Modeling & analysis of performance degradation of bolted composite lap geometries subjected to shock load

An analytical model and 3D finite element analysis (FEA) is completed to determine the effect of shock loading on vibration characteristics and stiffness of composite laminates. The bolted carbon composite lap geometry is prepared by varying number of bolts from 1 to 3 in a 500 mm width of plate. Analytically, it is a mass-spring based model where bolt(s), laminates and the clamped region are represented by a series of springs and masses. The obtained equations of motion contain information about geometrical parameters such as length, width, thickness and mass properties of composite plates. The frequency response acquired from mathematical model is compared and validated with FEA results acquired through ANSYS. Conclusions reveal that the main contributing factors to cause changes in stiffness and reduction in frequency are presence of bolts, increase in number of bolts and regions of stress concentration. Moreover, the acquired frequency response may act as a means of detecting changes in structural stiffness and the applied methodologies might be used to model larger mechanical and aerospace structures.