Predicting failure mechanisms of aerospace‐grade polymer matrix composites in open hole tension: Correlation of experimental, simulation, and analytical methods

Abstract The open‐hole test approach is widely used in the aerospace industry to compute notched design allowable strengths representing the presence of fastener holes or structural flaws on aerostructures. The test determines the force necessitated to permanently deform fiber‐reinforced polymer‐matrix composite materials having a centrally located hole. The hole having an adjustable diameter generates a stress concentration site with a decreased cross‐sectional area compared to the mechanical performance of a complete cross‐sectional area. This study proposes a novel approach to determine the optimum open‐hole diameter of carbon fiber‐reinforced epoxy matrix composite materials with three different stacking sequences. Experimental mechanical tests, per ASTM D5766, yield tensile strengths varying from 352.4 MPa up to 797.9 MPa. The failure mechanism of the anisotropic composite laminae is fiber‐dominated based on the Tsa‐Wu criterion and Scanning Electron Microscope images. Finite element simulation results align with experimental test results to predict the tensile strength with a maximum of 8.8% error margin. The Digital Image Correlation technique, complemented with finite element results, visually illustrates stress‐concentration sites and crack propagation directions for different layup sequences. Last, the presented approach manifests the optimum hole diameter for different stacking orientations as 5.54, 8.44, and 10.44 mm, minimizing stress concentration effects. The technique for the optimum hole diameter shall have further implications with artificial intelligence tools to advance aerostructural efficiency. Highlights This study revises the ASTM D5766 standard for the optimum hole diameter. Anisotropic composite laminae show a fiber‐dominated failure mechanism. ASTM D5766 experiments evaluate the mechanical performance for layups. DIC and FEM strain maps visually highlight the crack propagation directions. The optimum hole diameter is predicted to be around 6 mm for the [45/0/−45/90]_2s.