Energy harvesting for damage assessment: A novel approach for detecting and evaluating structural defects in composite laminates

The presence of cutouts within mechanical equipment and systems can give rise to catastrophic stress concentrations and local buckling, leading to the initiation and propagation of damage. In addressing this issue, we leverage the concept of energy harvesting as a diagnostic approach. Beyond conventional fault diagnosis methods that rely solely on measuring changes in displacement amplitude, we propose an innovative method that harnesses the generated voltage. This novel approach investigates the impact of cutouts (holes) with varying diameters, which represent critical defects, on energy harvesting and displacement amplitude within 8-layer E-glass/epoxy composite specimens. Piezoelectric transducers are employed to execute energy harvesting, complemented by a laser displacement sensor for capturing sample displacement amplitudes. A bespoke measuring circuit is developed to quantify the stored voltage in a capacitor. Analysis of the findings reveals that the presence of damage, its severity, and its spatial distribution induce alterations akin to changes observed in displacement amplitudes. The study demonstrated that after applying the first cutout, a 75% and 65% reduction in harvested energy and a 60% and 46% decrease in displacement amplitude occurred for 14 and 10 mm cutouts respectively. By increasing the number of cutouts, these parameters depicted decreasing trends with a lower intensity. This alternative method offers an efficient, effective, and low-cost strategy for detecting and assessing damage and its severity in composite laminates. By demonstrating the correlation between damage-induced variations in harvested energy and conventional displacement measurements, our study contributes to advancing non-destructive evaluation techniques for composite structures. The effectiveness, cheapness, and convenience in implementation and detecting defects in composite laminates, are the practical implications and potential applications of the current work.