Comparison between static modulus of elasticity, non-destructive testing moduli of elasticity and stress-wave speed in white spruce and lodgepole pine wood

ABSTRACT

Static bending tests to measure modulus of elasticity (MOE_ST) or wood stiffness provide an indicator of the structural performance of a finished product. These tests are however, slow and expensive. Tests to measure MOE using non-destructive testing (NDT) provide alternatives to MOE_ST tests; however, relationships between the different modes of measurement need to be established. Non-destructive testing MOE measured by two methods (SilviScan [MOE_SS] and time of flight [MOE_TOF]) have been compared with MOE_ST for lodgepole pine and white spruce. The relationships between stress wave speed (SWS) and MOE_ST have also been evaluated. Simple linear regressions of MOE_SS, MOE_TOF, and SWS had greater explanatory power (higher coefficients of determination (R²)) than did multiple linear regressions including growth rate or other wood fibre attributes. Simple linear regression from MOE_TOF and MOE_SS on MOE_ST had lower R² for lodgepole pine than for white spruce; however, the converse was true for SWS. SWS had the highest R² (89%) and MOE_SS the lowest R² (47%) when regressed on MOE_ST in lodgepole pine. The results were tool and species specific, suggesting that R² between MOE_ST and non-destructive testing MOE values must be validated separately for each commercial tree species and for each measurement technique.

KEYWORDS:

• Mechanical properties of wood
• juvenile wood
• mature wood
• linear regressions
• ASTM-D-143

Acknowledgements

The authors thank the Canadian Wood Fibre Centre (CWFC) for funding under the Forest Innovation Program (FIP). They also acknowledge the work of Jared Salvail (CWFC) in carrying out the field work and that of William Belhadef (Université du Québec en Abitibi-Témiscamingue) in the static and TOF measurement of modulus of elasticity. The support of Sharon Meredith (Foothills Growth and Yield Association) was instrumental in carrying out this research. Comments on earlier versions of the manuscript by Isabelle Duchesne and two anonymous reviewers are greatly appreciated.

Disclosure statement

No potential conflict of interest was reported by the author(s).

Notes

1 Ross RJ, personal communication.