The Impact of Earlywood and Latewood on the Compressive Stress of Thermally Modified Douglas Fir
Thermal modification can increase the physical stability and impact the mechanical strength of wood. It is necessary to understand the effects of modifications on the compressive stress of wood. In this study, Douglas fir (<i>Pseudotsuga menziessi</i>) blocks were modified at 180 °C (TM-...
| Main Authors: | , , , , , |
|---|---|
| Format: | Article |
| Language: | English |
| Published: |
MDPI AG
2023-07-01
|
| Series: | Forests |
| Subjects: | |
| Online Access: | https://www.mdpi.com/1999-4907/14/7/1376 |
| _version_ | 1797589242117881856 |
|---|---|
| author | Junfeng Wang Kai Yang Wanzhao Li Xinzhou Wang Jan Van den Bulcke Joris Van Acker |
| author_facet | Junfeng Wang Kai Yang Wanzhao Li Xinzhou Wang Jan Van den Bulcke Joris Van Acker |
| author_sort | Junfeng Wang |
| collection | DOAJ |
| description | Thermal modification can increase the physical stability and impact the mechanical strength of wood. It is necessary to understand the effects of modifications on the compressive stress of wood. In this study, Douglas fir (<i>Pseudotsuga menziessi</i>) blocks were modified at 180 °C (TM-180 °C) and 210 °C (TM-210 °C). The compressive stress of pure earlywood (EW), pure latewood (LW), and combined earlywood and latewood (ELW) specimens was measured. The specimens were compressed at 30% of their original thickness, and during the compression test the strain distribution of the ELW was recorded. In addition, the microstructures before and after compression were investigated, complemented with SEM to understand the structural changes taking place. The results showed that the compressive stress of the TM-180 °C specimens was the highest because the thermal modification increased the stiffness of cell walls and the homogenized strain distribution in the ELW specimens. The control specimens had a higher compression set recovery rate than the thermally modified specimens. The tracheid cell walls in the EW and LW specimens were flattened and buckled, respectively, due to compression. In the thermally modified materials, cell wall fissures and wood ray fractures in the EW and LW specimens, respectively, were observed. For the ELW specimens, the structural changes in the latewood were not obvious and the structural changes in the earlywood were less significant than in the full EW specimens. Compared to the EW specimens, the earlywood in the ELW specimens showed higher compression set recovery rates. It seems that structural failure in earlywood is limited when used in combination with latewood, resulting from the homogenized strain distribution in earlywood. |
| first_indexed | 2024-03-11T01:03:44Z |
| format | Article |
| id | doaj.art-7724da73308d4a99b2c3e6e64ce07b52 |
| institution | Directory Open Access Journal |
| issn | 1999-4907 |
| language | English |
| last_indexed | 2024-03-11T01:03:44Z |
| publishDate | 2023-07-01 |
| publisher | MDPI AG |
| record_format | Article |
| series | Forests |
| spelling | doaj.art-7724da73308d4a99b2c3e6e64ce07b522023-11-18T19:23:23ZengMDPI AGForests1999-49072023-07-01147137610.3390/f14071376The Impact of Earlywood and Latewood on the Compressive Stress of Thermally Modified Douglas FirJunfeng Wang0Kai Yang1Wanzhao Li2Xinzhou Wang3Jan Van den Bulcke4Joris Van Acker5Guangxi Key Laboratory of Superior Timber Trees Resource Cultivation, Nanning 530002, ChinaCollege of Materials Science and Engineering, Nanjing Forestry University, Longpan Road 159, Nanjing 210037, ChinaCollege of Materials Science and Engineering, Nanjing Forestry University, Longpan Road 159, Nanjing 210037, ChinaCollege of Materials Science and Engineering, Nanjing Forestry University, Longpan Road 159, Nanjing 210037, ChinaUGent-Woodlab, Laboratory of Wood Technology, Department of Environment, Faculty of Bioscience Engineering, Ghent University, Coupure Links 653, 9000 Ghent, BelgiumCollege of Materials Science and Engineering, Nanjing Forestry University, Longpan Road 159, Nanjing 210037, ChinaThermal modification can increase the physical stability and