Optical fibers in composite materials: The effects on mechanical properties under flexural and tensile loading and acoustic emission monitoring

As the demands of materials in practical applications become more sophisticated, multiple technology streams have moved towards a smarter future, incorporating monitoring techniques to validate safety and performance. Optical fiber sensors offer a route to embedded sensing technology within new composite materials, but an understanding of resulting modifications to structural performance following inclusion requires assessment. This work studies three optical fibers (125 μm and 89 μm diameter with dual-layer acrylate coating and 80 μm diameter with polyimide coating) embedded in the composite material. Optical fiber placement and the effects of sensor orientation relative to fiber reinforcement plies, weave configurations, and stacking order considerations under varied load applications are considered and discussed. Empirical results on the effects of fiber coating composition and thickness on composite material samples were collected under flexural and tensile loading. With the aid of non-contact acoustic emissions monitoring, the effects of interfacial interaction between embedded sensors and surrounding composite materials have been assessed compared to elastic wave responses. This considered physical phenomena to map and assess the effects of introducing this structural discontinuity on these materials’ mechanical testing and capability. In doing so, this study adds to a gap in the existing literature by investigating the effects of the multiple variables for fiber sensor embedment in practical applications to move towards smarter material solutions.