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Scientia Silvae Sinicae ›› 2015, Vol. 51 ›› Issue (2): 121-128.doi: 10.11707/j.1001-7488.20150215

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Development of Micromechanical Technique and Application on Wood Science

Lin Lanying, Qin Lizhe, Fu Feng   

  1. Key Laboratory of Wood Science and Technology of State Forestry Administration Research Institute of Wood Industry, CAF Beijing 100091
  • Received:2014-03-10 Revised:2014-07-04 Online:2015-02-25 Published:2015-03-11

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Abstract:

As an important method to measure the micro and nano mechanical properties of materials, micromechanical characterization technique has been already extensively used to study the ultrastructure and mechanical behavior of materials. With the development of characterization technique, research scale shrank tremendously from nano to ultra-nano scale, from molecular to super-molecular scale, even to particle scale. Micromechanical characterization technique can be classified into two types according to the specimen information: nano mechanical testing technique (probe technique) and ultra-nano mechanical testing technique (microscopy techniques). The nano mechanical testing technique included quasi-static nanoindentation, dynamic nanoindentation and dynamic modulus imaging. The ultra-nano mechanical testing technique included atomic force microscopy (AFM) and new techniques based on AFM. Wood is a porous and layered heterogeneous anisotropic natural polymer. It is composed of layers with varying thickness. Cell wall is a central factor determining the properties of wood and wood fiber materials. It is also the essential stressed structure of wood. The mechanical properties of wood cell are depended on the wall layer structure, distribution and combination of chemical compositions. Researching the nano mechanical properties, distribution and affection of cell walls is critical for effective designing of wood and modified wood. Since nanoindentation was first successfully applied in wood cells of nature wood by Wimmer and his colleagues, scholars at home and abroad had generally adopted quasi-static nanoindentation and dynamic nanoindentation to study the nano mechanical properties of cell walls, such as hardness, modulus, creep properties, viscoelasticity, etc. As an interfacial layer or an interfacial phase with nano-scale thickness, the interfaces of wood materials impact their strength, stiffness and fracture toughness. Interfacial mechanics are the key of the whole mechanical properties of wood-based composites. They are also major causes of deformation and strength descent. The researches of the attributes and characteristics of interface are of great value of property evaluating and design optimizing of wood-based composites. The main researches in wood science field included bonding interface, interface of fiber reinforced polymers and micromechanics of coating over the woodworks. Micromechanical characterization technique was tending to high resolution and quantitative evaluation with researching scale shrinking, and already can be performed mechanical information imaging with nano resolution. Development of micromechanical characterization technique can provide great convenience for wood science research. However, tremendous room is needed for improvement. In the future, we should focus on the following three topics: Firstly, to conduct micromechanical technique standardization research, specify testing process and to ensure testing results consistency and reliability. Secondly, to establish relatively complete mechanical system from macrocosm to microcosm, and to further dissect mechanical behavior and failure mechanisms. Thirdly, to build the micro coupling techniques between mechanical, chemical, physical and environmental, so as to enrich the study of wood and wood-based composites at nano scale.

Key words: micromechanical, wood, wood-based composites, cell wall, interface

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