考虑固化残余应力影响的Z-pin增韧复材压缩性能预测方法

Numerical study on curing residual stresses in compression of Z-pinned composites

Z-pin增韧技术可有效提高复合材料层间性能,但pin针的植入会引起材料纤维发生变向,造成富树脂区,降低面内性能。本文提出了一种考虑固化残余应力影响的Z-pin增韧复合材料面内压缩性能的预测方法。通过分析Z-pin增韧结构的细观形貌,建立了代表性单胞模型;充分考虑各组分材料的固化时变特性,建立了Z-pin增韧结构下的热-力-化学多场耦合模型;将前期计算得到的固化残余应力场作为预定义场带入面内压缩性能计算,得到的仿真结果与实验吻合度高。研究发现,固化过程中Z-pin周围会聚集大量残余应力,因而在压缩载荷下,Z-pin周围的材料性能较弱会最先产生裂纹缺陷,并逐渐向富树脂区扩展;纤维变向、富树脂区和固化残余应力的存在会显著降低增韧后复合材料的面内压缩性能。

The Z-pinning technology can effectively improve the interlaminar properties of composite materials,yet the implantation of Z-pins causes fiber distortion,resin-rich zones,and reduced in-plane properties.This paper proposes a numerical method to predict the in-plane compressive properties of Z-pinned composites,with curing effects into consideration.A representative unit cell model is established by analyzing the fine morphology of the Z-pinned structure.Considering the time-dependent properties of the cure process,we develop a coupled thermo-chemo-mechanical multi-field model for Z-pinned structures.The residual stress field obtained from the previous calculation is introduced as a predefined field in the calculation of in-plane compressive performance,and the simulated results are in good agreement with the experimental results.It is found that a large amount of residual stress accumulates around the Z-pin during the cure.Therefore,under compressive loads,weaker material properties around the Z-pin will first develop crack defects,gradually extending to the resin-rich regions.The presence of fiber orientation,resin-rich regions,and cure-induced residual stresses significantly reduce the in-plane compressive performance of Z-pinned composites.