Forced Vibration Analysis And Optimization Of Moderately-Thick Fiber Steered Laminates With Embedded Gaps And Overlaps

Fiber placement is an automated manufacturing process that enables the steering of carbon fibers along preferable curvilinear paths. If optimized, steered fibers impregnated with epoxy resin can provide a significant improvement in the static and dynamic behaviour of a composite part. The manufacturing process, however, is far from being defect free. In particular, gaps and overlaps often appear during the placement of the fibers, with a resulting impact on the structural responses of the manufactured laminates. Such an impact on the variable stiffness properties has been recently assessed in literature for thin laminated structures. For fiber steered thick structural parts, however, the impact of gaps and overlaps is unknown. In addition, recently the use of Automated Fiber Placement (AFP) has been extended to manufacture moderately-thick composites, especially for applications as manned submersibles and wind turbine blades. This paper focuses on moderately-thick fiber steered laminated plates and aims at studying the role of shear deformation on forced vibration responses of fiber steered composite plates with embedded gaps and overlaps. To reduce the computational effort for the structural analysis, we use the equivalent single-layer method. In addition, to account for transverse shear stresses, we resort to third-order shear deformation theory, which assumes a quadratic distribution of transverse shear strain/stress through the thickness. Semi-analytic solutions are derived for the forced vibration analysis, using the hybrid Fourier-Galerkin method along with a numerical time integration technique. The effects of manufacturing parameters and transverse shear stresses are examined for a rectangular laminated plate under undamped vibration. Formulated in a multi-objective optimization framework, the optimum design of a variable stiffness plate is obtained to simultaneously maximize the vibration frequency response as well as the out-of-plane and in-plane stiffness.