Monitoring of Beech Glued Laminated Timber and Delamination Resistance of Beech Finger-Joints in Varying Ambient Climates
Abstract
:1. Introduction
2. Materials and Methods
2.1. Specimens and Adhesives
- One-component polyurethane (PUR).
- Two-component melamine-urea-formaldehyde (MUF)
- Two-component phenol-resorcinol-formaldehyde (PRF).
2.2. Monitoring Experiment of Beech Glued Laminated Timber in Varying Ambient Climates
- Day 1: Pouring the anhydrite screed
- Day 3: First ventilation after 48 h, afterwards 1–3 × daily ventilation (each 10–15 min, weekdays)
- Day 7: Start the heating program 7 days after pouring the anhydrite screed
- Day 7–10: Heat-up phase up to 25 °C
- Day 11–18: Increase the room temperature by 5 °C/day until 45 °C was reached
- Day 19–32: Maintain a constant room temperature of 45 °C (±5 °C) for 14 days
2.3. Manufacture of Finger-Jointed Delamination Specimens and Testing under Varying Ambient Climates
3. Results and Discussion
3.1. Monitoring of Climatic Conditions and Changes in Wood Moisture Content
3.2. Delamination Resistance of Beech Finger-Joints in Varying Ambient Climates
3.3. Effect of the Test Procedures on the Change in Thickness of the Delamination Specimens
4. Conclusions and Outlook
- In beech glulam, the monitoring experiment showed a clear MC gradient between the inner and near-surface wood. In particular, the outer layers of the glulam and the finger-joints located there are directly exposed to the moisture changes. In the outer layers, the beech wood reacted quickly to moisture changes in the ambient conditions;
- In the course of the three-week alternating climate regime, there are sometimes major delaminations of the finger-joint bonding. The adhesive systems used showed approximately the same delamination resistance after the alternating climate regime;
- PRF-bonded beech finger-joints fulfilled the requirements of EN 301 (2018) [4]. A high proportion of the specimens bonded with PUR were also able to pass the standard requirements at high MCbond.
- The load on wood adhesives in a practical construction application (at least initially) is different from that in a standardised performance test for the classification of adhesive systems (delamination test according to EN 301 (2018) [4]);
- The results show that delamination resistance remains a critical key property for the realisation of glulam made of beech wood;
- More elastic adhesive systems can have an advantage over more brittle systems in the case of moisture-related dimensional changes;
- The bonding performance of the adhesive systems is dependent on the bonding parameters, as determined here for PUR and MCbond;
- The influence of a long-term alternating climate regime on the properties of finger-joint bonding is to be investigated;
- It is to be examined whether the annual ring orientation of the delamination specimens has an influence on the delamination of the bonding.
Author Contributions
Funding
Acknowledgments
Conflicts of Interest
References
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Adhesive | MCbond (%) | c | a | b | c | a | b |
---|---|---|---|---|---|---|---|
Mean Delamtot [%] | Mean Delammax [%] | ||||||
MUF | 8 | 2.0 (±1.5) | 28.3 (±6.2) | 33.0 (±8.3) | 14.4 (±10.4) | 47.4 (±3.7) | 48.3 (±4.7) |
12 | 1.9 (±2.0) | 37.8 (±9.1) | 33.7 (±4.8) | 14.6 (±9.4) | 49.3 (±2.3) | 47.8 (±5.4) | |
15 | 0.7 (±0.7) | 29.6 (±7.3) | 30.7 (±4.6) | 11.0 (±2.9) | 44.9 (±7.2) | 49.8 (±0.6) | |
PUR | 8 | 3.0 (±2.1) | 17.0 (±4.9) | 19.5 (±7.3) | 16.9 (±11.9) | 46.0 (±7.9) | 40.6 (±10.2) |
12 | 1.6 (±1.6) | 17.3 (±9.2) | 17.6 (±5.3) | 18.1 (±16.8) | 39.9 (±12.1) | 42.6 (±7.9) | |
15 | 0.2 (±0.3) | 8.6 (±3.9) | 13.1 (±8.4) | 4.8 (±10.3) | 26.3 (±9.9) | 38.3 (±12.9) | |
PRF | 8 | 0.4 (±0.6) | 2.6 (±1.9) | 3.4 (±1.0) | 11.7 (±17.6) | 8.8 (±3.9) | 18.7 (±16.1) |
12 | 0.6 (±0.7) | 6.7 (±3.7) | 3.3 (±1.0) | 13.1 (±16.6) | 25.7 (±13.6) | 20.7 (±15.1) | |
15 | 1.0 (±1.0) | 4.7 (±2.3) | 4.7 (±2.2) | 18.6 (±20.3) | 23.9 (±12.4) | 25.6 (±17.6) |
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Stolze, H.; Schuh, M.; Kegel, S.; Fürkötter-Ziegenbein, C.; Brischke, C.; Militz, H. Monitoring of Beech Glued Laminated Timber and Delamination Resistance of Beech Finger-Joints in Varying Ambient Climates. Forests 2021, 12, 1672. https://doi.org/10.3390/f12121672
Stolze H, Schuh M, Kegel S, Fürkötter-Ziegenbein C, Brischke C, Militz H. Monitoring of Beech Glued Laminated Timber and Delamination Resistance of Beech Finger-Joints in Varying Ambient Climates. Forests. 2021; 12(12):1672. https://doi.org/10.3390/f12121672
Chicago/Turabian StyleStolze, Hannes, Mathias Schuh, Sebastian Kegel, Connor Fürkötter-Ziegenbein, Christian Brischke, and Holger Militz. 2021. "Monitoring of Beech Glued Laminated Timber and Delamination Resistance of Beech Finger-Joints in Varying Ambient Climates" Forests 12, no. 12: 1672. https://doi.org/10.3390/f12121672