Experimental and numerical analysis of damage progression in composite cylinders with cutouts under combined loading using structural health monitoring techniques

The study investigates the damage progression within a long and hollow axisymmetric composite cylinder with central cutouts, employing both experimental and numerical approaches. The composite cylinder, with a radiusto-thickness ratio of 10 and a length-to-diameter ratio of 10.5 tested under combine loading condition (torsion and compression). Damage accumulation is investigated using acoustic emission, infrared thermography, digital image correlation, and strain gauges. Unsupervised machine learning techniques are utilized to analyze acoustic emission data, facilitating the clustering of damages, with matrix cracking identified as the predominant failure mode resulting from shear stresses. The distribution of failure types varies across the cylinder, culminating in catastrophic failures resulting from the concurrent appearance of these events. A thermal camera captures temperature changes during failure, offering insights into damage initiation and post-global failure. The utilization of the digital image correlation technique enables the acquisition of full-field surface displacement measurements within the specimen including an open hole, thereby revealing the consequential effects of these displacements on the mechanism of failure. Linear static analysis and stiffness reduction-based progressive damage analysis are performed in the Ansys, which underscores study reliability demonstrated through comparisons of load-displacement, torque-rotation curves, and full-field displacement maps between experimental and numerical analyses.