Failure analysis of composite joints under preload moment and moisture.

In this study, a failure analysis was performed under various conditions numerically and experimentally to investigate the behavior of laminated composite plates which have pin-loaded holes. The main aim of the study is searching the effects of preload moment, moisture and interference-fit on bearing strength, failure load and failure mode in pin-jointed and bolted carbon-epoxy composite plates which were subjected to a traction force. Some of the specimens were kept in the seawater for sixty days before the experimental tests to observe the effect of moisture.Each laminated plates consisted of four laminas and had same stacking sequences. Two different geometrical parameters, end distance to pin diameter ratio and width to pin diameter ratio were considered. End distance to pin diameter ratio and width to pin diameter ratios were determined ranging from one to four and from two to four, respectively. The pre-load moments were applied to the specimens as three and six newton-meter for observing the failures under preload moment. Also, for investigating effect of interference-fit, a pin was produced which has a bigger diameter than hole diameter.The experiments were performed in tension mode on the Instron-1114 Tensile Machine of a crosshead speed of 1mm per minute. Then the average bearing strength values were found. The load versus pin displacement curves were plotted in the experiments. For the numerical study, three-dimensional non-linear contact analyses were conducted using commercial program ANSYS v10.