Shape and Layer Optimization for the Dynamic Characterization of Carbon Fiber Plastics

Abstract

A method is proposed for determining the optimum size and layer structure of dynamic test specimens made of carbon fiber reinforced plastics for shaker testing. In order to simulate the fatigue strength of high performance structures, detailed knowledge of their dynamic material properties is required. The quality of the test specimens is mainly influenced by their shape and, in case of carbon fiber materials, by their layer structure and fiber orientation. The design goals of the optimization are to increase test accuracy and to reduce testing time. While the accuracy increases with higher amplitudes and equal stress distribution in the specimen, the time efficiency decreases with higher amplitudes. Especially with the introduced method, dynamic testing provides highly accurate results and can be used to validate the stiffness parameters which are mostly derived from static testing. The natural frequencies for a given shape depend only on the material stiffness parameters and the material density. Using classical laminate theory, the stiffness parameters are optimized in a best-fit approach and can thus be used to minimize the error of measurement of the static material characterization.