ON THE BEARING STRENGTH OF BOLTED GRAPHITE EPOXY LAMINATES

One of the basic failure modes of bolted composite laminates is bearing failure. This mode of failure occurs in the material immediately adjacent to the contact points of bolt and laminate, and is caused primarily by compressive stresses acting on the hole boundary. The results of an experimental program which measured the bearing strengths of two different types of graphite/epoxy specimens are presented. The influence on the bearing strength of several important parameters including lateral constraint and ply orientation are shown. Strains were measured in the vicinity of the loaded hole to quantify the extent of bearing failure. A new approach to predicting bearing failure is outlined. The Delamination Buckling Model (DBM) assumes that ply buckling following delaminations is a major feature of bearing failure. Quantitatively good agreement was found between experiment and model results.