Experimental and finite element studies of shock transmission through composite structures

Composite materials are more widely used today in engineering products than ever before. Shock transmission in jointed composite sections needs to be investigated to understand the affect of composite materials on the dynamic response of the system. There exists limited published work on transient shock propagation through composite sections. The aim of this study is to analyze the transient behavior of joints in composite materials subjected to low impact loads and to develop a computational model that provides an improved physics based shock model. The jointed connection will be investigated experimentally and using Finite Element Analysis (FEA). The bolted joint will be the type of connection investigated. This is a commonly used joint for composite assemblies. For simplicity a simple hat section and cantilever beam structure are chosen for investigation. The initial case study verifies the experimental and finite element results on the individual cantilever beam structure by comparing the accuracy of the finite element results of an aluminum cantilever beam to the composite cantilever beams. The second study investigates the composite bolted hat structure response to low impact shock loading. Two different composite lamina orientations were chosen, a 0/90 plain weave bidirectional composite and a 0° unidirectional composite. The structures are subjected to low impact loading (nondestructive) using a modally tuned impact hammer. Accelerations and impact force are recorded using an accelerometer and the modally tuned impact hammer respectively. A Normalized Root Mean Square Difference (NRMSD) criterion was used to compare the experimental results to the FEA results.