| Summary: | 碩士 === 國立臺灣大學 === 森林環境暨資源學研究所 === 99 === With the progress of technology, the trend of material science has shifted from macro-scale to micro-scale study. Atomic force microscopy (AFM), which probes via the Van der Waals force between atoms, can be applied in nanoindentation technology and have detailed analysis of the mechanical properties and the structure of materials. With the understanding of the surface properties and nanoindentation mechanics, we can make the best use of materials in academic research and industrial applications. It has large potential in both two fields.
The S2 cell wall layer of common softwood species in Taiwan are studied through nanoindentation in our study. The micro-mechanics and biological properties such as lignin content and microfibril angles (MFA) are studied. The results indicate that there are high variability of the mechanical properties between early and latewood in micro-scale. It is affected by the differences of wood components and structures. Some plastic deformations may also exist due to the effect of indentation loading parameters.
The trend of elastic modulus is close to the model calculation and the consideration of the geometry of indentation probes. It decreases with the increase of MFA, but shows a more gentle curve than macro study due to micro-scale observations. Furthermore, the hardness in micro scale is generally decrease with the increasing MFA, but some deviating samples exist. Considering the material properties of wood, we can infer that the micro hardness is affected by matrix, structure, and the inhomogenerous nature of wood.
From the results of our study, the mechanical properties of wood in micro scale are much more complex than macro ones. And there is also high variability exist. The study on the mechanical properties of wood in micro scale still has large potential in the future. Our study provides a preliminary research on the material preparation and mechanical properties for the nanoindentation of Taiwanese tree species, which serves as references of further researches in the future.
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