Mechanical property of single-bolted composite laminates

In order to investigate the effects of different geometrical parameters and pretightening loads on failure mode and bearing strength, a large number of single-bolted T300/QY8911 composite laminates were tested under static tension load. Box-plot was used to extract the singular testing values of bearing strength and effective statistical values were obtained. T-test method of independent samples was used to study how much pretightening loads influence bearing strength. The results show that the geometrical parameters, such as ratios of width to hole diameter (w/d) and edge distance to hole diameter (e/d), remarkably influence failure mode and bearing strength. Net-section failure will occur when w/d is smaller than 4, and shear-out failure will occur when e/d is smaller than 2. Bearing failure or bearing and shear-out combined failure will occur when w/d is greater than 4 and e/d is greater than 2. There is an optimal combination of geometrical parameters to achieve the highest bearing strength. For most of specimens, pretightening loads do not explicitly influence bearing strength.