The effect of microstructure and stress state on the fracture behaviour of wood

Boatright, S. W. J.; Garrett, G. G.

doi:10.1007/bf00555013

Cited by 45 publications

(24 citation statements)

References 15 publications

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“…Table II presents the statistical results (mean ± SD) for all variables during the 6 weeks of biodegradation. It should be noted that the fracture toughness of both undegraded materials are in agreement with literature values (Boatright and Garrett, 1983;Schniewind and Centeno, 1973). Indeed, the initial value of toughness was 38% higher for pine than for Douglas fir; whereas density was marginally lower for the pine samples.…”

Section: Resultssupporting

confidence: 91%

Crack propagation in biodegraded wood

Surini¹,

Chaplain²,

Castéra³

et al. 2010

Ann. For. Sci.

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Abstract• Fungal attack in wood involves severe mechanical losses, even in the early stages, due to depolymerisation of polysaccharides. The safety of building components could therefore be affected. It is believed that fracture properties could be much more sensitive to decay than conventionally measured properties, such as weight loss.• In this study, we propose the application of a fracture mechanics test, which measures the fracture toughness, K IC , during the biodegradation process. Two softwoods commonly used in construction, maritime pine and Douglas fir, were inoculated with Poria placenta. Samples were removed twice a week to determine the evolution of the decrease in their mechanical properties.• Toughness was initially greater for maritime pine, but a significant decrease of this property was observed during decay progression, while K IC remained more stable for Douglas fir. For maritime pine there was a loss of 52% of K IC , after 6 weeks of degradation. This species appears to be less durable even with respect to weight loss, which is less sensitive to decay than toughness.• This is a promising test for bio-damage quantification; however, due to the wood heterogeneity, measurement of the true impact of biodegradation is still difficult.

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Section: Resultssupporting

confidence: 91%

Crack propagation in biodegraded wood

Surini¹,

Chaplain²,

Castéra³

et al. 2010

Ann. For. Sci.

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“…Scanning electron microscopy of fracture surfaces has shown that the bridging behind the crack tip is a toughening mechanism in wood fracture which contributes to its nonlinear behavior . The alternation of earlywood and latewood fibers which have different microstructure, dimensions and stiffness can play an important role on the pattern of crack propagation (Boatright and Garrett 1983;Job and Navi 1996;Dill-Langer et al 2002).…”

Section: Introductionmentioning

confidence: 99%

Micromechanical approach to wood fracture by three-dimensional mixed lattice-continuum model at fiber level

Sedighi-Gilani

Navi

2007

Wood Sci Technol

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To investigate the fracture behavior of wood, the porosity and heterogeneities of its microstructure should be taken into account. Considering these features of wood microstructure in a continuum-based model is still a difficult problem and the lattice model might be an alternative. In the developed mixed lattice-continuum model, the probable crack propagation volume was modeled by defining a three-dimensional lattice of different beam elements and the other regions were considered as continuum medium. Different beam elements of lattice represented the earlywood fibers, latewood fibers, ray cells and bonding medium between the fibers. The proposed model was used to investigate the mechanism of mode I fracture in a small notched wood specimen in RL orientation. The resulting pre-peak and softening curve and also the crack opening trajectory in both cross-section and longitudinal-section in model were in good agreement with the experimental observations. This model shows the importance of considering the three-dimensional and distributed propagation of microcracks and main cracks in fracture stability. It was also shown that in mode I fracture, RL orientation, the main crack propagates in the earlywood ring.

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“…Most studies showed that a specimen size influence is less pronounced than in other materials like metals (Porter 1964, Boatright and Garrett 1983, Barrett 1976and Ewing and Williams 1979. Measuring the "strain energy release rate", G (which is proportional to K~ % for elastic behaviour) of western white pine in TL and RE direction with center notched plates and edge notched specimens (specimen length = 600 mm and width = 37.5 mm) Porter (1964) reports that no influence of the specimen thickness on G~c exists in the range of 3 to 25 mm.…”

Section: Introductionmentioning

confidence: 98%

“…It has been tried to apply linear fracture mechanics concepts on wood through non-linear elastic and anisotropic features are present. Based on early works of Schniewind (1962) and Porter (1964) on the critical energy release rate for unstable crack propagation, and on the work of Shi et al (1965) who derived crack-tip stress fields and stress intensity factors assuming rectilinear anisotropic bodies, many research work has been performed on influences of orientation, specimen shape, specimen size but also on other than geometrical parameters on fracturing of wood (Schniewind and Centeno 1973, Barrett 1976, Schniewind and Pozniak 1971, Barrett and Foschi 1977 Ewing and Williams 1979, Ebewele et al 198o, Schniewind et al 1982, Petterson and Bodig 1983, Boatright and Garrett 1983, Triboulet et al 1984, Cramer and McDonald 1989, Valentin and Adjanohoun 1992, Murphy 1979, BostrSm 1992.…”

Section: Introductionmentioning

confidence: 98%

“…Extensive measurements on the influence of specimen length and height on G~c showed similar independence of these parameters in a wide range of dimensions. Constant K~c were also obtained in four point bending tests on South African pine if the specimen thickness was larger than 5 mm (Boatright andGarrett 1983, Barrett 1976). On the other hand, influences of specimen thickness (3, 6, 12, 25, 50 mm) were found by Ewing and Williams (1979) in kiln dried Scots pine specimens, but these were obviously caused by residual stresses induced by the drying.…”

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

New splitting method for wood fracture characterization

Stanzl-Tschegg

Tan

Tschegg³

1995

Wood Sci.Technol.

101

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Summary A testing procedure with a new and simple specimen shape is presented which is appropriate to characterize fracturing of inhomogeneous and complex materials like wood. With this, the fracture energy of spruce wood is determined in the TL and RL direction. The "size effect", i.e. influences of specimen dimensions on K~c and Gf (specific fracture energy) are investigated. Stress and deformation distribution in the newly developed specimens are analysed with FE methods. The measured load-displacement curves are approximated by bilinear softening diagrams and FE analysis. Based on these results, it is tried to interpret typical deviations from LEFM's behaviour by mechanisms like microcracking, crack branching or crack tip bridging.

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The effect of microstructure and stress state on the fracture behaviour of wood

Cited by 45 publications

References 15 publications

Crack propagation in biodegraded wood

Crack propagation in biodegraded wood

Micromechanical approach to wood fracture by three-dimensional mixed lattice-continuum model at fiber level

New splitting method for wood fracture characterization

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