NUMERICAL STUDIES ON BOLTED/BONDED LAMINA TED COMPOSITE STRUCTURES

Abstract

The use of advanced FRP composite structural materials is growing worldwide continuously. The behavior of joints in FRP composite structures is quite complex phenomenon due to (a) the orthotropy of material, (b) the use of dissimilar materials in joints, and (c) the presence of various couplings in laminated composites. So there is a need to understand the behaviour of joints in such structures. The quality of the design of joints affects directly the durability and reliability of the structure. If the joints are not properly designed than it can lead to the catastrophic failure of the structure without failing any of its structural components. In composite structures, three types of joints are commonly used, namely, mechanically fastened joints, adhesively bonded joints, and hybrid mechanically fastened/adhesively bonded joints. In this dissertation work, various numerical studies to evaluate the performance of bolted and bonded joints at coupon level as well as system level have been carried out. At coupon level, effect of various parameters on interlaminar normal stress has been studied. The parameters included in this study are laminate stacking sequence, lay-up, loading nature, bolt pretension. Effect of washer size on performance of bolted joint was also considered. Comparison of hybrid (solid as well as shell) model v/s solid model was also included in the coupon level studies. At system level, performance of bolted and bonded hollow box girder subjected to bending and pure torsion was studied. The effect of diaphragms on the performance of hollow boxgirder subjected to pure torsion was also included in the study. It was concluded that the proper selection of the above listed parameters can help to control the interlaminar normal stress, which is one of the common reason behind the failure of composite joints and thus composite structures. The other conclusion was made that the structure with bonded joints performs better than the structure with bolted joints in terms of deflection and stresses.