Residual Strength Prediction for Aircraft Panels With Multiple Site Damage (MSD) Using the Elastic Plastic Finite Element Alternating Method (EPFEAM)

In this paper, a new analytical method for solving stable crack propagation problems in a ductile panel with a row of cracks, is presented. The main purpose of the present study is to estimate the maximum load carrying capacity of such panels accurately. The so called Elastic Plastic Finite Element Alternating Method (Pyo et al. (1994)) was extended to account for the propagating cracks. The crack propagation algorithm utilizes the analytic crack solution to release the stresses behind the growing crack tip. The Tε* integral is employed for the crack extension criterion. This integral parameter accounts for the near tip crack growth energy dissipation. The T* resistance curve for crack propagation can be extracted from the P-Δa curve of a single cracked specimen case via a generation phase analysis. The present method is applied for several problems for cracks growing in the fuselage skin of aging airplanes, in which a row of cracks develop (MSD; Multiple Site Damage) from rivet holes. The load capacity of such a damaged structure reduces by a considerable amount. If the applied stress exceeds the load carrying capacity, then a catastrophic failure occurs. In order to predict the behavior of such failures, one must account for plastic deformation since the material is ductile. Furthermore, the maximum load carried by the structure is often reached after some amount of crack propagation. In this paper, a series of analyses have been conducted and the predicted results compare favorably to experimental results.