Co-authors​ :

 Hao SU (ITALY), Monssef DRISSI-HABTI (FRANCE), Valter CARVELLI (ITALY) 

A new concept of dual-sinusoidal placement of distributed fibre-optic sensors has been proposed [1-3], where fibre-optic sensors are embedded within two plies of composite laminates. The so-constructed smart composite is well suited for fine structural health monitoring (SHM) of continuous fibre-reinforced polymer composite structures, expected to be used in offshore wind turbine blades. Despite existing research [1-3], smart composites with dual-sinusoidal placement of fibre-optic sensors are still seeking more simulation and testing of their mechanical and sensing behaviour under various loading conditions. Therefore, this work is devoted to studying the strain patterns resulting from a preliminarily optimized dual-sinusoidal placement of fibre-optic sensors under tension, bending, and torsion. In brief, through detailed finite element modelling of coupon-level composite specimens with embedded fibre-optic sensors, key parameters of embedment are identified and discussed first in terms of their influences on the mechanical behaviour of host composite structures. The responses of fibre-optic sensors under three quasi-static loading conditions are then analysed respectively to discuss what extra valuable mechanical information can be obtained from the novel placement strategy. The resulting strain distributions from all three quasi-static loading cases studied help illustrate the strain measuring advantages of dual-sinusoidal placement pattern compared to linear and single sinusoidal patterns. Moreover, for each loading condition, the simulated patterns obtained are of high coherence with the stress-strain field that each specimen experiences. Current work is a proof of concept that aims at identifying key parameters of embedment and how to refine them, as well as demonstrating the potential of dual-sinusoidal placement for multi-directional strain sensing and full monitoring coverage of increasingly larger composite structures. It is particularly beneficial to future applied scientific research on real large smart composite structures, such as for offshore applications, which will consider both numerical and validation steps to quantitatively strike a balance among mechanical influences, sensing functions, and monitoring coverage from the dual-sinusoidal placement of distributed fibre-optic sensors.