Natural frequency shifts and mode shapes in delaminated textile composite beams

Using numerical method, this work investigates the effect of delamination on the dynamic properties of fibre-reinforced composite laminates. Delaminated regions within the composite were created along the axial and transverse directions of beam FE model and numerical investigations were carried out using the finite element (FE) method. The Abaqus FE code was used to simulate the natural frequencies of the beams. It was found for the model used in this work that a delaminated length of 25 mm was the minimum delaminated length for acceptable level of delamination. Delamination in the mid-plane of the cross-section significantly affects natural frequency, while the adverse effect of delamination on natural frequency decreases progressively as the delamination moves towards the outer interlaminar layers. The effect of axial location of delamination on the natural frequency depends on whether the delamination coincides with a nodal or anti-nodal position of a vibrating beam. The material properties used in this simulation were determined experimentally; furthermore the numerical results showed good agreement with the experimental results.