Methodology for residual strength of dynamically loaded composites

Abstract

In cooperation with the Aircraft Strength Research Institute of the Chinese Aeronautical Establishment (CAE) an analytical approach for modelling and calculation of the residual, strength of composites was developed during the past years in the Institute of Structural Mechanics. The main features of the approach are 1) an independent damage characterization method; 2) a new failure criterion for delamination damage; 3) a simple model for the prediction of impact damage, based on the bending strain energy density; and 4) an algorithm for the residual strength analysis of single and/or multiple delaminations, either introduced by impact or pre-implanted. The approach led to the development of a Windows compatible computer program, called "Composite Damage Tolerance Analysis Code (CDTAC)", which enables the calculation of the impact transient response, the impact damage and consequently the residual compressive strength of composite laminates, and, in an extended version, of stringer-stiffened composite panels. The comparison between calculated and experimentally evaluated impact damage zones as well as of the residual compressive strengths showed a good agreement of the results. In future work the extension of the program to the damage growth simulation under fatigue loading and the prediction of the residual strength after fatigue will be performed.