V-NOTCHED COMPONENTS UNDER TORSIONAL FATIGUE LOADING [Keynote]

Finite Fracture Mechanics (FFM) is applied to assess the brittle or quasi-brittle failure initiation at sharp V-notches under torsional loading. By assuming that failure is shear stress governed, the approach is developed in the fatigue framework. The analysis includes a discussion on the calibration of the material properties, and the comparison with experimental data available in the literature.
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STUDY OF INTRA- AND INTER-LAMINAR DAMAGE INTERACTIONS IN LAMINATED COMPOSITES USING FINITE FRACTURE MECHANICS

Composite laminates are widely used in aerospace industry overall for their mass-to-performance ratio. In this context, the storage of cryogenic propellant is subject to numerous studies, in which the composite must ensure a sealing function. However, the permeability is strongly related to the damage state of the laminate and heterogeneities at micro and meso scales make their damage behavior hard to predict. Among all damage mechanisms, transverse cracks and microdelamination are particularly interesting. Indeed, their coalescence through the laminate thickness is likely to generate leakage paths. Experimental observations often show that the transverse cracking bifurcates either in microdelamination at ply interfaces or in additional transverse cracks in adjacent plies. The Finite Fracture Mechanics (FFM) demonstrated its relevance in the prediction of crack propagation but it relies on a presupposed path. In this context, two scenarios, microdelamination at transverse crack tips and transverse cracking in adjacent plies are studied with FFM in order to identify the preferred mechanism regarding some material properties (limit strength, energy release rate…) and geometrical parameters (thickness, orientation…). In addition to the cracking scenario and morphology, FFM will also provide information on cracking rates with the aim of predicting the overall damage state of the laminate.
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3D FINITE FRACTURE MECHANICS UNDER MODE I LOADING: THE FLAT ELLIPTICAL CRACK [Keynote]

In recent years, the Finite Fracture Mechanics approach, originally proposed by Leguillon in 2002, has been applied successfully to several material and geometrical configurations. However, up to now, most of the applications were restricted to two-dimensional geometries. In the present paper, we provide an insight to a simple yet challenging three-dimensional case, namely the flat elliptical crack. Results are provided in analytical form.
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ON THE DIFFICULTY OF IMPLEMENTING THE COUPLED CRITERION TO PREDICT GLASS FRACTURE [Keynote]

Glass is an extremely brittle material that behaves almost perfectly linear elastic until it fractures. The linear-elastic fracture mechanics (LEFM) approach described by Griffith’s energy criterion is typically used to explain failure from a pre-existing crack like defect. However, LEFM reaches its limits in explaining failure processes at general stress concentration points and implementing the Coupled Criterion (CC) to take over is a tricky task. This mainly because it requires the knowledge of the tensile strength of the material which is a parameter not easy to characterize in glass. It is in general defined through a statistical law and relies strongly with surface flaws. The general aim of this work is to give an overview of the current understanding of glass tensile strength.
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