Predicting the longitudinal modulus of elasticity of Sitka spruce from cellulose orientation and abundance

Abstract

Sitka spruce (Picea sitchensis) is the most widely planted commercial tree species in the United Kingdom and Ireland. Because of the increasing use of this species for construction, the ability to predict wood stiffness is becoming more important. In this paper, a number of models are developed using data on cellulose abundance and orientation obtained from the SilviScan-3 system to predict the longitudinal modulus of elasticity (MOE) of small defect-free specimens. Longitudinal MOE was obtained from both bending tests and a sonic resonance technique. Overall, stronger relationships were found between the various measures of cellulose abundance and orientation and the dynamic MOE obtained from the sonic resonance measurements, rather than with the static MOE obtained from bending tests. There was only a moderate relationship between wood bulk density and dynamic MOE (R 2 s0.423), but this relationship was improved when density was divided by microfibril angle (R 2 s0.760). The best model for predicting both static and dynamic MOE involved the product of bulk density and the coefficient of variation in the azimuthal intensity profile (R 2 s0.725 and 0.862, respectively). The model parameters obtained for Sitka spruce differed from those obtained in earlier studies on Pinus radiata and Eucalyptus delegatensis, indicating that the model might require recalibration before it can be applied to different species.

Correlations among microfibril angle, density, modulus of elasticity, modulus of rupture and shrinkage in 6-year-old Eucalyptus urophylla × E. grandis

“…This parameter predicted the modulus of elasticity with a linear modeling better than MFA and density alone (non-linear trends). For example, McLean et al (2010) recently demonstrated that 76% of the variation in modulus of elasticity was explained by the factor ρ/MFA in wood samples of Picea. [24,40] for the intercept (R²=0.37, residual standard error = 12 MPa).…”

“…The methods of sampling preparation and measurement should be taken into account for comparing the relationships concerning the density, the microfibril angle, and the modulus of elasticity reported in the previous studies. For instance, Evans and Ilic (2001), Yang and Evans (2003) and McLean et al (2010) had employed the SilviScan device (Evans et al 1999) to perform multiple measurements to obtain a mean MFA across a small strip cut from the specimen. In this study, the microfibril orientation was not the main effect which explained the variability of modulus of elasticity and modulus of rupture.…”

Microfibril angle and density of hinoki (Chamaecyparis obtusa) trees in 15 half-sib families in a progeny test stand in Kyushu, Japan

“…In Douglas-fir (Pseudotsuga menziesii), density was the most contributor to MOE and MOR, and MFA was relatively unimportant [4]. In Sitka spruce (Picea sitchensis), both static and dynamic MOE were predicted by MFA and density (R 2 = 0.725 and 0.862 respectively) [5]. From these studies, it was assumed that also in hinoki, variation of mechanical properties would be explained by variation of MFA and density.…”

Modelling microfibril angle variation in New Zealand-grown radiata pine

“…The mechanical and physio-mechanical properties (mainly stiffness, shrinkage and stability) of wood are determined by the fundamental structure of its cells (Barnett and Bonham 2004;Cave 1969;Harris and Meylan 1965;McLean et al 2010;Wardrop and Preston 1947). Studies in radiata pine (Pinus radiata D. Don) and other softwood species have shown that the two most influential wood properties are basic density and the angle of the cellulose microfibrils (MFA) in the S2 layer of wood cell walls (Cown et al 1999;Donaldson 1997;Wagner et al 2012;Walker and Butterfield 1995;Walker 1996;Xu and Walker 2004).…”