Numerical analysis on bonding stress of carbon fibre reinforced epoxy

Abstract

The application of fibre reinforced polymer (FRP) composites in pipelines repairing and rehabilitation process revolutionizes the whole oil and gas industry especially in a condition which repair technique is hard to be implemented. The bond strength between FRP and the pipeline metal is the major element in determining the system strength. Numerous researchers studied the adhesion failure between FRP and metal using both experimental work and finite element (FE) simulation. However, the evaluation of bond strength has been specifically constraint within the bonding system and materials used only. This study aimed to simulate the pipeline repair system and investigate the adhesion shear stress acting at the joint using FE analysis. Double strap joint (DSJ) samples consisted of carbon fibre reinforced epoxy (CFRE) and ASTM A36 steel as the adherend were prepared to model the repairing system using SIKADUR 330 epoxy as the adhesive. A number of parametric tests was performed to obtain material data input for FE simulation. FE model of the DSJ samples was developed using ABAQUS software and a linear cohesive zone model was applied to model the behaviour of the cohesive layer. Laboratory tensile test was also conducted to validate the FE simulation results. The maximum load value in simulation result showed 9.8% higher than the result from experimental work while deeper analysis in stress distribution data provided an estimation of 69.1% effective length of the bonded area. A parametric study was conducted to evaluate the effect on the bond strength by varying adherend’s thickness and elastic modulus. For CFRE cases, the maximum applied load increased non-linearly with average increments of 2.08% and 1.25 % respectively, while adhesive horizontal displacement non-linearly decreased with average decrements of 6.16% and 5.62%, respectively as its thickness and modulus increased. Meanwhile, for ASTM A36 steel cases, a slight decrement was observed for maximum applied load with average decrements of 0.33% and 0.16%, while adhesive horizontal displacement non-linearly decreased with average decrements of 2.21% and 2.37 % respectively as its thickness and modulus increased. In conclusion, the stiffness of the bonded structure was influenced by both parameters, which beneficial in structural design.