Structural Response of a Carbon Composite Wing using Fiber Bragg Gratings

摘要

The objective of this study is to obtain the structural response of a composite wing of an ultralight unmanned aerial vehicle using fiber Bragg grating (FBG) technology. The composite wing is instrumented with an optical fiber on its top and bottom surfaces positioned over the main spar, resulting in approximately 780 strain sensors bonded to the wings. The in-plane strains from the FBG sensors are used to obtain the out-of-plane loads as well as the wing shape at various load levels using NASA developed real-time load and displacement methods. In general, good agreement was achieved between the FBG strain sensors and conventional foil strain gages on a large-scale composite wing. Difference between direct measurements of loads and displacements was generally less than 4% of loads and displacements determined with FBG strain based methods. The composite wing is fabricated from laminated carbon uniaxial and biaxial prepreg fabric with foam-core sandwich skins and three spars with varying laminate ply patterns and wall thickness dimensions. From the fuselage centerline to the tip, the wing measures 5.5-m with a root chord dimension of 74-cm, and a maximum airfoil thickness of 10 centimeters. A three-tier whiffletree system is used to load the wing in a manner consistent with an in-flight loading condition.