Probabilistic Approach to Damage Tolerance Design of Aircraft Composite Structures

Abstract

A probabilistic approach to determine design parameters for damage-tolerant composite aircraft structures has been developed. The main criterion for acceptance of a structure is a specified probability of failure. The development of this approach is motivated by the increasing use of damage-sensitive composite aircraft structures. The resulting probabilistic model takes into account a probabilistic assessment of in-service accumulated damage, the ability of non-destructive inspection methods to detect such damage, the residual strength degradation of damaged structure, quality of repair and loads/temperatures expected between damage initiation and detection/repair. The special attention has been paid to the availability of input probabilistic data and the possibility to obtain such data at reasonable cost. Computing tools and algorithms for the probabilistic analysis have been developed. The validity of the approach has been demonstrated on several existing structural components. The main result of the study is that the reliability of a damage-tolerable composite structure can be assessed on a quantitative basis, allowing aircraft manufacturers, operators and flight certification authorities to establish the maintenance service guidelines and estimate the reasonable inspection intervals. Engineers can use this methodology in the future as a guide to establish design and inspection criteria while considering structural risk and maintenance cost at the same. = probability of detecting a damage/defect with a size greater than a P f , POF = probability of failure S i = strength through i th interval T° = temperature, K t i = time interval

Inspection Intervals Optimization for Aircraft Composite Structures Considering Dent Damage

“…The inspection interval is preset as T, and the random time to detect the damage is expressed as t T × ξ, where ξ is the number of inspect times to detect the damage, which can be generated by a geometric distribution [14]. Assume that the jth damage occurs at t j , then it is detected at the ξth inspection after the damage, which can be expressed as t d j t j T ξ × T, where · is the floor operator.…”

“…Other research methodologies have been developed over the past decade, including case-based reasoning combined with rule-based reasoning by Liu et al [7]; modified analytical hierarchy process based on rough sets by Wu et al [8]; fuzzy group decision and information entropy by Cai and Zuo [9]; structural reliability assessment through first and second-order reliability method by Andrea and Ruediger [10]; reliability-based maintenance optimization by Wu et al [11,12]; "level of safety" for damage-tolerant aircraft structures by Cary and Kuen [13]; and risk analysis and probabilistic approaches by Lin and Styuart [14] and Styuart and Lin [15]. Also, several reports with probabilistic methodology development and certain database for composite structures can be regarded as valuable references [16][17][18][19].…”

Fatigue crack growth of multiple interacting cracks: Analytical models and experimental validation

“…In this way, millions of different configurations, corresponding to possible fatigue scenarios of the component under investigation, can be simulated to derive the probability of failure as a function of the number of loading cycles. In the field of fatigue design of military aircraft, the USAF has already taken into account the probabilistic methodology and requires a failure probability of less than 10 −7 per flight, although in some cases it has also adopted 10 −8 .…”

Reliability of Damage Tolerance Composite Structure Using Fasteners as Disbond Arrest Mechanism

“…However, impact damage and disbonds in composite structures are often caused by discrete events randomly, rendering traditional deterministic damage tolerance approach ineffective. To overcome this difficulty, a probabilistic approach to damage tolerance of composite structures has been developed by Lin and Styuart, et al [1][2][3] by taking into account the life-cycle discrete events of damage occurrence, peak load occurrence, as well as inspection and repair. The probabilistic method has been demonstrated to quantitatively assess the structural reliability and maintenance scheduling of an aircraft composite structure.…”