Microstructure-Based Multi-Physics Characterisation and Modelling of Magnetorheological Elastomers

磁流变弹性体(MRE)是一种多相、多功能的复合材料，其磁性颗粒悬浮在非磁性弹性体固体中。通过改变外加磁场，磁流变液的机械性能几乎可以在瞬间可逆地改变和控制。因此，磁流变液被认为是一类智能材料，在许多工业应用(例如，自适应调谐减振器、刚度可调支架和人造肌肉)中具有广阔的应用前景。然而，由于磁流变液的非线性和各向异性行为(包括颗粒的非线性铁电特性、基质的非线性机械响应以及由材料微观结构和外部磁场引起的各向异性)难以精确建模，目前缺乏磁流变液的通用本构模型，这使得目前很难在虚拟环境中模拟和优化磁流变液应用的设计。鉴于计算机辅助工程在当今设计方法中的重要性，这显然是阻碍MRE广泛开发的一个重大障碍。此外，在为特定应用改进和定制MRE之前，必须从根本上了解MRE中微观结构和宏观行为之间的关系。本项目致力于对磁流变液在有限变形区域中的磁力行为进行建模和表征，以最终了解磁流变液的结构-性能关系。本研究的目标是通过在微观尺度上对代表性体积元(RVE)模型的多物理模拟进行均匀化，建立第一个基于微观结构的磁流变液宏观本构模型。在本研究中，将通过MicroCT获得各种磁流变材料的真实三维微观组织，以建立计算的磁流变液RVE模型。宏观尺度的完整磁力本构模型将通过RVE模型的均匀化来推导和校准。将进行综合实验，并将使用测量的微观尺度变形(通过MicroCT)和宏观尺度(通过数字图像相关(DIC)系统)来分别验证所开发的基于微观结构的RVE模型和宏观尺度模型。这些模型将被应用于一个实际的工程问题，即磁流变橡胶空气弹簧的设计优化。该项目依赖于分析、数值和实验工作的独特组合，它将提供(I)磁流变材料的磁力学实验方案；(Ii)用于磁流变材料的基于微观结构的RVE模型；(Iii)用于磁机械问题的多物理非线性有限元求解器；以及(Iv)适用于任何多物理现象的通用宏观本构模型框架。该项目的成功将对工业界和学术界产生重大的直接影响。

Magnetorheological elastomers (MREs) are multi-phase, multi-functional composite materials with magnetisable particles suspended in a non-magnetic elastomer solid. The mechanical properties of MREs can be reversibly changed and controlled almost instantaneously by altering an externally applied magnetic field. For this reason MREs are regarded as a class of smart materials and hold promise in many industrial applications (e.g., adaptive tuned vibration absorbers, stiffness tuneable mounts, and artificial muscles). However, a generalised constitutive model for MREs is lacking due to the difficulties to model precisely MREs' nonlinear and anisotropic behaviour (including the nonlinear ferroelectric properties of the particles, the nonlinear mechanical response of the matrix, and the anisotropy caused by the material microstructure and the external magnetic field), making it currently difficult to simulate and optimise the design of MRE applications in a virtual environment. Given the importance of computer aided engineering in today's design methodology, this is clearly a significant obstacle preventing widespread exploitation of MREs. Furthermore, a fundamental understanding of the relationship between microstructure and macroscale behaviour in MREs is essential before improving and tailoring MREs for a specific application can be achieved. This project is concerned with modelling and characterisation of the magnetomechanical behaviour of MREs in the finite deformation regime in order to ultimately understand the structure-property relation of MREs. The goal is to develop the first realistic microstructure-based macroscale magnetomechanical constitutive model for MREs via homogenisation of the multi-physics simulation of representative volume element (RVE) model at the microscale.In the proposed research, true 3D microstructures of various MRE materials will be obtained by MicroCT to develop computational magnetomechanical RVE models of MREs. Macroscale complete magnetomechanical constitutive models will be derived and calibrated through homogenisation of the RVE models. Comprehensive experiments will be implemented and the measured microscale deformation (via MicroCT) and macroscale (homogenised) deformation (via Digital Image Correlation (DIC) system) will be employed to verify the developed microstructure-based RVE models and macroscale models respectively. The models will then be applied to a real engineering problem, the design optimisation of the MRE rubber air springs.This project hinges upon a unique combination of analytical, numerical and experimental work and it will deliver (i) magnetomechanical experimental protocols for MRE materials; (ii) microstructure-based RVE models for MRE materials; (iii) a multi-physics nonlinear FEM solver for magnetomechanical problems; and (iv) a general macroscale constitutive modelling framework applicable to any multi-physics phenomena. The successful outcome of this project will have significant direct impact on both industrial and academic communities.