Stress analysis of finger joints in pultruded GRP materials

Pre-formed composite components have the potential to provide an economical alternative to traditional construction techniques for the manufacture of ship structures. The marine industry at present employs the use of aluminium extrusions in the construction of decks and superstructures that could be replaced with pultruded glass-reinforced plastic (GRP) profiles. The length of the pultruded section is limited and therefore, efficient and economic jointing techniques must be developed that can withstand the loads applied to ship structures. This paper evaluates finger joints in GRP components manufactured from material that models pultruded construction. Various joint geometries are examined, load displacement behaviour is established and thermoelastic stress analysis (TSA) is used to provide the full field stress distribution over the joint. Calibration techniques are described for the TSA. The results of the TSA are compared with the load displacement behaviour. It is shown that by increasing fingertip angle there is a decrease in load carrying capacity, a decrease in shear stress and an increase in stress concentration factor at the finger joint tip. The results from the experimental work were used to validate a numerical model that provides data for initial joint optimisation.