Failure Analyses of Polymer Matrix Composite (PMC) Honeycomb Sandwich Joint Panels

Abstract

The objective of this paper is to investigate the structural behavior and material failure characteristics of polymer-matrix composite (PMC) honeycomb sandwich joint panels under several transverse loads which resulted in web bending as typically experienced by aircraft wing skin. Several PMC honeycomb sandwich joint panels were fabricated as part of the demonstration test elements to provide structural concepts for the High-Speed Civil Transport (HSCT) wing. Test elements were preliminarily designed and sized under design-integration trade studies (DITS) task. Test elements selected for this study included two PMC honeycomb sandwich joint panels; one panel consisted of a honeycomb sandwich wing skin bolted joint by two fiber-reinforced composite spar caps to a honeycomb sandwich spar web; the other panel had the same structural concept except that the composite spar caps were replaced with the titanium ones. Essential components in the sandwich construction were composite face sheets, honeycomb cores, and core-to-facing bonding material. By statically loaded test elements to failure in room temperature, the test was designed to simulate flight load condition of 15 psi fuel over pressurization against the wing spar during supersonic maneuver. Geometric linear and nonlinear finite element models were constructed to simulate the structural behaviors of these test panels. Failure theories such as the Yeh-Stratton, Tsai-Wu, Tsai-Hill, and Maximum Stress and Strain criteria were utilized to predict the first ply failure and the results were compared with experimental data.