平纹编织碳纤维增韧碳化硅复合材料的力学性能及损伤演化

MECHANICAL PROPERTY AND DAMAGE BEHAVIOR OF SILICON CARBIDE COMPOSITES TOUGHENED BY CARBON FIBERS PLAIN-WOVEN

通过平纹编织碳纤维增韧碳化硅复合材料的拉伸、压缩和剪切的单向与循环加–卸载实验,分别研究了材料在拉伸载荷、压缩载荷和剪切载荷作用下的力学性能和损伤演化过程。结果表明:在压缩载荷作用下,材料的压缩性能下降很小,基体开裂,纤维界面脱粘和纤维束断裂为主要的失效机理;材料在拉伸和剪切载荷作用下,损伤演化过程有所区别。材料拉伸损伤演化经历损伤初始阶段、损伤加速阶段和损伤减缓阶段,为韧性断裂,损伤破坏主要表现为:基体开裂、横向纤维束开裂,界面层脱粘、层间剥离和纤维断裂;在剪切载荷作用下,经历损伤加速阶段和损伤减缓阶段,基体开裂、界面层脱粘和纤维断裂为主要的损伤机理,试样最后在最窄截面位置形成平断面。基于实验研究结果,采用回归分析方法,分别给出了材料在拉伸载荷和剪切载荷作用下损伤演化方程式。

In order to investigate the mechanical behavior and damage evolution process of plain woven silicon carbide composites reinforced by carbon fibers, an experimental study of composites under tensile loading, compress loading and shear loading, respectively was performed. Damage evolution models were presented to disclosure damage evolution law. The influence of compress stress on modulus is inconspicuous. The matrix cracking, interfacial debonding, and fiber bundle fracture are the major compress damage mechanisms. The tensile tests show that damage begins at a stress level of about 45 MPa, and the damage process contains three stages： the first is initial damage stage in which the initial micro-cracks of composite develop; the second is accelerating stage that the new micro-cracks appear and open; the last is decelerating stage that the micro-cracks deflect. The tensile damage behavior includes： matrix micro-cracking, transverse bundle cracking, debonding of fiber/matrix interface, ply delamination and fiber fracture. The damage evolution process under shear loading is different from under tensile loading. The damage process under shear loading only contains accelerating stage and decelerating stage. The matrix cracking, debonding of fiber/matrix interface, and fiber fracture are major shear damage mechanisms. Based on experimental results and statistical analysis, the equations about damage evolution under tensile loading and shear loading were provided.