Strain Measurements of a Sailboat Bowsprit Cured in Autoclave by Means of Embedded Fibre Bragg Gratings

Acrylate-coated Fibre Bragg Gratings (FBGs) were embedded in a sailing boat bowsprit tubular section manufactured using vacuum bagging process in autoclave with the aim of reliably measuring strains under realistic loading conditions. In order to establish an efficient integration procedure, flat tensile specimens with embedded acrylate-coated fibres and FBGs were firstly produced under different processing conditions, using advanced composite material employed in the maritime industry. Optical losses and performance of the sensors embedded in the specimens were evaluated using Optical Time Domain Reflectometry and through comparison with standard electrical strain gages. Information obtained in this way was then used for the production of a sailboat bowsprit with a rectangular hollow section and an array of gratings embedded between the inner last plies. In order to assess the quality of the optical fibre sensors results, the bowsprit was subjected to bending tests and the measured strain values were compared to the analytical data and the experimental measurements obtained from electrical strain gages. Results are very encouraging but reveal that great attention must be devoted to the integration process and especially the in-situ calibration of the FBG sensors.