Crack Initiation From Homogeneous and Bimaterial Corners

Grenestedt, Joakim L; Hallström, Stefan

doi:10.1115/1.2788986

Cited by 29 publications

(7 citation statements)

References 17 publications

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“…The small-scale interfacial cracking problem for a crack originating at an interface corner is completely analogous to the small-scale yielding problem of traditional fracture mechanics [33,59]. The small-scale interfacial cracking problem for a crack originating at an interface corner is completely analogous to the small-scale yielding problem of traditional fracture mechanics [33,59].…”

Section: Small-scale Crackingmentioning

confidence: 98%

Strength of butt and sharp-cornered joints

Reedy¹,

David²

2002

Adhesion Science and Engineering

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Section: Small-scale Crackingmentioning

confidence: 98%

Strength of butt and sharp-cornered joints

Reedy¹,

David²

2002

Adhesion Science and Engineering

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“…Furthermore, at the large size limit, the size of singular stress field is much larger compared to the length of the equivalent crack, which implies that the only relevant length scale involved is the length of the equivalent crack. Based on the dimensional analysis, K and H k can be related as (Grenestedt and Hallstrom 1997;Liu and Fleck 1999;Dunn et al 2001;Labossiere et al 2002): where constants a 1 and a 2 = dimensionless complex numbers, which can be calculated by solving an auxiliary small-scale cracking problem (Akisanya and Fleck 1997;Grenestedt and Hallstrom 1997;Liu and Fleck 1999;Labossiere et al 2002;Le et al 2010) (Fig. 2, right).…”

Section: Scaling Of Strength Of Bimaterials Structures With Strong Strmentioning

confidence: 99%

General size effect on strength of bimaterial quasibrittle structures

2011

Int J Fract

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This paper presents a general size effect equation for the strength of hybrid structures, which are made of two dissimilar quasibrittle materials with a thin and weak bimaterial interface. Depending on the material mismatch and structure geometry, a singular stress field could occur at the bimaterial corner. For structures with strong stress singularities, an energetic size effect is derived based on the equivalent linear elastic fracture mechanics and asymptotic matching. For structures without stress singularities, a finite weakest link model is adopted to derive the size effect. A general scaling equation that bridges the limits of strong and zero stress singularities is formulated by combining the energetic scaling of fracture of the bimaterial corner and the finite weakest link model.

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“…where £ = effective modulus of composites or steel, = geometry-dependent constant which can be determined by solving an auxiliary small-scale cracking problem [2,3,8,13,14]; Gf = fracture energy and Cf = length of the fully developed FPZ. Evidently, without knowing c/, the fracture energy Gf cannot be identified by fitting size effect data with Eq.…”

Section: Fig 4 Curves Of Load Versus Relative Displacement (Measuredmentioning

confidence: 99%

Scaling of Strength of Metal-Composite Joints—Part III: Numerical Simulation

Bažant

2013

Journal of Applied Mechanics

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The size effect in the failure of a hybrid adhesive joint of a metal with a fiber-polymer composite, which has been experimentally demonstrated and analytically formulated in preceding two papers, is here investigated numerically. Cohesive finite elements with a mixed-mode ß-acture criterion are adopted to model the adhesive layer in the metal-composite interface. A linear tractionseparation softening law is assumed to describe the damage evolution at debonding in the adhesive layer. The results of simulations agree with the previously measured load-displacement curves of geometrically similar hybrid joints of various sizes, with the size ratio of 1:4:12. The effective size of the fracture process zone is identified from the numerically simulated cohesive stress profile at the peak load. The fracture energy previously identified analytically by fitting the e.xperimentally observed size effect cwves agrees well with the fracture energy of the cohesive crack model obtained numerically by optimal fitting of the test data. ] metal-composite joints. For a double-lap joint of steel and fiberpolymer composite analyzed and tested at Northwestern University (see Fig. 1 (test series 2 in Ref.[1])), the dominant stress singularity exponent was found to be A = -0.459 -I-0.06/ (/' = \f^) for the inner corners and / = -0.219 for the outer comers [2]. Since the stress singularity at the inner comer of the joint is stronger than at the outer one, a crack will emanate from the inner corner and propagate along the weakest plane in the bimaterial joint. This plane of propagation will lie either in the metal-composite interface or in the fiber composite.Although the stress singularity exponent at the inner comers is very close to the exponent of -1/2 at the crack tips, the analysis of fracture at the bimaterial corner is complicated by the fact that the elastic energy release rate corresponding to a singularity exponent > -1/2 is zero. As such, the energetic argument of linear elastic fracture mechanics (LEFM) cannot directly be used to characterize the crack initiation from the comer. Rather, one must take into account the development of a finite fracture process zone (FPZ) at the inner comer, which can be quite large when dealing with a quasi-brittle material such as fiber composite [2,3]. For a propagating crack, the size of the FPZ is approximately constant, a material characteristic. The consequence is a size effect on the strength of the metal-composite joints.The size dependence of the nominal strength of hybrid joints has been studied experimentally and theoretically in the preceding papers [1,2]. For example, when the strength values measured in test series 2 of Ref.[1] are plotted in a logarithmic scale, the nominal strengths of geometrically similar metal-c.omposite joints are seen to decrease with the joint size as seen in Fig. 2.It was found that the size dependence of joint strength can be expressed by a formula similar to the classical type 2 size effect law [4][5][6][7] that has been shown to apply to homogeneous qua...

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Crack Initiation From Homogeneous and Bimaterial Corners

Cited by 29 publications

References 17 publications

Strength of butt and sharp-cornered joints

Strength of butt and sharp-cornered joints

General size effect on strength of bimaterial quasibrittle structures

Scaling of Strength of Metal-Composite Joints—Part III: Numerical Simulation

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