In the present study, embedded Bragg grating sensors were arranged in a rosette configuration to simultaneously measure the in-plane strain components and the temperature change. The rosette consisted of four optical sensors. The sensors were embedded in neighbouring plies to realise a point-like measurement. Assuming linear thermoelastic behaviour, the relationship between the optical response from each sensor and the strains in the laminate was established. A finite element model was then used to quantify numerically the expected accuracy of the measured strain under various loading conditions.
The objective was to determine design changes that reduce the risk of damage in an embedded piezoceramic transducer. Finite element analyses were performed to calculate stresses in embedded piezoceramic transducers. The model consisted of elements representing the piezoceramic, the interconnectors and the conductive adhesive, and also included the cross-ply laminate. The parameters chosen in the study were the thickness of the interconnector, the material properties, as well as the length and thickness of the conductive adhesive. The stress state in the transducer was determined for different parameter combinations to find a design with low damage risk. For the parameters studied, the lowest risk for damage initiation was obtained for a transducer with a compliant adhesive was a small thickness, and an adhesive that covered the entire piezoceramic element from edge to edge. The strain at failure in the transducer was estimated, and the position for damage initiation in the transducer was determined. The findings from the finite element analysis were supported by the experimental results.