An FE analysis of the stresses in pultruded GRP single-bolt tension joints and their implications for joint design

FE (Finite Element) analysis is used to determine stresses on critical planes and around the hole edge in a two-dimensional model of a single-bolt tension joint in pultruded GRP (Glass Reinforced Plastic) plate material. The analysis takes account of bolt–hole clearance and friction at the contact surfaces between the bolt shank and the hole. It is shown that even when the hole clearance is nominally zero (∼0.2 mm) critical stress distributions, normalized with respect to the far field stress, are not invariant but change as the tension increases. Friction between the bolt shank and the hole and the small hole clearance (∼0.2 mm) are the principal factors which cause the zone of contact (defined by the angle it subtends at the centre of the bolt) to increase with increasing tension, and produce significant changes in the stress distributions at critical locations. These observations cast doubt on the validity of the simplified method for joint design given in the EUROCOMP code [In: Clarke JL, editor. Structural design of polymer composites – EUROCOMP design code and handbook. London: E.&F.N. Spon; 1996], because the method relies on normalized critical stress distributions remaining unchanged as the tension applied to the joint increases.