Application of Mechano-Luminescence-Optoelectronic Composites for Delamination Detection in Fiber Reinforced Polymer Composites¹

Fiber-reinforced polymer (FRP) composites have attracted significant attention from the aerospace industry in recent years. FRP composites have the advantage of being light weight, high strength, and resistant to corrosion making them an attractive option for various applications in the aerospace industry. However, FRP composites are prone to delamination which can eventually compromise structural integrity leading to sudden failure. An effective damage detection methodology is therefore necessary to monitor delamination in structures. In this study, mechano-luminescence-optoelectronic (MLO) composites were integrated with FRP composites to create MLO-FRP test coupons for delamination detection. The MLO composites were prepared by coupling a poly(3-hexylthiophene) (P3HT)-based sensor with a copper dopped zinc sulfide (ZnS:Cu) composite. MLO composites were attached to the surface of FRP composites to create MLO-FRP test coupons. The MLO-FRP test coupon was mounted on a 3-point bending load frame and subjected to cyclic loading and unloadings at various displacements with the first displacement starting from zero to 5 mm, the second displacement starting from zero to 6 mm, and so on. A direct current (DC) voltage was recorded from the MLO composites at a constant loading rate to validate its DC-based strain sensing capability. Other parameters such as applied load, strain energy release rate, and strain were also obtained with the aim of tracking delamination propagation in FRP composites. Results showed that MLO composites were sensitive to delamination propagation highlighting their potential to be used in structures for health monitoring.