孔隙率对碳纤维/尼龙6复合材料湿热性能影响的数值模拟研究

Numerical study on the effect of void content on hygrothermal performances of carbon fiber reinforced polyamide 6 composites

孔隙在复合材料制造过程中广泛存在,在湿热环境下孔隙的存在会改变应力场和水分场,进而影响复合材料的吸湿性能与力学老化性能。对碳纤维/尼龙6(Carbon fiber reinforced polyamide 6,CF/PA6)复合材料在不同温度浸水环境下吸湿老化后的力学性能测试,研究了温度与吸湿量对其力学性能的影响及强度与模量等力学参数的演化规律,建立吸湿参数与力学参数的关联函数。基于随机顺序吸附法算法(Random sequential adsorption,RSA),建立了纤维、界面和孔隙随机分布的代表性体积单元(Representative volume element,RVE)模型。在本构模型中引入依赖于吸湿量的退化因子,研究了孔隙含量对复合材料横向拉伸、压缩、剪切强度和模量的影响,揭示了湿热老化前后不同的失效机制。结果表明:在热湿老化前,由于应力集中,孔隙会导致复合材料力学性能下降,孔隙率含量每增加1%,横向拉伸强度降低6.4%;湿热老化后,基体吸湿塑化效应是复合材料力学性能降低主要因素,对应降低率为3.86%。

Voids are comment defects generated during the manufacturing process and highly sensitive to moisture in the hygrothermal environment.The presence of voids will change the stress field and moisture field,which has deleterious effects on the mechanical performances.The mechanical properties of carbon fiber reinforced polyamide 6(CF/PA6)composites after hygrothermal aging under different temperature immersion environment were tested to study the effects of temperature and water absorbed content on the mechanical properties.The correlation function between water content and mechanical parameters was established.Based on the random sequential adsorption algorithm(RSA),the representative volume element(RVE)model with random distribution of fibers,interfaces and voids was established.The quantitative effects of voids content on strength and modulus under the loading of transverse tension,compression and shear were investigated,by introducing a degradation factor dependent on water content into the constitutive model,and the failure mechanisms before and after hygrothermal aging were revealed.Conclusively,before hygrothermal aging,voids induce the decrease of mechanical properties due to stress concentration,and every 1%increase in the voids content results in a 6.4%decrease of transverse tensile strength.However,matrix degradation due to the absorbed water content after hygrothermal aging is the dominant factor,and the corresponding rate is 3.86%.