Design of Health and Usage Monitoring Systems Based on Optical Fibers for Composite Wing Spars

Health and usage monitoring systems may have a key role in the definition of new strategies for the design and maintenance of modern aerospace composite structures. Design of composite components is notoriously affected by damage tolerance considerations, since accidents occurring during production processes, as well as in-service exogenous events may induce barely visible damages. At first, this paper describes the most viable general techniques for integrating optical fibre sensors into composite materials. Then the design of a specific strain sensing systems to be integrated into composite spars of a wing-box is presented, aimed to exploit the load and damage monitoring features offered by such type of sensors. Finally, the capability of detecting delaminations inside the caps of a composite spar through OF-based monitoring systems is discussed. Numerical techniques are adopted for studying the influence exerted by delaminations on the strain fields in a composite element. As a benchmark, a C-shaped composite spar is chosen, characterized by different thicknesses and stacking sequences