NUMERICAL AND EXPERIMENTAL FAILURE ANALYSIS OF COMPOSITE LAMINATES WITH BOLTED JOINTS UNDER BENDING LOADS

A three-dimensional contact mechanics analysis has been successfully made on the composite laminates with bolted joints under bending loads. The AS4/3501-6 laminates of [0(8)/90(8)]s and [90(8)/0(8)]s lay-up with two types of countersunk bolted joints, MS-24UNF-3A (psi = 80-degrees) and NAS-24UNJF-3A (psi = 100-degrees), subjected to bending loads are analyzed, respectively. The effects of friction, stacking sequence and countersunk bolt head on the contact tractions around the bolted joint are studied systematically. The progressive failure analysis based on the maximum stress theory, Ye delamination criterion and the complete ply failure approach is performed for predicting the maximum bending load that the laminate can sustain before it catastrophically fails. Toward this end, experimental tests were also conducted to measure the maximum bending load for the laminates with the countersunk bolted joints under bending loads. From the results, it is shown that the joint configuration of [90(8)/O(8)]s laminate and NAS-24UNJF-3A (psi = 100-degrees) countersunk bolt has more higher bending strength while the joint configuration of [0(8)/90(8)]s laminate and NAS-24UNJF-3A (psi = 100-degrees) countersunk bolt has more higher bending stiffness. Good agreement between the computed and experimental results shows the applicability of the technique developed. The present work should be of help for the design of composite laminates with the countersunk bolted joints.