Development and experimental validation of a continuum micromechanics model for the elasticity of wood

Hofstetter, Karin; Hellmich, Christian; Eberhardsteiner, Josef

doi:10.1016/j.euromechsol.2005.05.006

Cited by 206 publications

(138 citation statements)

References 40 publications

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“…The composition of wood is inhomogeneous, and the spatial distribution of the different cell types (and their size) may vary, thus the physical properties of wood observed at the macroscopic level vary signifi cantly even within the same species (Keunecke et al 2008). This is a reason why the simulations of the mechanical behavior of wood are diffi cult (Hofstetter et al 2005 ). The improved knowledge of structure-property relationships down to the cellular level combined with imaging methods would probably facilitate this situation.…”

Section: Introductionmentioning

confidence: 99%

Synchrotron-based tomographic microscopy (SbTM) of wood: development of a testing device and observation of plastic deformation of uniaxially compressed Norway spruce samples

et al. 2012

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To understand better the structure-property relationships of wood in situ, nondestructive synchrotron-based tomographic microscopy (SbTM) with subcellular resolution is useful. In this context, an in situ testing device was developed to determine the cellular response of wood to mechanical loading. Different rotationally symmetric specimens were tested to synchronize the failure areas to the given scanning areas. Norway spruce samples were uniaxially compressed in the longitudinal direction and scanned in situ at several increasing relative forces ending up in the plastic deformation regime. A suffi ciently high quality in situ tomography was demonstrated. The reconstructed data allowed the observation of the load-dependent development of failure regions: cracks and buckling on the microstructure were clearly visible. Future investigations with SbTM on different wood species, loading directions, and different moisture contents are promising in terms of the micromechanical behavior of wood.

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Section: Introductionmentioning

confidence: 99%

Synchrotron-based tomographic microscopy (SbTM) of wood: development of a testing device and observation of plastic deformation of uniaxially compressed Norway spruce samples

et al. 2012

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“…In the line of Popper, who stated that a theory-as long as it has not been falsified-will be 'the more satisfactory the greater the severity of independent tests it survives' (cited from Mayr 1997, p. 49), the verification of the micromechanical representation of HA biomaterials (equations (3.1)-(3.5) for elasticity, and equations (3.6)-(3.12) for strength) will rest on two independent experimental sets, as has been successfully done for other material classes such as bone (Hellmich & Ulm 2002;Hellmich et al 2004; or wood (Hofstetter et al 2005(Hofstetter et al , 2006. Biomaterial-specific macroscopic (homogenized) stiffnesses C poly (Young's moduli E poly and Poisson's ratios n poly ), and uniaxial (tensile and compressive) strengths (S ult,t poly and S ult,c poly ), predicted by the micromechanics model (3.1)-(3.12) on the basis of biomaterial-independent (universal) elastic and strength properties of pure HA (experimental set I, table 2) for biomaterial-specific porosities f (experimental set IIa, tables 3 and 4), are compared with corresponding biomaterial-specific experimentally determined moduli E exp and Poisson's ratios n exp (experimental set IIb-1, table 3) and uniaxial tensile/compressive strength values (experimental set IIb-2, table 4).…”

Section: Model Validation (A) Strategy For Model Validation Through Imentioning

confidence: 99%

The role of disc-type crystal shape for micromechanical predictions of elasticity and strength of hydroxyapatite biomaterials

Fritsch

Hellmich

Dormieux

2010

Phil. Trans. R. Soc. A.

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The successful design of ceramic bone biomaterials is challenged by two competing requirements: on the one hand, such materials need to be stiff and strong, which would suggest a low porosity (of pore sizes in the 10-100 mm range) to be targeted; on the other hand, bone biomaterials need to be bioactive (in particular vascularized), which suggests a high porosity of such materials. Conclusively, reliable information on how porosity drives the stiffness and strength properties of ceramic bone biomaterials (tissue engineering scaffolds) is of great interest. In this context, mathematical models are increasingly being introduced into the field. Recently, self-consistent continuum micromechanics formulations have turned out as expressedly efficient and reliable tools to predict hydroxyapatite biomaterials' stiffness and strength, as a function of the biomaterialspecific porosity, and of the 'universal' properties of the individual hydroxyapatite crystals: their stiffness, strength and shape. However, the precise crystal shape can be suitably approximated by specific ellipsoidal shapes: while it was shown earlier that spherical shapes do not lead to satisfactory results, and that acicular shapes are an appropriate choice, we here concentrate on disc-type crystal shape as, besides needles, plates are often reported in micrographs of hydroxyapatite biomaterials. Discbased model predictions of a substantial set of experimental data on stiffness and strength of hydroxyapatite biomaterials almost attain the quality of the very satisfactory needle-based models. This suggests that, as long as the crystal shape is clearly nonspherical, its precise shape is of secondary importance if stiffness and strength of hydroxyapatite biomaterials are predicted on the basis of continuum micromechanics, from their micromorphology and porosity.

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“…A notable correlation can be observed between the two stiffness profile parameters and mass density and moisture content measurements. The reason for this observation lies in the micromechanical model (Hofstetter et al 2005) which was employed for computing the clearwood stiffness tensor within Kandler et al (2015). For the micromechanical model, mass density and moisture content are the two main input parameters.…”

Section: Statistical Evaluation Of the Datamentioning

confidence: 99%

Experimental study on glued laminated timber beams with well-known knot morphology

2018

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Nowadays, the impact of knots on the failure behaviour of glued laminated timber (GLT) beams is considered by subjecting the single lamellas to a strength grading process, where, i.a., tracheid effect-based laser scanning is used to obtain information about knot properties. This approach single-handedly defines the beam's final strength properties according to current standards. At the same time, advanced production processes of such beams would allow an easy tracking of a scanned board's location, but, at this point, previously obtained detailed information is already disregarded. Therefore, the scanning data is used to virtually reconstruct knot geometries and group them into sections within GLT beams. For this study, a sample of 50 GLT beams of five different configuration types was produced and tested under static four-point-bending until failure. As for each assembled lamella the orientation and position within the corresponding GLT beam is known, several parameters derived from the reconstructed knots can be correlated to effective GLT properties. Furthermore, the crack patterns of the tested beams are manually recorded and used to obtain measures of cracks. A detailed analysis of the generated data and their statistical evaluation show that, in the future, dedicated mechanical models for such timber elements must be developed to realistically predict their strength properties. A potential approach, using fluctuating section-wise effective material properties, is proposed.

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Development and experimental validation of a continuum micromechanics model for the elasticity of wood

Cited by 206 publications

References 40 publications

Synchrotron-based tomographic microscopy (SbTM) of wood: development of a testing device and observation of plastic deformation of uniaxially compressed Norway spruce samples

Synchrotron-based tomographic microscopy (SbTM) of wood: development of a testing device and observation of plastic deformation of uniaxially compressed Norway spruce samples

The role of disc-type crystal shape for micromechanical predictions of elasticity and strength of hydroxyapatite biomaterials

Experimental study on glued laminated timber beams with well-known knot morphology

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