An Overview of Composite Materials with Emphasis on FRP Systems

This study presents a three-dimensional finite element analysis of adhesively bonded inner-tapered double-lap joints in laminated fibre-reinforced polymer (FRP) composites subjected to longitudinal and transverse loading. The joint configuration incorporates T300/934 graphite/epoxy adherends and an epoxy adhesive, with adhesive taper angles varied from 35° to 45° and composite fibre orientations varied from 0°–90° in steps of 15°. A detailed 3-D finite element model using SOLID185 elements is developed to evaluate stress components (σxx, σyy, σzz, τxy, τyz, τxz) and corresponding displacements within both the adherends and adhesive layer. Results indicate significant sensitivity of normal and shear stresses to fibre orientation and adhesive thickness, with maximum stresses generally occurring at intermediate fibre angles (45°–60°). Adhesive thickness 0.15 mm exhibited the lowest stress concentrations. Under both loading conditions, joints displayed pronounced anisotropic behaviour, and stress transfer efficiency improved with optimized fibre and adhesive angles. The study contributes validated numerical insights for the design of efficient FRP bonded joints and provides guidelines to minimize stress concentrations in high-performance composite structures.