Scheduled maintenance optimization for aircraft composite structures considering uncertainty and structural health monitoring

Aircraft structural maintenance is one of the critical operational activities to guarantee continued airworthiness, which contributes a significant proportion of the total life-cycle cost. From a perspective of system engineering, a proper maintenance strategy developed in design phase is highly demanded. Currently, the Maintenance Steering Group-3 (MSG-3) document and deterministic methodologies are widely applied as guidance to make scheduled maintenance tasks. However, there are two fundamental shortcomings. First, the MSG-3 analysis largely relies on engineering experience without a consideration of various practical data, which is not suitable for new design aircraft without prototype. Secondly, they fail to cater for emerging technologies such as advanced composite structures and structural health monitoring.<br><br>The objective of the research is to determine flexible and cost-effective maintenance tasks for aircraft structures while maintaining an acceptable safety level. Two key parameters in scheduled maintenance, i.e. the inspection interval and the repair/replace threshold are addressed. Composite airframes are particularly investigated and damage characteristics are obtained. Considering the existence of uncertainty throughout aircraft life-cycle, non-deterministic methodologies are proposed to optimize maintenance tasks. Further, the integration of Structural Health Monitoring in scheduled maintenance is studied to examine the influence on safety as well as economy during an operational life-cycle.