Influence of morphology on the effective hygro-elastic properties of softwood (spruce) and hardwood (balsa)

Abstract

Wood materials are characterized by complex, hierarchical material structures spanning across various length scales. The present work aims at establishing a relation between the hygro-elastic properties at the mesoscopic cellular level and the effective material response at the macroscopic level, both for softwood (spruce) and hardwood (balsa). The particular aim is to explore the influence on the effective hygro-elastic properties under variations in the meso-scale morphology. The multi-scale framework applied for this purpose uses the method of asymptotic homogenization, which allows to accurately and efficiently obtain the effective response of heterogeneous materials characterized by complex meso-structural geometries. The meso-structural model considered for softwood is based on a periodic, two-dimensional statistically representative volume element that is generated by a spatial repetition of tracheid cells. The tracheid cells are modeled as hexagonal elements characterized by a certain geometrical irregularity. The hardwood meso-structure consists of a region composed of hexagonal cellular fibers with large vessels embedded, which is connected to a ray region that is constructed of ray cells. The hardwood fibers are modeled as hexagonal cellular elements, similar to softwood tracheids. The rays are represented by quadrilateral cells oriented along the radial direction, whereby different arrangements are considered, i.e., the ray cells are either regularly stacked or organized as a staggered configuration. The interface between the fiber and ray regions may also be characterized by a regular or a staggered arrangement. The meso-structural models for softwood and hardwood are discretized by means of plane-strain, finite element models, which describe the hygro-elastic response of the wood material in the radial–tangential plane. For softwood, the sensitivity of the effective elastic and hygro-expansive properties is explored as a function of the geometrical irregularity of the tracheids. For hardwood, the effective properties are studied under a variation of the ray cell arrangement, the type of interface between ray and fiber regions, and the vessel volume fraction. The modeling results agree well with results obtained from other numerical homogenization studies and show to be in reasonable agreement with experimental data taken from the literature.

Manufacturing of Fluff Pulp Using Different Pulp Sources and Bentonite on an Industrial Scale for Absorbent Hygienic Products

“…In general, the type of fiber in softwood and hardwood pulps is different. Softwood pulps contain tracheid cells and hardwood pulps contain fiber and vessel cells [ 34 ]. In fiber and vessel cells, the mechanism of water transfer occurs through cell openings, while water transfer in tracheid cells occurs through punctuations in the cell wall.…”

Study on the Fracture Toughness of Softwood and Hardwood Estimated by Boundary Effect Model

“…Thus, the microstructure of softwood is relatively simple. Although the mechanical properties of softwood have drawn some attention [ 12 , 13 , 14 , 15 ], there is limited research concerning the influence of the growth ring on the fracture behavior of softwood. In contrast, hardwoods normally present a more complex structure with different types of cells.…”

Multifield nested metafilters for wave propagation control

“…From the solution of the cell problems, the effective material properties are obtained, together with the local microstructural displacement, strain and stress fields. The method is thus appealing for a broad range of applications, including thermo-mechanical [60][61][62], thermo-diffusive [63] and elastodiffusive [64], thermo-piezoelectric [65][66][67], hygro-mechanical [68][69][70], and chemo-diffusive-mechanical [71] problems. By applying a bilateral Laplace transform in time [72] to governing equations at the microscale, the effective response of the microstructured layer considered in this communication will be determined as a function of the tuning parameter of the piezoelectric phase, while simultaneously accounting for the frequencydependency of the properties of the viscoelastic constituent.…”