Fiber optic sensors for flow and health monitoring of resin transfer molded composite structures

This paper proposes the use of fiber optic sensors for flow and health monitoring of resin transfer molded (RTM) composite structures. Both fiber Bragg gratings (FBG) and etched fiber sensors have been embedded in composite panels. To this end, a laboratory scale RTM apparatus was designed and implemented with the capability of visually monitoring the resin filling process as well as embedding fiber optic sensors. Tensile test specimens containing embedded FBG sensors with the capability to measure strain have been produced. These sensors have been characterized and evaluated using strain gage and a tensile testing machine. Furthermore, etched fiber sensors that have the capability of detecting the presence of resin have also been fabricated, embedded and tested in conjunction with the FBG sensors. The combined sensor system has proven to be capable of detecting the presence of resin at various locations as it is injected into the mold thus ensuring the quality of the manufactured component and subsequently monitor the health of the component in service.