PSI - Issue 71

M Mohan Kumar et al. / Procedia Structural Integrity 71 (2025) 372–379

373

laminate. This study aims to evaluate the tensile strength of laminated composite panels in three configurations: undamaged, damaged (50mm cut-out), and scarf repaired. Using Carbon/Epoxy prepreg, sixteen-ply [+45/- 45/0/0/90/45/0/0]s quasi-isotropic laminates (1000 x 300 x 3.3 mm) are analyzed. The strength of each configuration is assessed to determine the impact of damage on strength reduction and the effectiveness of repairs in restoring original strength. 3D analysis is performed using commercial software, numerical predictions based on the Tsai-Wu failure criterion, while experimental tests are conducted using a Servo-hydraulic Universal Testing Machine. Results from both methods are compared for validation.

Fig. 1. Schematic representation of scarf repair technique. In general, FRPs typically integrate structural fibers like carbon, glass, or aramid with a plastic matrix such as epoxy or polyester, providing enhanced strength and stiffness. Composites offer advantages like improved strength-to-weight ratio, stiffness, fatigue resistance, and corrosion resistance, making them superior to conventional materials. Scarf repair is a common method for restoring damaged composite structures. It involves tapering the damaged area at a shallow angle to create a smooth transition between the parent material and the repair patch. Composite layers, matching the original laminate, are then bonded using a high-performance adhesive like Redux 319A. This technique increases bonding surface area, reduces stress concentrations, and restores the structural integrity of the composite part. Nomenclature FI Failure Indices FE Finite Element FEA Finite Element Analysis 3D Three Dimensional CFRP Carbon Fiber Reinforced Polymers σ Stress N/mm 2 2. Problem Definition The objective of the present study is to evaluate the tensile strength of repaired laminated composite panels and to investigate the performance of three distinct configurations: the undamaged panel, the panel with a centered hole, and the repaired panel under tensile loading conditions.

Fig. 2. Geometrical details of the undamaged, damaged and a scarf repaired CFRP panels. For this investigation, Carbon/Epoxy prepreg material will be employed to construct sixteen-ply (1000 x 300mm x 3.3mm) quasi-isotropic laminates with the stacking sequence [+45/-45/0/0/90/45/0/0] S. Laminate Properties: The laminate utilized in this study is composed of 16 layers of CFRP AS4/914 with a lamina thickness of 0.20625 mm, the geometrical specifications are illustrated in Fig. 2, with all dimensions provided in millimeters. The stacking sequence