四川轻化工大学学报：自然科学版

以碳纤维增强聚醚醚酮（PEEK）复合材料为代表的热塑性复合材料近年来被广泛应用于航空航天的热端结构上，相关构件在服役过程中通常会受到循环载荷，为保证构件的使用安全，有必要对材料的循环变形行为进行研究。通过对0°、45°、90°不同纤维方向的碳纤维增强PEEK复合材料T700/PEEK进行单调拉伸、应力控制循环和应变控制循环实验，系统地研究了该复合材料的平均应力松弛和棘轮行为等循环变形特性。研究表明：3种不同纤维角度试样的单调拉伸应力-应变响应有较大区别，0°方向的弹性模量约为90°方向的11倍。在非对称应变加载条件下，复合材料出现平均应力松弛现象，在前20圈平均应力下降速度很快，至100圈后开始趋于稳定；纤维方向和给定的应变幅值以及平均应变的大小是影响平均应力松弛现象的重要因素。在非对称应力加载条件下，复合材料表现出棘轮行为，且该行为是各向异性的。对于拉伸-卸载时的峰值应力，非对称拉压时的应力幅值、平均应力以及应力比都对复合材料的棘轮行为有较大影响。该复合材料的棘轮行为还表现出明显的率相关性。

Thermoplastic composites, such as carbon fiber-reinforced polyether-ethe-ketone(PEEK) matrix composites, have been widely used in aerospace hot-end structures in recent years, and the related components are usually subjected to cyclic loading during service, so it is necessary to carry out experimental studies on the cyclic deformation behavior of the materials in order to ensure the safety of the components in use. The average stress relaxation and ratcheting behavior of carbon fiber-reinforced PEEK matrix composites(T700/PEEK) with different fiber orientations at 0°, 45°, and 90° are systematically studied by monotonic tensile, stress-controlled cycling and strain-controlled cycling experiments. It is shown that the monotonic tensile stress-strain curves of three components with different fiber angle has large difference, and the elastic modulus of the fiber with an orientation at 0° is about 11 times that of the fiber with an orientation at 90°. Under asymmetric strain loading conditions, the composites behave average stress relaxation phenomenon, and the average stress decreased rapidly during the first 20 cycles until it began to stabilize after 100 cycles. The fiber orientation and the given strain amplitude as well as the magnitude of the average strain are important factors affecting the average stress relaxation phenomenon. Under asymmetric stress loading conditions, the composites show ratcheting behavior,which is anisotropic. The peak stress during tension-unloading, stress amplitude, average stress, and stress ratio during asymmetric tension-compression all have greater influences on ratcheting behavior of the composites,which also shows obvious rate dependence.