Open hole strength and damage behavior of GFRP and CFRP composites

Fiber-Reinforced Polymer (FRP) composites are increasingly attractive for advanced engineering applications. Notches in structural components are unavoidable in practical applications. Open circular holes, such as bolted connections, are an essential design feature. However, stress concentrations arise, the magnitude of which depends on the material anisotropy and the defect size in the plate. Precise evaluation tools are crucial for designing optimum, safe, lightweight structures. This study investigates the mechanical performance of open-hole Glass/Epoxy Composite (GFRP) and carbon/epoxy composite (CFRP) laminates experimentally and numerically. The effect of varying hole diameters, hole number, and fiber direction on mechanical properties and damage mechanism was investigated with tensile tests and finite element analyses. Higher strength values were obtained in the 0 degrees fiber direction compared to 90 degrees and 45 degrees. The effect of the hole diameter on the tensile strength was enormous, and the strength values decreased as the hole diameter increased. It was observed that the number of holes in the fiber direction had much less effect on the stress-strain curves than the number of holes perpendicular to the fiber direction. The results showed that GFRP has lower notch sensitivity than CFRP because the strength reduction rate with hole size was lower. Open holes ' Stress Concentration Factors (SCF) were determined with finite element analyses. Finite element analyses provided information about the initiation of damage. The normalized strength change curves according to the fiber direction, hole diameter, and hole number were obtained, and equations with a correlation coefficient of at least 90 % were developed according to these curves. Since notch sensitivity is higher in CFRP, the normalized strength is higher in GFRP than in CFRP. Failure analysis was performed for the GFRP composite with 6 mm holes. Tsai-Wu failure theory is utilized in the analysis to predict the damage evolution of open-hole composite laminates subjected to tension loads.