PSI - Issue 28

F.W. Panella et al. / Procedia Structural Integrity 28 (2020) 1709–1718 Author name / Structural Integrity Procedia 00 (2019) 000–000

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et al. (2017), Peng et al. (2015)). The growing interest for different damage types of Carbon Fibre Reinforced polymer (CFRP) composites involves the mechanism of fatigue damage, originated from porosities and small delaminations; numerous research studies examined delamination propagation resulting from opening or shear mode loads, as well as mechanical behaviour of wrinkle samples, defined as orientation variation of composite fibres in various dimensional scale, as demonstrated by Argüelles et al. (2010) and Liang et al. (2014). Wrinkle defect could arise during processes in which the composite is subjected to an incorrect layout of layers or thermal gradients and / or differential in pressures applied composite (Lightfoot et al. (2013) during process, Dattoma et al. (2018), Pandey and Sun (1999)), while delamination or plies separation represents the most common failure mode (mode I) in laminates (Argüelles et al. (2010)). The physical and mechanical behavior of composites have been intensely studied in presence of manufacturing or in-service damage for industrial requirements. In aerospace field, the growing application of composite materials requires a wide-ranging knowledge of mechanical behavior of CFRP under cyclic tensile or bending fatigue loads for design purposes with damage tolerance life predictions (Talreja (2003)). Since delamination initiation due to fatigue load and due to wrinkle defect’s presence are of hard detection (Garnier et al. (2011)), recent research shows possibility of combining different non-destructive approaches for a damage prediction based on suitable monitoring of fatigue damage evolution (Wang et al. (2020), Djabali et al. (2019)). The Infrared-thermographic technique with most accurate ultrasonic Phased Array (PA) method on CFRP parts represents a appropriate ND combination of techniques for a complete sub-superficial and in-depth control, as verified by authors and others (Dattoma et al. (2019), Dattoma et al. (2020), Galietti et al. (2015)). Since ultrasonic and IRT approaches are successfully employed (David-West et al. (2017), Garnier et al. (2011)), the superficial damage state that occurs due to fatigue phenomena requires a different inspection technique, therefore the authors employed the Digital Image correlation for the scope (Dattoma et al. (2019)).

Fig. 1. Overall research activities and scopes.

Temperature variation or ultrasonic signal amplitude perturbations during load (David-West et al. (2017)), together with displacement field anomalies, represent indirect parameter useful for a full-field study of fatigue degradation prediction, therefore NDT output parameters, stiffness variation and fatigue life reduction were correlated on different samples to evaluate damage evolution induced by fatigue tests and to give general indications on suitable data analysis to detect and follow material degradation for CFRP samples in presence of delamination initiation (Wang et al. (2020)). Following figure 1 shows a simplified block diagram, summarizing research methodology used in this work. IRT and