单向热固性预浸料面内剪切行为表征及黏弹性本构建模

In-plane shear behavior characterization of unidirectional thermoset prepreg and its viscoelastic constitutive modeling

单向热固性预浸料的面内剪切变形对最终复合材料构件的成型质量和力学性能有着显著影响。对此,本文研究了单向热固性预浸料在不同成型温度和加载速率下的面内剪切及应力松弛行为。结果表明:单向热固性预浸料呈现出与温度和加载速率强相关的非线性面内剪切变形行为,剪切变形对加载速率的敏感性随着温度的升高而降低,应力松弛速度随着温度的升高而加快,温度越高将会越快处于应力松弛稳定状态。基于单向热固性预浸料的面内剪切及应力松弛行为,构建了精准追踪纤维方向变化的广义Maxwell黏弹性本构模型,并编写VUMAT用户材料子程序,对单向热固性预浸料的偏轴拉伸阶梯加载应力松弛进行模拟,与试验结果表现出较好的一致性,证明了该本构模型的有效性和正确性。

The in-plane shear deformation behavior of unidirectional thermoset prepreg has significant effect on the forming quality and mechanical properties of composite parts after hot diaphragm forming.In this paper,the in-plane shear and stress relaxation behavior of unidirectional thermoset prepreg at different forming temperatures and loading rates were investigated.The test results show that the unidirectional thermoset prepreg exhibits a nonlinear in-plane shear deformation behavior strongly related to temperature and loading rate,and the sensitivity of shear deformation to loading rate decreases with the increasing of temperature.The relaxation rate of unidirectional thermoset prepreg accelerates with the increasing of temperature,and the sooner it is in a stable state.Based on the in-plane shear stress relaxation behavior of unidirectional thermoset prepreg,a generalized Maxwell viscoelastic constitutive model was constructed,which could accurately track fiber orientation change.The viscoelastic constitutive model was implemented in the user material subroutine VUMAT in Abaqus.The off-axis tensile stress relaxations were simulated.It is in good agreement with the experimental results,indicating the effectiveness of the viscoelastic constitutive model.