Monte Carlo Simulation Methodology for the Reliability of Aircraft Structures

Aviation rules mandate the need for an aircraft structure to meet damage tolerance requirements. The damaged structure must maintain adequate residual strength in order to maintain its integrity and this is accomplished through a continuous inspection program. The multifold objective of this work is to present a methodology based on a direct Monte Carlo simulation (MCS) process to assess the reliability of an aircraft structure. Initially, the structure is modeled as a parallel system with active redundancy comprised of elements with uncorrelated strengths. Closed form expressions for the system capacity cumulative distribution function are expanded from three elements in the current literature up to six elements. The second objective is to compute the probability of failure of a fuselage skin lap joint under static load conditions by examining the residual strength of the fasteners when subjected to various load distributions initially and following subsequent fastener sequential failures. The last objective is to present a MCS methodology for computing the non-periodic inspections required in order to maintain a prescribed minimum reliability level.