Micromechanical modeling of solid-type and plate-type deformation patterns within softwood materials. A review and an improved approach
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Karin Hofstetter
Abstract
Wood exhibits a highly diverse microstructure. It appears as a solid-type composite material at a length scale of some micrometers, while it resembles an assembly of plate-like elements arranged in a honeycomb fashion at the length scale of some hundreds of micrometers. These structural features result in different load-carrying mechanisms at different observation scales and under different loading conditions. In this paper, we elucidate the main load-carrying mechanisms by means of a micromechanical model for softwood materials. Representing remarkable progress with respect to earlier models reported in the literature, this model is valid across various species. The model is based on tissue-independent stiffness properties of cellulose, lignin, hemicellulose, and water obtained from direct testing and lattice-dynamics analyses. Sample-specific characteristics are considered in terms of porosity and the contents of cellulose, lignin, hemicelluloses and water, which are obtained from mass density measurements, environmental scanning micrographs, analytical chemistry, and NMR spectroscopy. The model comprises three homogenization steps, two based on continuum micromechanics and one on the unit cell method. The latter represents plate-like bending and shear of the cell walls due to transverse shear loading and axial straining in the tangential stem direction. Accurate representation of these deformation modes results in accurate (orthotropic) stiffness estimates across a variety of softwood species. These stiffness predictions deviate, on average, by less than 10% from corresponding experimental results obtained from ultrasonic or quasi-static testing. Thus, the proposed model can reliably predict microscopic and macroscopic mechanical properties from internal structure and composition, and is therefore expected to significantly support wood production technology (such as drying techniques) and mechanical analyses of timber structures.
©2007 by Walter de Gruyter Berlin New York
Articles in the same Issue
- Meetings
- Micromechanical modeling of solid-type and plate-type deformation patterns within softwood materials. A review and an improved approach
- Failure mechanisms in wood-based materials: A review of discrete, continuum, and hybrid finite-element representations
- Morphological lattice models for the simulation of softwood failure and fracture
- Experimental and numerical investigation of wood fracture mechanisms at different humidity levels
- Material point method simulations of transverse fracture in wood with realistic morphologies
- Simulation of cracks in wood using a coupled material model for interface elements
- Preliminary tests to evaluate the mechanical properties of young trees with small diameter
- Characterization and strength modeling of parallel-strand lumber
- Dynamic behaviour of cork and cork-filled aluminium tubes: Numerical simulation and innovative applications
- A numerical study of the transverse modulus of wood as a function of grain orientation and properties
- Effects of ring characteristics on the compressive strength and dynamic modulus of elasticity of seven softwood species
- Experimental device for the accurate determination of wood-water relations on micro-samples
- Evaluating the suitability of hybrid poplar clones for the manufacture of oriented strand boards
- Finely milled kenaf core as a natural plywood binder
- Alkaline peroxide treatment of ECF bleached softwood kraft pulps. Part 1. Characterizing the effect of alkaline peroxide treatment on carboxyl groups of fibers
- Alkaline peroxide treatment of ECF bleached softwood kraft pulps: Part 2. Effect of increased fiber charge on refining, wet-end application, and hornification
- Molar mass determination of lignins by size-exclusion chromatography: towards standardisation of the method
Articles in the same Issue
- Meetings
- Micromechanical modeling of solid-type and plate-type deformation patterns within softwood materials. A review and an improved approach
- Failure mechanisms in wood-based materials: A review of discrete, continuum, and hybrid finite-element representations
- Morphological lattice models for the simulation of softwood failure and fracture
- Experimental and numerical investigation of wood fracture mechanisms at different humidity levels
- Material point method simulations of transverse fracture in wood with realistic morphologies
- Simulation of cracks in wood using a coupled material model for interface elements
- Preliminary tests to evaluate the mechanical properties of young trees with small diameter
- Characterization and strength modeling of parallel-strand lumber
- Dynamic behaviour of cork and cork-filled aluminium tubes: Numerical simulation and innovative applications
- A numerical study of the transverse modulus of wood as a function of grain orientation and properties
- Effects of ring characteristics on the compressive strength and dynamic modulus of elasticity of seven softwood species
- Experimental device for the accurate determination of wood-water relations on micro-samples
- Evaluating the suitability of hybrid poplar clones for the manufacture of oriented strand boards
- Finely milled kenaf core as a natural plywood binder
- Alkaline peroxide treatment of ECF bleached softwood kraft pulps. Part 1. Characterizing the effect of alkaline peroxide treatment on carboxyl groups of fibers
- Alkaline peroxide treatment of ECF bleached softwood kraft pulps: Part 2. Effect of increased fiber charge on refining, wet-end application, and hornification
- Molar mass determination of lignins by size-exclusion chromatography: towards standardisation of the method
