strains (.004 mm/mm) relative to final failure (.029 mm/mm). Glassepoxy mechanical behavior is not similar to graphite-epoxy behavior which exhibits relatively linear-elastic behavior to tensile failure. All laminate strength data were obtained from specimens loaded to failure in tension, lamina unnotched strength data were obtained from sandwich beam and rail-shear specimens. 3) The important differences between our analytic procedure and the two-parameter models are not those which Prabhakaran discusses. Our objective was to predict