Wood: a quasibrittle material R-curve behavior and peak load evaluation

Morel, Stéphane; Dourado, N.; Valentin, G.

doi:10.1007/s10704-004-7513-0

Cited by 86 publications

(57 citation statements)

References 17 publications

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“…In fact, the physical mechanism of fracture, such as crack bridging, emphasizes that LEFM cannot be directly applied to quasibrittle failures (Morel et al 2005). Although Irwin's modification includes a plastic energy term, there are still limitations for the energy balance approach in determining the conditions required for instability of an ideally sharp crack.…”

Section: R-curvementioning

confidence: 99%

“…The energy balance approach presents insuperable problems for many practical situations, especially for slow stable crack extension (Griffith 1920). Nevertheless, an adaptation of LEFM, referred to as an equivalent linear elastic approach (Morel et al 2005), can provide a useful approximation of the quasi-brittle behavior. On the basis of equivalent LEFM, the equivalent crack length is understood to be the crack length of the specimen which gives the same compliance as the real one.…”

Section: R-curvementioning

confidence: 99%

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Experimental Investigation of Mode-I Fracture Properties of Parallel Strand Bamboo Composite

et al. 2018

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Parallel stand bamboo (PSB) is a high-quality wood-like bamboo composite. Failure due to cracking is a major concern in the design of PSB components for building structures. The mode-I fracture properties of PSB composite were studied. The wedge splitting method was employed as the test approach. Numerical analyses were conducted to determine the appropriate test specimen dimensions so that valid fracture toughness could be obtained. An R-curve was evaluated in accordance with the equivalent linear elastic fracture mechanics (LEFM) theory. It was found that the initial crack depth ratio should be less than 0.4 for the fracture toughness test. The fracture toughness of PSB is higher than that of commonly used woods, and their fracture behavior is similar, exhibiting quasi-brittle behavior. The R-curve of the PSB exhibits rising behavior until the critical crack length is reached. However, the post-peak R-curve exhibits a descending behavior, contrary to that of quasi-brittle materials, which present a plateau in post-peak crack extension.

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Section: R-curvementioning

confidence: 99%

Section: R-curvementioning

confidence: 99%

Experimental Investigation of Mode-I Fracture Properties of Parallel Strand Bamboo Composite

et al. 2018

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“…Using the load-displacement curve to measure the work δW of the tensile machine during the span δt [19], one gets [20]. On the other hand, the driving force is estimated independently using the relation…”

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confidence: 99%

Depinning Transition in the Failure of Inhomogeneous Brittle Materials

Ponson

2009

Phys. Rev. Lett.

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The dynamics of a crack propagating in an elastic inhomogeneous material is investigated. The variations of the average crack velocity with the external loading are measured for a brittle rock and are shown to display two distinct regimes: Below a given threshold Gc, the crack velocity is well described by an exponential law v ≃ e − C G− Γ characteristic of subcritical propagation, while for larger values of the driving force G > Gc, the velocity evolves as a power law v ≃ (G − Gc) θ with θ = 0.80 ± 0.15. These results can be explained extending the continuum theory of Fracture Mechanics to disordered systems. In this description, the motion of a crack is analogue to the one of an elastic line driven in a random medium and critical failure occurs when the loading is sufficiently large to depinne the crack front from the heterogeneities of the material.PACS numbers: 62.20. Mk, 46.50.+a, 68.35.Ct Failure of inhomogeneous materials has been a very active field of research during the last decades (see Ref.[1] for a recent review). A great research effort in this field has been dedicated to the study of fluctuations: Fluctuations of velocity around the average motion of cracks when the studies were devoted to their highly intermittent dynamics [2,3,4,5], or variations to a straight trajectory when the works were dedicated to the rough geometry of fracture surfaces [6,7,8]. In both cases, these fluctuations were shown to display remarkably robust properties suggesting that crack propagation in disordered systems could be described on a general manner by relatively simple statistical models able to capture the competition between the two antagonist effects occurring during failure of inhomogeneous materials: Disorder and elasticity.Very recently, main statistical features of fluctuations of both trajectory and velocity for cracks propagating in brittle materials were captured by stochastic models of elastic lines driven in random media [9,10] that mimic the motion of cracks through the microstructural disorder of materials. However, the relevance of this theoretical framework for fracture problems is still a matter of debate: On the one hand, the ability of these models to describe the average behavior of the crack such as its mean velocity, or the critical external loading at failure, more interesting from a mechanical or an engineering point of view, is still an open question. On the other hand, a direct experimental observation of the critical dynamic transition from a crack pinned by the heterogeneities of the material (v = 0) to a propagating crack (v > 0), as predicted by this theory at the onset of material failure (driving force G = G c ), is still lacking. The investigation of this depinning transition on an experimental example is the central point of this Letter.The variations of the average crack velocity with the external driving force, i.e. the energy release rate G [11], are measured for a brittle rock. They are shown to exhibit two distinct regimes. Below a critical threshold G c , the crack velocity...

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“…Compliance can be calculated from a load-displacement curve (P-δ) [17,18], or from a load-crack opening displacement curve (P-COD) [19,20]. In the present study, we used the load-displacement curve.…”

Section: Measurement Of Crack Growthmentioning

confidence: 99%