A study on fatigue crack propagation in thick composite adhesively bonded joints

International Journal of Fatigue

Lemanski

et al. 2019

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 processinduced 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.

Section: Fractographymentioning

confidence: 60%

Experimental and numerical study of process-induced defects and their effect on fatigue debonding in composite joints

International Journal of Fatigue

Lemanski

et al. 2019

“…For purpose of more efficiently investigating the mechanical behavior of adhesive bonded joints, several numerical simulations [11,12] and experimental analysis [13][14][15] have been conducted. Damage assessment of composite adhesion joints on experimental static and fatigue testing were carried out by Mattos et al [16].…”

Section: Introductionmentioning

confidence: 99%

Acoustic emission response and progressive failure behaviors of composite adhesively bonded joints loaded by Mode I and II

Shen

et al. 2019

Mater. Res. Express

The analysis of progressive failure process is one of the critical issues in the research of composite adhesive joints. In view of this point, acoustic emission (AE) is applied to real-time monitoring of the dynamic damage process of composite adhesive joints in some loading modes such as Mode I (double cantilever beam (DCB)) and Mode II (end notch flexures (ENF)). Furthermore, the high speed camera and scanning electron microscopy are carried to analyses the damage mechanisms of composite bonded joints. Results show that there are significant differences in the load-deflection curves of the specimens under the loads of Mode I and II. The main failure mode of the two types of loading modes is adhesion failure, and the accumulation of damage observed at the edge of the adhesively bonded layer cause defeat of the composite bonded joints. In addition, AE parameters including amplitude, hits, energy, and duration are connected with the fail mechanism. Furthermore, the dynamic characteristics of the AE signal, especially amplitude spectrum distribution, can provide evidences for studying progressive failure behaviors of composite adhesive joints.

“…Following the same method, Quaresimin et al [6] used the total SERR to evaluate the crack propagation phase for a composite single lap joint. Bernasconi et al [7] predicted the fatigue life based on the equivalent SERR of a composite single lap joint using the mode I crack growth rate law. Using the mode I crack growth rate data has been shown to predict the initial stage of the crack propagation, while the total SERR allowed for a more accurate prediction of the total fatigue crack growth life for a relatively thick composite joint (i.e.…”

Section: Introductionmentioning

confidence: 99%

A finite element study of fatigue crack propagation in single lap bonded joint with process-induced disbond

Lemanski

International Journal of Adhesion and Adhesives

et al. 2018

This paper presents a method for predicting fatigue crack propagation in adhesive bonded composite joints with an initial full-width disbond using finite element analysis and numerical integration of the material's fatigue crack growth rate law. Fatigue tests were conducted on single lap joints. Crack lengths were monitored from four runout corners. In-situ crack growth measurements were performed by ink injection to identify the crack front profile during fatigue loading. The crack growth was modelled using a fracture mechanics criterion considering two different crack propagation patterns. The material's fatigue crack growth rate law was determined experimentally using the standard double cantilever beam and end notch flexure specimens. Using the total strain energy release rate and the two crack scenarios, the numerical model predicted the lower and upper bounds of the measured fatigue crack growth rates of the lap joint.