QUALITATIVE CHARACTERIZATION OF FATIGUE DAMAGE PROPAGATION IN LAMINATED CARBON FIBRE REINFORCED POLYMERS BY USING MICRO-COMPUTED TOMOGRAPHY

摘要

Whilst quality standards and damage tolerance techniques are unique for each industry, withinrnthe aircraft industry there is an overarching need to maintain flight safety. As the aircraft industryrncontinues to strive for improved fuel efficiency and reduced airframe weight there is growing usernof advanced laminated carbon fibre reinforced polymers (CFRP) in all types of structures.rnTherefore, it is essential to predict the future mechanical behaviour and service life of “flightrncritical structures” made from CFRP in such applications. Experimentally validated failurernsimulation models are not abundant in the literature for modern CFRP laminates and complexrnstructures. Neither is there abundant quantitative data capable of defining the characteristics ofrninitial microscopic damage evolution in such orthotropic laminates. Early prediction andrnmodelling of damage nucleation and subsequent evolution is thus precluded due to insufficientrnexperimental data. In this work, it is proposed to analyze the 3D microscopic damage behaviourrnobserved in CFRPs subjected to service-replicated (e.g. spectrum) fatigue loading. Probing thernevolution of the cracks and damage was performed using X-ray micro-computed tomographyrn(XR-microCT) which proved to be a reliable non-destructive testing (NDT) tool for qualitativelyrnvisualizing and monitoring damage mechanisms relative to the fatigue life. Findings may bernpotentially employed to develop and validate enrichment functions developed to span thernasymptotic fields at the crack-tip for implementation in X-FEM to simulate combined damagernmechanisms. The work described in this paper is the first step in a larger project tornquantitatively examine fatigue damage progression in advanced aerospace composites.