The development and evaluation of an experimental apparatus for the investigation of fastener pull-through failure in graphite-epoxy laminates.

Abstract

This thesis examines the failure at a fastener hole in a composite fuel tank skin due to hydraulic ram; i.e. fluid pressure due to a penetrating projectile. An experimental apparatus was set up to investigate the triaxial loading conditions at the fastener hole so that an M-P-N failure surface could be developed for the graphite-epoxy laminate. An expression was derived to predict the bending moment at the fastener in terms of the pull force on the fastener and the axial force in the plate. Aluminum specimens were tested and the results were compared with the predicted results to validate the experimental procedure. The experimental results were found to not be repeatable, and hence a correlation with the predicted results was not appropriate. The non-repeatability could not be explained. Composite specimens were fabricated and prepared for testing. Experimental values for the ultimate pure pull force, P, ultimate pure bending moment, M, and ultimate pure axial force, N, were obtained.