Experimental and numerical study of process-induced defects and their effect on fatigue debonding in composite joints. (August 2019)

• Record Type: Journal Article
• Authors: Liu, Yiding; Zhang, Xiang; Lemanski, Stuart; Nezhad, Hamed Yazdani; Ayre, David
• Is Part Of: International journal of fatigue. Volume 125(2019)
• Page Start: 47
• Page End: 57
• Publication Date: 2019-08
• Subjects: Adhesive bonding -- Disbond -- Composites -- Finite element analysis -- Fatigue life prediction; Materials -- Fatigue -- Periodicals; Materials -- Fatigue; Periodicals; 620.1122
• DOI: 10.1016/j.ijfatigue.2019.03.033
• Languages: English
• ISSNs: 0142-1123

Abstract

Highlights: Bonded joint contained either cohesive or adhesive disbond damage representing defects or accidental damage. Fatigue debonding was investigated by experiment and modelling. A normalised strain energy release rate established a master curve of the material's fatigue debonding growth rate. Using the master curve and calculated debonding driving force, predicted fatigue life covered the upper and lower bounds of tests. Abstract: Laboratory coupon joints for fatigue debonding tests usually have narrow width and a through-width initial disbond. However, realistic structural joints are much wider and may contain process-induced defects and accidental damage; both are much smaller than the joint width. Small and discrete damage may behave differently from the idealised through-width disbond crack. This has brought a question on whether the laboratory coupon joint can accurately represent the fatigue behaviour of wider structural joints. This paper presents an experimental and numerical study of fatigue behaviour of a wide bonded lap joint with a process-induced defect of semi-circular shape. Fatigue debonding propagation was monitored by ultrasound inspection. Fatigue life was predicted using a normalised strain energy release rate parameter calculated by finite element method, and the adhesive material fatigue crack growth rate data measured under single and mixed mode conditions. Simulation of process-induced defect and validation by experiments have brought a better understanding of fatigue debonding behaviour in wide joints containing realistic damage. Suggestions are given for fatigue fracture tests of bonded joints.