Mesoscale mechanics of wood cell walls under axial strain

Abstract

Trees and other woody plants are hierarchically structured to achieve a wide range of mechanical properties-necessary for their survival under various and varying loading conditions-with a narrow range of chemical composition. The hierarchical level understood to be directly responsible for modulating the longitudinal elastic modulus and yielding behavior is that of the composition of the cell walls, which consists of crystalline cellulose fibrils embedded in an amorphous matrix of hemicellulose and lignin. Here we report a simple coarse-grained model of the cellulose fibrils and hemicellulose chains to provide a bottom-up description of the mechanics. We identify the mechanical behaviors for varying fibril angles, plot force-strain relationships and compare the data with experimental results and theoretical predictions, providing insight into fundamental structure-property relations of wood. Our model shows that hemicellulose deforms in a stick-slip motion as the fibrils shear, resulting in permanent deformation without causing material damage, and leading to the characteristic softening of wood as deformation is increased. The main contribution of this work is the development of a model that can be fine-tuned and adapted to other applications. While it presents simple formulation, it can successfully describe several key phenomena, specifically the three regimes of mechanical behavior: elastic, plastic, and high-strain stiffening, as well as the dependence of modulus on the microfibril angle, and as such provides a bottom-up mechanistic approach to wood mechanics.

Effect of Silica Bodies on the Mechanical Behaviour of Oil Palm Empty Fruit Bunch Fibres

“…The anisotropic behaviour of the cell walls in lignocellulosic material (wood) has been investigated by Qing and Mishnaevsky (2009a) using a finite element model, whereas experimental work was performed by Burgert (2006). On the other hand, the cellulose-hemicellulose interface has recently been investigated numerically by Adler and Buehler (2013), where they suggested a stick-slip motion of the interface. In addition, Qing and Mishnaevsky (2009b) and Flores and Friswell (2012) modelled cellulose as a cylindrical material surrounded by lignin and hemicellulose.…”

“…However, it should be noted that pre-treatment of lignocellulosic fibres like OPEFB can cause degradation of the fibre components, namely cellulose, hemicellulose, and lignin (Isroi et al 2012). This we believe can cause significant damage to the fibres as the lignin and hemicellulose bind the cellulose fibrils together and provide structural integrity to the lignocellulosic fibres (Adler and Buehler 2013). Note that for OPEFB, it was reported that the composition of cellulose, hemicellulose, and lignin are 47.6%, 28.1%, and 13.1%, respectively Omar et al (2014).…”

Considering the possibility of bonding utilizing cold sintering for ceramic adhesives

“…In Figure 4A-G, the EDS mapping results show homogeneous chemical element distribution in the steel and CSCB. 43 Figure 8B showed the average peak flexure stress of E1, E2, and CSCB with adding 0, 10, and 13% glass fibers as function of temperature. The transition zone for the adhesion interface between the steel substrate and CSCB was about 15 nm, due mainly to the rough, inclined steel/CSCB interface.…”

“…43,44 The specimens were tested under a variety of loads at different annealing temperatures. 43,44 The specimens were tested under a variety of loads at different annealing temperatures.…”

Understanding Creep Behavior of Semicrystalline Polymer via Coarse‐Grained Modeling

“…In previous MD simulations of PP, the degree of polymerization indicating the number of monomers in a single chain is chosen to be 100, which leads to a chain contour length of around 30 nm . In the CG polymer model, the bond length between neighboring CG beads is selected as 1 nm, which is similar to those used in previous studies of the CG modeling of polymer materials, such as collagen, cellulose, hemicellulose, and epoxy . For the crystalline cellulose molecule, it consists of the un‐branched chains, which are formed by the covalently linked glucose molecules .…”