Mechanical/bonded joints for advanced composite structures

The strengths of mechanical-connected and adhesive-bonded joining systems are combined to develop an improved connection system for advanced composite materials. The principle of resistance enhancement is based on the insertion of small diameter pins through an adhesive joint. The pins act as local reinforcement in the most highly stressed regions of the joint, enabling an adhesive joint to carry an increased load prior to failure. In a series of single-lap shear experiments using glass fibre reinforced polymer samples, adhesive-only and pinned-only specimens failed in the joint region. In contrast, many of the pinned/bonded specimens failed away from the joint at a significantly higher load. Insight was gained regarding the influence of the pin material, diameter, number and configuration on the resulting performance. The results demonstrated the potential of pinned/bonded systems as a new method for connecting composite materials. However, further work is necessary to confirm the sensitivity of the results to changes in parameters such as the fibre architecture, adherend geometry, adhesive interface and joint configuration.