Pin and bolt bearing strength of fibreglass/aluminium laminates

An experimental investigation was carried out on a fibreglass/aluminium (FGA) laminate in order to characterise its behaviour under pinand bolt-bearing conditions. In pin bearing, the limit width-to-diameter and edge distance-to-diameter ratios necessary to avoid unsafe failure modes were lower than those usually quoted for classical laminates. A simple model to design safe pin-bearing joints, previously proposed for fibre-reinforced plastics, was effective also for the FGA. The study of the failure modes suggested that the aluminium layers play a major role in determining failure. The latter was due to the shear buckling of the individual laminae, which were decoupled from each other by extensive delamination/debonding phenomena. Under bolt-bearing conditions, the features of the load–displacement curve allowed for the individuation of two bearing strengths, labelled as ‘damage-bearing strength’ and ‘failure-bearing strength’, respectively. The damage-bearing strength was substantially unaffected by the bolt torque, and was up to 20% higher than the pin-bearing strength. The failure-bearing strength slightly increased with increasing the clamping pressure, achieving values up to 85% larger than the pin-bearing strength. From the microscopic failure modes observed, a possible explanation for the two bolt-bearing strengths recorded was given.