纤维自动铺放工艺制备单向罐外固化复合材料的拉-拉疲劳性能

纤维自动铺放工艺（AFP）制备罐外固化（OOA）复合材料中难以避免出现铺放缺陷如缝隙（Gaps），影响复合材料的力学和疲劳性能。选取罐外固化预浸料IM7/CYCOM5320-1，采用自动铺放工艺制备正常（NDS）和预置缺陷（DS）复合材料，探讨了铺放缺陷对0°单向罐外固化复合材料拉-拉疲劳性能的影响，建立了疲劳寿命和剩余强度衰减模型。结果表明，相比于NDS罐外固化复合材料，DS的静态拉伸强度降低5.90%，拉伸模量降低6.54%；NDS和DS复合材料的疲劳寿命均随疲劳载荷的增大而减少，DS的疲劳寿命一直低于NDS；随着疲劳载荷的增加，二者的疲劳寿命相差越大，铺放缺陷的影响也越来越明显；NDS和DS复合材料在拉-拉疲劳测试前期的力学强度均维持平稳状态，达到一定疲劳周数后力学强度明显下降；应力水平越高，铺放缺陷对罐外固化复合材料的剩余强度影响越明显，而不同应力比下，缺陷对剩余强度的影响一致。

Tension-tension fatigue performance of unidirectional out-of-autoclave composite manufactured by automated fiber placement

In manufacturing of Out-of-Autoclave (OOA) composites based on Automated Fiber Placement (AFP), it is inevitable to have defects such as gaps, which will affect the mechanical and fatigue properties of the final parts. In this work, out-of-autoclave prepregs IM7/CYCOM5320-1 are selected, Non Defective Samples (NDS) and Defective Samples (DS) are manufactured by automated fiber placement process. The influence of defects on the tension-tension fatigue behavior of 0° unidirectional out-of-autoclave composites is investigated. The fatigue life model and the residual strength degradation model are developed. The results reveal that due to laying defects, the static tensile strength of the composite decreased by 5.90%, and the tensile modulus decreased by 6.54%. As the fatigue load increases, the fatigue life of both non defective and defective composites shows a downward trend, while the fatigue life of the defective composite is always less than that of the non defective one. The longer the fatigue life is, the more differences are there between non defective and defective composites. Meanwhile, the influence of defects also increases with the fatigue life. In the investigation of the residual strength, both non defective and defective composites exhibit a constant behavior at the beginning of tension-tension fatigue tests, followed by a dramatical drop at specific fatigue cycles. Considering the influence of defects on residual strength of composites, the higher the stress level is, the more obvious the effect becomes. However, defects exhibit a similar influence on residual strength when the stress ratio is different.