Damage detection of hybrid aramid/metal–PVB composite materials using optical fiber sensors

Embedding optical fiber sensors within laminar thermoplastic composite material results in forming a system known as «smart structure». These sensors present the information about the inner structure health during the material exploitation and especially in the case of exterior impacts when a geometric configuration or the property changes of the material should be expected. This paper evaluates the feasibility of the real-time monitoring of indentation and low energy impact damage in composite laminates from indentation loading and Charpy pendulum impact, using the embedded intensity-based optical fiber sensors. An optical fiber sensing system, which relies solely on monitoring light intensity for providing the indication of the composite structural health, offers simplicity in design and cost-effectiveness. For this, aramid/polyvinylbutyral (PVB) and aramid/metal/PVB laminates with embedded optical fibers were fabricated. Four configurations of woven composites were tested, namely, aramid/PVB, and aramid/metal/PVB in three stacking sequences of aramid and metallic woven layers. The initiation of damage and fracture during testing was detected by observation of the intensity drop of light signal transmitted through an optical fiber