计及热效应和湿分扩散的耦合黏弹性本构方程

高聚物在电子和航空等领域得到广泛运用,由于高聚物的亲水性,常常发生由于湿热引起的结构失效甚至材料的断裂.近年来,有实验显示,高聚物中的湿热效应及其力学反响是相互影响的,同时,考虑到高聚物的黏弹性,发展新的包含湿热效应的黏弹性本构方程来描述该问题是必要的.本文基于不可逆热力学的基本原理,运用连续介质力学的方法,通过引入内变量表示高聚物的黏性效应,基于 Helmholtz自由能导出一种热、湿分和黏弹性力学性质三场耦合的本构关系和系统控制方程,对实际的分析应用有较强的指导意义.

COUPLED VISCOELASTIC CONSTITUTIVE RELATIONS INVOLVING THERMAL EFFECT AND MOISTURE DIFFUSION PROCESS

In recent years, the failure caused by moisture and heat was often observed in hy-drophilic polymer structures, such as plastic packages and adhesive joints etc. It was found that moisture diffusion, heat conduction and mechanical response in polymers are coupled and affected each other. It is necessary to develop a set of full coupling constitutive relations to model the viscoelasticity and hydrophilicity of polymers. In this paper, the constitutive equations of the coupling problem, which involve effects of heat and moisture, have been developed on the basis of continuum thermodynamics in virtue of Helmholtz free energy. In this development, a group of internal variables is introduced to characterize the viscous behaviors of polymers. The work presents a fundamental framework to analyze the coupling problems due to heat and moisture transmit into viscoelastic materials.