Liu Wenqiang, Shomali Ali, Zhang Chi, Coasne Benoit, Carmeliet Jan, Derome Dominique
Department of Civil and Building Engineering, Université de Sherbrooke, Sherbrooke, Canada.
Department of Mechanical and Process Engineering, ETH, Zurich, 8093, Zurich, Switzerland.
Carbohydr Polym. 2024 Nov 1;343:122429. doi: 10.1016/j.carbpol.2024.122429. Epub 2024 Jun 24.
Our starting hypothesis is that Polyethylene glycol (PEG) can be utilized to mix with the biopolymers for consolidating fiber-reinforced composites without deteriorating their hygro-mechanical properties. The effect of PEG on the shear strength during pull-out of crystalline cellulose (CC) fiber out of an amorphous cellulose matrix is simulated with molecular dynamics. The interfacial shear stress shows a stick-slip behavior and is weakened with increasing moisture content. Shear strength increases at low moisture content, manifesting a slight strengthening of interfacial mechanical property due to cohesive forces exerted by the water molecules. At higher moisture content, shear strength is reduced due to breakage of the hydrogen bonds between CC and matrix by water molecules. When adding PEG, amorphous cellulose around the crystalline fiber is replaced by PEG, forming a mixture with amorphous cellulose. It is found that PEG-treated CC-AC composite maintains its shear strength and the presence of PEG does not deteriorate the dependence of the shear strength on moisture content. A shear strength model based on the number of hydrogen bonds between the fiber and the matrix is developed, which validates our initial hypothesis by unraveling the fundamental mechanisms at play. The model reveals that, although the shear strength per hydrogen bond between the fiber and PEG is lower than the shear strength per hydrogen bond between the fiber and amorphous cellulose, the final shear strength is partly compensated by an increase in the total number of hydrogen bonds with increasing PEG ratio. Since PEG reduces the moisture content in the composite at low relative humidity, PEG treated wood in museum conditions will show enhanced shear strength. The framework is a basis for further investigation of realistic archaeological wood with PEG-treatment.
我们最初的假设是，聚乙二醇（PEG）可用于与生物聚合物混合，以加固纤维增强复合材料，而不会使其湿力学性能恶化。利用分子动力学模拟了PEG对结晶纤维素（CC）纤维从无定形纤维素基质中拔出过程中剪切强度的影响。界面剪切应力呈现出粘滑行为，并随着含水量的增加而减弱。在低含水量时剪切强度增加，这表明由于水分子施加的内聚力，界面力学性能略有增强。在较高含水量时，由于水分子破坏了CC与基质之间的氢键，剪切强度降低。添加PEG时，结晶纤维周围的无定形纤维素被PEG取代，与无定形纤维素形成混合物。研究发现，经PEG处理的CC-AC复合材料保持了其剪切强度，且PEG的存在并未破坏剪切强度对含水量的依赖性。建立了一个基于纤维与基质之间氢键数量的剪切强度模型，该模型通过揭示其中的基本机制验证了我们最初的假设。该模型表明，尽管纤维与PEG之间每个氢键的剪切强度低于纤维与无定形纤维素之间每个氢键的剪切强度，但最终的剪切强度会随着PEG比例的增加通过氢键总数的增加而得到部分补偿。由于PEG在低相对湿度下降低了复合材料中的含水量，在博物馆环境中经PEG处理的木材将表现出增强的剪切强度。该框架是进一步研究经PEG处理的实际考古木材的基础。
