Fatigue behavior of [0n/90n]s composite cantilever beam under tip impulse loading

Vibration induced fatigue analysis of cross-ply [0n/90n]s cantilever beam under tip impulse loading is presented. As a first step, vibration induced stress for the given tip impulse loading was evaluated using modal analysis. Viscous damping model was used for evaluating the stress state as a function of time. The stress-time history was converted into block loading consisting of many sub-blocks. The block loading consisted of four sub-blocks and a total of 135 numbers of cycles. The block loading was repeated after certain time duration. Further, fatigue analysis was performed based on the block loading condition evaluated. Fatigue failure initiation was examined using S–N curve based approach, residual strength approach as well as failure function approach. Number of blocks to failure initiation and the location of failure were obtained. Analysis of cross-ply [0n/90n]s cantilever beam under tip static loading was also conducted for comparison. Studies are also presented using 3D finite element analysis (FEA). Number of blocks required to cause fatigue failure initiation under tip impulse loading was found to be 332 and 331 using the analytical method and 3D FEA, respectively for the geometry of the beam, material properties and loading condition considered.