Reinforced Mechanism in Polymer Composites by X-ray Diffraction

用X射线衍射法研究了聚合物复合材料中的应力传递、应力集中以及由此产生的增强效应的机理。研究了纤维与基体界面脱粘的断裂机理，以及粘结对增强效果的影响。首先，在与纤维方向垂直的方向上对高性能聚乙烯纤维单向增强环氧复合材料施加应力。外加应力传递到掺入的光纤中，这很容易被检测到赤道X射线衍射峰的衍射峰的移动。传递到纤维上的应力可以通过将结晶应变乘以聚乙烯结晶区的弹性模数来估计。利用这种“X射线衍射法”，可以原位、无损地测定聚合物基复合材料中掺入纤维的应力，即增强效果。纤维经铬酸处理后，应力向纤维传递较好，说明纤维与基体之间的粘结对纤维垂直方向的增强起着重要作用。此外，还发现纤维的表面处理改变了断裂模式。力学性能是用混合物在纤维轴方向上的作用来表示的，并用X射线衍射仪对其进行了表征。对碳纤维增强复合材料和聚对苯撑苯并双恶唑增强复合材料也进行了同样的实验。这项技术还将被应用于研究水分、时间、温度的影响。

X-ray Diffraction method was utilized to investigate the mechanism of stress transfer, stress concentration, and resulting reinforcement effect in polymer composite. Fracture mechanism based on the debonding at the interface between fiber and matrix, the effect of adhesion on the reinforcement have been also investigated. First, the stress was applied to the high-performance polyethylene fiber uni- directionally reinforced epoxy composite in the direction perpendicular to the fiber direction. The applied stress was found to be transmitted to the incorporated fiber, which could be easily detected as the diffraction peak shift of the equatorial x-ray diffraction peak. The stress transmitted to the fiber can be estimated by multiplying the crystal strain by the elastic modulus of the crystalline regions of polyethylene. By using this "X-ray Diffraction Technique" , the stress on tghe incorporated fiber, that is, the reinforced effect in polymer composite can be determined in situ and non-destructively. When the fiber was treated with chromic acid, the applied stress became well trasmitted to the fiber, which indicated that the adhesion between the fiber and matrix plays an important role for the reinforcement in the perpendicular direction. Further, the fracture mode was found to be changed by the surface treatment of the fiber. The mechanical property was found to be expressed by using the role of mixture in the direction of fiber axis, which was also clarified by utilizing the x-ray diffraction. Same kinds of experiments were also performed for carbon fiber reinforced composite, and poly (p-phenylene benzobisoxazole) reinforced composites. This technique will be also applied to investigate the effect of moisture, time, temperature.