分数阶反常扩散下湿热弹性复合材料的断裂

Transient moisture-heat effects such as in the process of steam-cured concrete can strongly influence the mechanical properties of the materials. The classical heat conduction and mass transfer cannot describe the transient characteristics of hygrothermal diffusion. Based on the basic principles of thermodynamic, heat and mass transfer, and solid mechanics, under the condition of hygrothermal coupling, this project aims at applying fractional abnormal diffusion to describe the transient process of heat and moisture transfer and to establish time-fractional generalized hygrothermoelasticity. The mechanical behaviors of such composite materials containing defects are systemically analyzed through theoretical analysis, numerical simulation and experiment test when subjected to complicated loading conditions such as conduction and convection of moisture and heat as well as thermal radiation. The relevance of the hygrothermal effect, the latent heat of phase transformation, or hygrothermal relaxation times and the mechanical performance of composite materials is revealed. The influence of crack’s geometry and distribution on the propagation direction and path of crack growth is formulated. Failure mechanism of layered composite materials with hygrothermoelastic coupling is shed light on due to the difference of coupled heat and moisture transfer process in dissimilar materials via the hygrothermoelastic models of different time-fractional orders. It provides a theoretical support for engineering applications of the fields related to deformation and fracture of composite materials arising from transient hygrothermoelastic coupling.

混凝土蒸养过程中瞬态湿热效应强烈影响材料的力学性能。通常的导热传湿不能描述湿热扩散的瞬态特性。基于热动力学、传热传质学、固体力学的基本原理，本项目旨在导热传湿耦合条件下，通过分数阶反常扩散描述材料内部的导热传湿瞬态过程，建立分数阶广义湿热弹耦合理论。通过理论分析、数值仿真和试验测试，系统分析受湿热传导、对流和热辐射等复杂条件下此类含缺陷复合材料的力学行为，揭示湿热效应、相变潜能、湿热弛豫时间对复合材料力学性能之间的关联，阐明湿热耦合条件下裂纹几何尺寸及分布对裂纹扩展方向和路径的影响规律，通过不同阶数的分数阶模型分析不同材料内部耦合传热传湿过程的差异，揭示层状复合材料的湿热弹性耦合断裂失效机理。为瞬态湿热耦合诱导的材料变形和断裂的工程应用提供理论支撑。

应用工程领域（如蒸养混凝土和固体火箭点火等过程中）经常发生超高温湿热耦合效应，并进一步强烈影响材料的力学性能。由于高温度梯度及超快速的热流，通常的Fourier热传导和Fick扩散定律并不能不能描述湿热耦合扩散的瞬态特性。该项目基于热力学、传热传质学、固体力学的基本原理，引入分数阶反常扩散描述材料内部的导热传湿瞬态过程，建立了分数阶广义湿热弹耦合理论，研究了考虑分数阶的湿热弹性材料中的裂纹问题，分析了无限介质、有效厚度及功能梯度材料中的直裂纹、币形裂纹受到湿热冲击等荷载工况下湿热应力的分布规律；系统分析了受湿热传导、对流和热辐射等复杂条件下此类含缺陷复合材料的力学行为，揭示湿热效应、湿热弛豫时间对复合材料力学性能之间的关联；提出了微纳米梁板湿热结构的湿热弹性阻尼模型，揭示了分数阶、微纳米尺寸及湿热特性对结构的品质因子影响，为瞬态湿热耦合诱导的材料变形和断裂的工程应用提供理论支撑。依托该项目，共发表SCI论文19篇，包括Int J Solids Struct、Appl Math Model、Theo Appl Fract Mech、Int J Heat Mass Transfer、Int Comm Heat Mass Transfer、Int J Thermal Sci 等期刊。