The effect of growth-ring orientation on the compressive performance of Douglas fir

ABSTRACT

The effect of angle between growth-ring orientation and loading force on mechanical performance such as compressive strength, deformation and compression set-recovery of wood has not been fully understood. The specimens, with growth-ring orientations of 0° (G-0°, parallel to tangential direction), 15° (G-15°, angle between growth-ring and tangential direction) and 40° (G-40°), were compressed using a universal testing machine; meanwhile, strain distribution was recorded using digital image correlation (DIC). One specimen from each growth-ring orientation was scanned with X-ray computed tomography (X-ray CT) before and after compression test. Their micro-structure after compression test was imaged using a scanning electron microscope (SEM). The results show that compressive strength decreases and compression set-recovery increases as increasing the growth-ring orientation. In G-0° specimens, strain is easily accumulated in small regions in earlywood, resulting in structural compaction and collapse. The effect of latewood on compressive strength is small, resulting in a poor correlation between strain distribution and density profile. For G-40° specimens, strain is almost homogenously distributed in every layer of earlywood. Both earlywood and latewood restrain the specimen from deformation and failure. Hence, strain accumulates according to the ‘layers’ of earlywood. Strain distribution and structural changes in G-15° specimens were in between of G-0° and G-40° specimens.

KEYWORDS:

• Growth-ring orientation
• strain distribution
• structural changes

Disclosure statement

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

Additional information

Funding

This study was funded by Guangxi Key Laboratory of Superior Timber Trees Resource Cultivation (grant number 22-B-01-02) and the Research Project of Jiangxi Forestry Bureau [grant number 202135].