Design of experiments analysis of fundamental frequency of laminated composite hypar shells with cut-out

The effect of lamination angle (A), width-to-thickness ratio (B), cut-out location along x-direction (C) and cut-out location along y direction (D) on fundamental frequency of hypar shells made of laminated composites is considered using Taguchi robust design concept. Finite element analysis is done to obtain fundamental frequency of the structure for different parametric variation. Three levels of each parameter are considered to form L27 orthogonal array in order to maximize fundamental frequency. Main effect plot identifies the significant parameters. Optimal condition for maximum fundamental frequency is obtained as 45° lamination angle, width-to-thickness ratio of 20, cut-out location along x-direction 0.4 and along y-direction 0.3 (A2B1C3D2). Interaction plots locate the interaction effects between selected parameters. Analysis of Variance study evaluates the significant parameters and their contribution on output, i.e., fundamental frequency. Current investigation reveals, width-to-thickness ratio of shell is the most significant factor while lamination angle and cut-out location have little significance. Among the interacting parameters, interaction between lamination angle & cut-out location (A × C) and interaction between width-to-thickness ratio & cut-out location (B × C) have some significance. Width-to-thickness ratio (B) has 96.76% contribution while lamination angle (A) and cutout locations (C & D) and interactions have low contribution. Residual plots for fundamental frequency are considered and confirmation test validates the present analysis. S/N ratio is found to improve by 12.43% compared to the initial condition.