FAILURE MODES IN COMPOSITE JOINTS A FINITE ELEMENT STUDY Efstathios E. Theotokoglou Department of Engineering Science, Section of Mechanics The National Technical University of Athens GR-157 73 Athens, Greece SUMMARY: The aim of this paper is to improve the efficiency of T-Joints placed in high speed marine vessels. The behaviour of such joints is very complex since it involves several types of materials such as GRP, foam material as well as glue filler. The material and geometry discontinuities cause stress concentrations in T-joints which can initiate interlaminar or fatigue cracks. A crack propagating between the connected laminate and the attachment lap has been evaluated using the crack flank displacement method in conjunction with the finite element method. Numerical results are presented for the stress intensity factors in the case of T-joints subjected to lateral loads. KEYWORDS: fibre reinforced plastic, T-joints, sandwich material, GRP-laminates, interface crack, finite element analysis, stress intensity factors. INTRODUCTION The Use of FRP (Fibre Reinforced Plastic) sandwich materials for large maritime vessels has in the past years increased enormously, due to the mechanical advantages of the material, especially the high strength/stiffness to weight ratio, high dynamical damping and low thermal conductivity [1]. Apart from the above-mentioned advantages of the FRP sandwich material, one of the major mechanical drawbacks is the difficulty of joining sandwich panels. In maritime vessels such sandwich panel joints occur in very large numbers where the T-joint between hull and bulkhead is the most prelevant connection type. Due to the fact that the FRP face laminates of the sandwich structure are usually thin, the introduction of concentrated point or line loads leads to inexpedient local disturbances [2,3].