Evaluation of bending strain measurements in a composite sailboat bowsprit with embedded fibre Bragg gratings

• Monitoring of strains by FBG sensors in advanced composite structures is critically considered.
• CFRP tensile specimens and a bowsprit tubular section are manufactured with embedded FBGs.
• Optical losses and Bragg spectra are investigated by means of OTDR and OLCR techniques.
• Embedded FBGs performances are evaluated during tensile and bending tests.

Acrylate-coated Fibre Bragg Gratings (FBGs) were embedded in a sailing boat bowsprit tubular section manufactured using the vacuum bagging process in autoclave with the aim of measuring strains under realistic loading conditions. In order to establish an effective procedure for sensor integration, flat tensile specimens with embedded sensors were firstly produced under different processing conditions, using advanced composite material employed in the marine industry. Information obtained in this way was used to manufacture a sailboat bowsprit with an array of gratings embedded between the last inner plies. In order to assess the sensitivity and accuracy of the embedded sensors, the bowsprit was subjected to bending tests and the results were compared to analytical values and to data obtained from electrical strain gages. Results are very encouraging but reveal that great attention must be paid both to the integration process and to the in situ calibration of the embedded sensors.