Local fatigue behaviour of CFRP bolted joints

Before fatigue behaviour of composite bolted joints can be understood a good comprehension of the local behaviour of the fasteners and surrounding composite is needed. Measurements of the local strain between two bolts were made by using strain gauges on composite joints with different configurations. Bolt movement was measured on bolts during cyclic loading. It was found that the presence of the bolt affects the strain development between the bolts. The measured bolt movement and strain loops show the influence of friction forces, bolt pre-stress, and fatigue damage in the joint system on the fatigue behaviour of bolted laminates. Fractographic observation showed that bolted joints tested at high loads sustained severe damage around the bolt holes. The fatigue behaviour of the particular fastener influenced the amount of fatigue damage observed at different bolt holes.