Multidisciplinary Design of Microvascular Composites Based on a Hierarchical Approach

受生物体循环系统的启发，微血管复合材料是一种新型的纤维增强聚合物，它具有嵌入的微通道网络。这项工作的重点是通过这些微通道循环冷却剂，以允许在高温条件下使用复合材料组件，远远超出其传统用途。这些材料的设计自然导致了一个多学科的优化问题：从热学的角度来看，可以通过增加流动冷却剂的微通道的数量来实现更有效的主动冷却。但从结构角度来看，每一条通道都代表一个小空洞，可能会导致应力集中，对复合材料的刚度和强度产生负面影响。尽管作为该项目的一部分而开发的多学科计算设计方法侧重于高温应用，但微血管复合材料正被考虑用于广泛的多学科应用，包括新的电学、电磁或传感性能。计算和实验相结合的研究项目将为两名研究生和一名暑期本科生研究助理提供独特的多学科培训经验。该项目将开发的分层计算设计方法将在非均质材料的高效和准确建模方面取得重要进展，并在制定稳健的基于梯度的形状优化方法方面取得重要进展，该方法避免了与传统有限元方法相关的网格扭曲问题。建模工作的核心是一种等几何界面丰富的广义有限元方法(IIGFEM)，该方法允许使用与嵌入的微通道网络和复合材料微观结构不一致的有限元离散来模拟微血管复合材料的热和结构。然后，基于与嵌入网络的热性能和流动效率及其对微血管复合材料结构特性的影响相关的一组目标函数和约束，将IIGFE与分级的、基于梯度的形状优化方案相结合来计算微通道网络的最佳形状。这种自上而下的设计方法建立在最先进的计算和实验工具基础上，依赖于热力模型和长度尺度的层次结构，提供了一种有效的方法来处理具有多个、相互冲突的、多学科的目标函数和约束的设计过程的规模和复杂性。

Inspired by the circulatory systems present in a wide range of living organisms, microvascular composites are a new class of fiber-reinforced polymers that possess a network of embedded microchannels. The focus of this work is placed on circulating a coolant through these microchannels to allow for the use of composite components in high temperature conditions, well beyond their traditional use. The design of these materials naturally leads to a multidisciplinary optimization problem: from a thermal point of view, more efficient active cooling can be achieved by multiplying the number of microchannels in which flows the coolant. But from a structural point of view, every channel represents a small void that may lead to stress concentration and negatively affect the stiffness and strength of the composite. Although the multidisciplinary computational design method to be developed as part of this project focuses on high temperature applications, microvascular composites are being considered for a wide range of multidisciplinary applications, including new electrical, electromagnetic or sensing properties. The combined computational and experimental research project will provide a unique multidisciplinary training experience for two graduate students and one summer undergraduate research assistant.The hierarchical computational design method to be developed in this project will lead to important advances in the efficient and accurate modeling of heterogeneous materials, and in the formulation of a robust gradient-based shape optimization approach that eludes issues associated with mesh distortion often associated with conventional finite element methods. At the heart of the modeling effort is an isogeometric interface-enriched generalized finite element method (IIGFEM) that allows for the thermal and structural modeling of microvascular composites with finite element discretizations that do not conform to the embedded microchannel network and the composite microstructure. The IIGFEM is then combined with a hierarchical, gradient-based shape optimization scheme to compute the optimal shape of the microchannel network based on a set of objective functions and constraints associated with the thermal performance and flow efficiency of the embedded network, and its impact on the structural properties of the microvascular composite. Building on state-of-the-art computational and experimental tools, this top-down design method, which relies on a hierarchy of thermo-mechanical models and length scales, offers an efficient approach to tackle the size and complexity of a design process characterized by multiple, conflicting, multi-disciplinary objective functions and constraints.