Material property identification in composite structures using time domain spectral elements

Abstract

Lightweight, highly optimized, aerospace structures like spacecraft, aircraft, and launch vehicles, are made up of composite structures. These composite structures as well as the additive manufacturing techniques used in recent times require material property identification. Also, one of the main concerns in composite structures is the degradation of the material properties due to aging of structure and moisture absorption. Identification of material properties of the degraded structure poses an important problem to determine the margins available for the safe performance of the structure. Here we propose a new method to identify the material property (like elastic properties and density estimation) nondestructively, in any general elastic structure with particular emphasis on composite structures. The proposed method requires few measured responses and a good numerical model to determine the material properties. The new procedure requires a simple input force on the structure at some known locations. This generates and propagates high-frequency stress waves in the structure. Very few measured responses are used, to compute the material properties. Time Domain Spectral Finite Element (TSFEM) is used as the numerical model since it has high convergence rates for high-frequency content transient loads. A new anisotropic Timoshenko composite time-domain spectral beam element is formulated for this purpose, which will be used to perform the material property identification for both metallic as well as composite structures. Measured responses are used in this numerical model which is coupled with, the nonlinear least square technique to get the material properties. The proposed approach is demonstrated using both numerically and experimentally obtained responses. These examples show the efficiency of the developed algorithm based on TSFEM in estimating the material property of a structure.