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本研究用真空热压法制备了两种不同纤维体积分数的单向硼纤维增强铝(B/Al)复合材料,进行了动态拉伸试验。通过在备有拉伸台的扫描电镜(SEM)下缓慢加载,连续观察了各种偏轴角纤维外露试样的断裂过程。并测定了纤维外露试样及完整试样的强度及其载荷-位移曲线。结果表明:复合材料纵向,即纤维方向与拉伸轴的夹角(偏轴角)对断裂机制有极大影响,试样的破坏符合一定规律;复合材料强度与偏轴角的关系同最大应变能理论所揭示的规律相一致。由此提出了B/Al复合材料在小角拉伸时的正断模型和在大角拉伸时的剪断模型,阐明了B/Al复合材料裂纹萌生,扩展及连接的微观断裂过程。研究还表明,两种模型过渡的特征转折角与最优偏轴角之间可能存在某种相对应的关系。
In this study, two kinds of unidirectional boron fiber reinforced aluminum (B / Al) composites with different fiber volume fractions were prepared by vacuum hot pressing. The dynamic tensile tests were carried out. The fracture process of various off-axis fiber exposed samples was continuously observed by slowly loading under a scanning electron microscope (SEM) equipped with a tension stage. The strength and load-displacement curve of the fiber exposed sample and the intact sample were measured. The results show that the longitudinal direction of the composite, that is, the angle between the fiber direction and the stretching axis (off-axis angle) has a great influence on the fracture mechanism. The failure of the sample conforms to certain rules. The relationship between the strength of the composite and the off- The rules revealed by theory are consistent. Based on this, the normal breaking model of B / Al composites at small angle and the shear model at high angle are proposed. The microscopic fracture process of B / Al composites is described in terms of initiation, propagation and connection. The research also shows that there may be some corresponding relationship between the characteristic turning angle and the optimal off-axis angle of the two models.