Fastener pull-through failure simulation in a laminated composite joint

With the increasing use of bolted joints in composite structures, it becomes crucial to predict the failure load of these joints under out-of-plane loads. The present study explores the pull-through failure mode of bolted joints in composite structures through both numerical and experimental methods. The sandwich specimens were tested using the ASTM D7332. In the numerical study, a user-defined subroutine was developed to investigate the failure modes and mechanisms, as well as damage propagation in sandwich structures and laminated composites progressively. To reduce the dependence of the standard test outputs on geometrical variables, a novel parameter called nominal pull-through strength (SPT) has been defined for laminated composites. This parameter allows the results of structural tests on specimens with standard dimensions to be applied to joints of various sizes in practical applications. Additionally, a simplified procedure for designing composite bolted joints in the pull through mode has been proposed using the SPT parameter. SPT results have been evaluated statistically to find the probability distribution function and determine the strength corresponding to each confidence level.