Fracture Mechanics Solutions for Interfacial Cracks between Compressible Thin Layers and Substrates

Abstract

The decohesion of coatings, thin films, or layers used to protect or strengthen technological and structural components causes the loss of their functions. In this paper, analytical, computational, and semi-analytical 2D solutions are derived for the energy release rate and mode-mixity phase angle of an edge-delamination crack between a thin layer and an infinitely deep substrate. The thin layer is subjected to general edge loading: axial and shear forces and bending moment. The solutions are presented in terms of elementary crack tip loads and apply to a wide range of material combinations, with a large mismatch of the elastic constants (isotropic materials with Dundurs’ parameters − 1 ≤ α ≤ 1 and − 0.4 ≤ β ≤ 0.4 ). Results show that for stiff layers over soft substrates ( α → 1 ), the effects of material compressibility are weak, and the assumption of substrate incompressibility is accurate; for other combinations, including soft layers over stiff substrates ( α → − 1 ), the effects may be relevant and problem specific. The solutions are applicable to edge- and buckling-delamination of thin layers bonded to thick substrates, to mixed-mode fracture characterization test methods, and as benchmark cases.

On delamination of bi‐layers composed by orthotropic materials: Exact analytical solutions for some particular cases

“…Numerical values of the functions involved in calculations are shown on Figures 2–4. In case of half‐plane, for large values of the following asymptotical expressions may be used [24] …”

“…Various particular configurations were studied by many researches [1–10, 14, 15, 18, 23–36]. Thus symmetrical splitting of layers was studied in [30, 31, 34] for isotropic, and in [2, 10, 25, 26, 28] for anisotropic cases.…”

“…The similar problem for a layer and a half‐plane of different materials were addressed in [32, 33]. Analytical solutions for particular cases of bilayers and layers on half‐planes of different material were obtained in [1, 3, 24]. Various configurations of both isotropic and anisotropic bilayers and layers on an elastic half‐plane were considered in [5–8, 14, 15, 18, 27, 29, 36].…”

A New Grating Thermography for Nondestructive Detection of Cracks in Coatings: Fundamental Principle

“…Therefore, these methods require a relatively long time to detect all the cracks in coatings. Currently, the detection of surface cracks in coatings is still a research hot spot in the nondestructive testing field [10][11][12][13][14][15][16].…”

“…When they meet cracks or defects, the interaction between the thermal wave and the crack generates a new thermal wave signal which will propagate to the surface. Then, the response signal can be detected by an infrared camera [12]. In this method the detector array can simultaneously detect multiple horizontal cracks.…”