资料科学概论谜底(国外英文资料).docVIP

材料科学概论答案(国外英文资料) The characteristics of the high polymer material Composition: is mainly composed of C, H, O (inorganic polymer, such as glass) molecular weight polydispersity, only a certain range, is a mixture of molecular weight of homologue. The molecular weight is large (104-107, or more). There is no fixed melting point, only a wide range of temperature; ? There is no boiling point and fixed melting point, and the intermolecular forces are large enough to heat up to 200oC - 300oC and material damage (degradation or crosslinking). ? Chain structure? Flexible chain ? ? ? ? Because of this outstanding feature, the polymer shows unique performance, which is characterized by three high and one low disappearing. Both: N high molecular weight n high viscosity, n crystallinity low, n no gas. ?? Therefore, these characteristics also give high polymer materials (such as composite materials, rubber etc.) high strength, high toughness, high elasticity and so on. The main chains of most polymers have certain internal rotational degrees of freedom. The definition and meaning of elastic modulus Definition: generally speaking, to impose an external effect of elastomer, elastic experience change in shape (called strain), the modulus of elasticity is generally defined: stress divided by the strain. Meaning: Elastic modulus is an important performance parameters of engineering materials, from a macro perspective, the modulus of elasticity is a measure objects resistance capability of the elastic deformation, from the micro perspective, is the bonding strength between atoms and ions or molecules. All factors affecting the strength of the bond can influence the elastic modulus of the material, such as bonding mode, crystal structure, chemical composition, microstructure, temperature and so on. Depending on the composition of the alloy, different heat treatment condition, different cold plastic deformation, the value of the metal material will be 5% or more. But as a whole, the el