Wet deck slamming experiments with a FRP sandwich panel using a network of 16 fibre optic Bragg grating strain sensors

Abstract

Drop test experiments have been performed with a FRP sandwich panel instrumented with a network of 16 fibre optic (FO) Bragg strain sensors, together with conventional electrical strain gauges for control and verification. The drop tests simulate slamming loads on the wet deck of a surface effect ship (SES). The objectives were to show the possibility of using a network of FO sensors to monitor strain during a slamming impact, and to test out a technique for signal processing. The strain measurements provided both peak strain data and served as a base for frequency analysis. The results showed that the FO strain sensors performed satisfactorily and were in general agreement with the conventional strain gauges used. The FO interrogation system was, however, not designed with sufficiently large dynamic range for the most extreme drop sequences. The peak strain in the panel was found to increase almost proportionally with the drop velocity, or drop height, and the wet fundamental frequency increased with increasing drop angle. Furthermore, the frequency decreased with increasing drop velocity.