impact the mechanical strength of wood. It is necessary to understand the effects of modifications on the compressive stress of wood. In this study, Douglas fir (<i>Pseudotsuga menziessi</i>) blocks were modified at 180 °C (TM-180 °C) and 210 °C (TM-210 °C). The compressive stress of pure earlywood (EW), pure latewood (LW), and combined earlywood and latewood (ELW) specimens was measured. The specimens were compressed at 30% of their original thickness, and during the compression test the strain distribution of the ELW was recorded. In addition, the microstructures before and after compression were investigated, complemented with SEM to understand the structural changes taking place. The results showed that the compressive stress of the TM-180 °C specimens was the highest because the thermal modification increased the stiffness of cell walls and the homogenized strain distribution in the ELW specimens. The control specimens had a higher compression set recovery rate than the thermally modified specimens. The tracheid cell walls in the EW and LW specimens were flattened and buckled, respectively, due to compression. In the thermally modified materials, cell wall fissures and wood ray fractures in the EW and LW specimens, respectively, were observed. For the ELW specimens, the structural changes in the latewood were not obvious and the structural changes in the earlywood were less significant than in the full EW specimens. Compared to the EW specimens, the earlywood in the ELW specimens showed higher compression set recovery rates. It seems that structural failure in earlywood is limited when used in combination with latewood, resulting from the homogenized strain distribution in earlywood.https://www.mdpi.com/1999-4907/14/7/1376compressive stressearlywoodlatewoodthermal modificationstrain distribution |
| spellingShingle | Junfeng Wang Kai Yang Wanzhao Li Xinzhou Wang Jan Van den Bulcke Joris Van Acker The Impact of Earlywood and Latewood on the Compressive Stress of Thermally Modified Douglas Fir Forests compressive stress earlywood latewood thermal modification strain distribution |
| title | The Impact of Earlywood and Latewood on the Compressive Stress of Thermally Modified Douglas Fir |
| title_full | The Impact of Earlywood and Latewood on the Compressive Stress of Thermally Modified Douglas Fir |
| title_fullStr | The Impact of Earlywood and Latewood on the Compressive Stress of Thermally Modified Douglas Fir |
| title_full_unstemmed | The Impact of Earlywood and Latewood on the Compressive Stress of Thermally Modified Douglas Fir |
| title_short | The Impact of Earlywood and Latewood on the Compressive Stress of Thermally Modified Douglas Fir |
| title_sort | impact of earlywood and latewood on the compressive stress of thermally modified douglas fir |
| topic | compressive stress earlywood latewood thermal modification strain distribution |
| url | https://www.mdpi.com/1999-4907/14/7/1376 |
| work_keys_str_mv | AT junfengwang theimpactofearlywoodandlatewoodonthecompressivestressofthermallymodifieddouglasfir AT kaiyang theimpactofearlywoodandlatewoodonthecompressivestressofthermallymodifieddouglasfir AT wanzhaoli theimpactofearlywoodandlatewoodonthecompressivestressofthermallymodifieddouglasfir AT xinzhouwang theimpactofearlywoodandlatewoodonthecompressivestressofthermallymodifieddouglasfir AT janvandenbulcke theimpactofearlywoodandlatewoodonthecompressivestressofthermallymodifieddouglasfir AT jorisvanacker theimpactofearlywoodandlatewoodonthecompressivestressofthermallymodifieddouglasfir AT junfengwang impactofearlywoodandlatewoodonthecompressivestressofthermallymodifieddouglasfir AT kaiyang impactofearlywoodandlatewoodonthecompressivestressofthermallymodifieddouglasfir AT wanzhaoli impactofearlywoodandlatewoodonthecompressivestressofthermallymodifieddouglasfir AT xinzhouwang impactofearlywoodandlatewoodonthecompressivestressofthermallymodifieddouglasfir AT janvandenbulcke impactofearlywoodandlatewoodonthecompressivestressofthermallymodifieddouglasfir AT jorisvanacker impactofearlywoodandlatewoodonthecompressivestressofthermallymodifieddouglasfir |