Effect of Pin Insertion Angle on Mechanical Performance of Hybrid Scarf Joint in FRP Laminates

Abstract

In the aviation industry, structural sub-components like wing spars, landing gear struts, and fuselage frames are often assembled using a scarf joint. The bond strength in the scarf joint is a governing mechanical property in the composite structure. The addition of fasteners to produce a hybrid fail-safe joint can mitigate the substantial requirement of bond strength in scarf joints. However, material discontinuity at such joints may cause abrupt stress concentration leading to catastrophic failure. The current study presents a numerical investigation into the effect of the insertion angle of pinning reinforcement on the mechanical property of a hybrid scarf joint using unidirectional carbon fiber reinforced polymer (CFRP) as adherends and epoxy as adhesive material. An 8- noded reduced integrated solid element (C3D8R) incorporating continuum damage mechanics is used to model the adherends and fasteners in the joint. Similarly, the adhesive is modelled using the COH3D8 element. 3D Hashin criteria are included in the ABAQUS-UMAT subroutine to simulate localized mode of failure and stress concentration in anisotropic laminates. The cohesive zone modelling is used to predict the strength of the adhesive bond. The numerically obtained peel stress and shear stresses for varying pin insertion angles are analyzed along with different failure modes in the laminate under the quasistatic longitudinal tensile test. The knowledge from the study will be helpful for the structural analysis of scarf joints with the pin inserted in the adhesive region.