Effect of Washer Type on Bearing Strength of Bolted-Joint Laminated Composites

There are various parameters for bolted joints used in so many industries. The main objective of this work was to investigate the influence of washer type as a bolting parameter on the bearing strength of bolted joints in laminated composites. Therefore, by using three different washer types; flat washer, spring washer and tooth lock washer, an experimental study was performed. Quasi-isotropic glass-fibre reinforced epoxy laminated composites were used in the study. Four different tightening torques ( T = 2, 3, 4, 5 Nm) were chosen for the bolted joints in the experiments, for each washer type. E/W ratio was chosen as 0.25, 0.5, 0.75 and 1 in order to investigate damage modes of composite samples. It was applied tensile test, through a centroidal axis, on each specimen. From these tests, load-displacement curves of the specimens were drawn. The maximum failure loads and bearing strengths of the bolted joints were obtained from the load-displacement curves. From the experimental results, it is noted that bearing strength of the specimens with flat washer is higher than the specimens with tooth lock and spring washer, respectively. Also, it is concluded that higher tightening torque increases the bearing strength, and E/W ratio should be determined as larger than 0.25 for a damage tolerant design in terms of bearing strength.