Dynamic Properties of Delaminated Braided Textile Composite Beams

In this paper, vibration analysis of through-width single- and multi-delaminated cantilevered composite beams is carried out using Finite Element Analysis (FEA) approach. Different configurations of multiple delaminations are considered. The FEA results for single delaminations are validated via experimental testing. It is found that changes in the natural frequencies of delaminated cantilevered beams are related to the number, type and distributions of delaminations within a beam. Also, the natural frequency shifts due to single or multiple delaminations are influenced by the thickness-wise locations of the delaminations. As the delamination is moved from the outermost inter-laminar layer towards the mid-plane of the beam, the natural frequency decreases and reaches a minimum value when the delamination is located at the midplane. Single delaminations have a more significant effect on natural frequencies than multiple delaminations of the same overall dimension as the single delamination. Furthermore, it is found that there is a greater reduction in natural frequency when multiple delaminations are close together than when they are spread out. However, where the locations of multiple delaminations coincide with nodal or antinodal vibration points, the effect is significantly altered.