Strength enhancement of bonded composite laminate joints reinforced by composite pins

Abstract

This paper presents an experimental and numerical investigation in the static strength enhancement of composite laminate Single Lap bonded Joints (SLJ), reinforced by pins made of Uni-Directional (UD) fibre reinforced plastic composite materials. Bonded lap joint specimens were experimentally tested in tension to obtain the failure loads and failure modes. The specimens were subsequently benchmarked against the hybrid version of the joint resulted from the introduction of composite Pins. The Pin reinforcement enhanced the hybrid single lap joint strength by an average of 19.1% increase. Numerical models generated were used for correlation with the experimental results. Numerical and experimental results observation indicated that increased strength of the hybrid bonded/Pinned joint was partly attributed to the load sharing between the adhesive and the Pin past the adhesive failure initiation as well as to the enhanced out-of-plane bending stiffness after the Pin introduction on the lap joint. Numerical investigations were performed as well with hybrid SLJ reinforced by composite pins versus designs employing metallic Pins. The simulations showed that for the investigated lap joint design parameters, the hybrid metallic pin joint failed at a higher failure load. Nevertheless, the hybrid joint utilizing the composite Pin could benefit from the enhanced corrosion resistance properties. In the case of applying a larger composite Pin diameter and/or rearranging the fibre orientation in the Pin, the hybrid SLJs could potentially achieve higher strength characteristics before the adhesive bond ultimate failure in relation to the steel Pin, as well as resulting to additional weight saving up to 46.9%.