Collaborative Research: Design of Active Composites Enabled by 3D Printing

该奖项支持建立3D打印活性复合材料设计方法的研究。在这些材料中，成分相互作用使得由复合材料制成的物体在外部刺激（如温度变化）下改变其形状。通过3D打印工艺，可以制造具有复杂内部布局的复合材料。这种复合材料最初被打印为平面，经过热机械处理后呈现3D形状，并在激活后变形成另一种3D形状。3D打印活性复合材料为医疗保健，生物医学，航空航天和汽车应用中的广泛工程问题提供了新的解决方案。例如，活性复合材料将使新型软体手术机器人成为可能，其初始形状适合插入人体，然后将其展开成所需的形状以辅助外科手术。目前还没有系统地设计这些复合材料的工具。这项研究涉及几个学科，包括数学、力学和计算机科学。这种设置将为参与本项目的学生提供一个刺激的环境，并扩大代表性不足的群体在研究中的参与。外展活动将把3D打印的兴奋带入K-12教室。活性复合材料由嵌入弹性基体中的玻璃状聚合物组成。玻璃聚合物的机械性能对温度的依赖性产生了一种形状聚合物效应。在3D打印过程中，聚合物相的性能取决于复杂的加工条件。本构响应将被描述为温度相关和各向异性的非线性粘弹性。热-力学响应实验将支持本构模型的发展。设计方法将非线性材料模型集成到多材料拓扑优化方法中。同时优化玻璃状聚合物包裹体的位置和形状以及确定编程载荷的参数。因此，由于热机械处理和激活，复合材料假定一组目标形状。材料界面的几何形状将用水平集方法来描述。用扩展有限元法的广义公式来预测打印复合材料物体的响应。为了考虑制造限制，例如打印机分辨率的限制，将开发控制3D材料布局中最小特征尺寸的限制。优化问题将采用基于梯度的算法进行求解，并采用伴随法计算目标约束和设计约束的梯度。实验将用于验证设计方法。

This award supports research in establishing a design methodology for 3D printed active composites. In these materials constituents interact such that an object made of the composite alters its shape upon an external stimulus, such as a temperature change. With a 3D printing process composites with complex internal layouts can be manufactured. The composite is printed as an initially flat sheet which takes on a 3D shape after thermo-mechanical treatment, and deforms into yet another 3D shape upon activation. 3D printed active composites open the door for new solutions to a broad class of engineering problems in healthcare, biomedical, aerospace, and automotive applications. For example, active composites would enable novel soft surgical robots whose initial shape is suited for insertion into the human body and which are then deployed into a desired shape to assist a surgical procedure. Currently there exist no tools for systematically designing these composites. This research involves several disciplines, including mathematics, mechanics, and computer science. This setting will provide a stimulating environment for students who will participate in this project and broaden participation of underrepresented groups in research. Outreach activities will bring the excitement of 3D printing into K-12 classrooms.The active composite consists of glassy polymers embedded in an elastomeric matrix. The temperature dependence of the mechanical properties of glassy polymers creates a shape polymer effect. The properties of the polymer phases depend on complex processing conditions during 3D printing. The constitutive response will be described as temperature-dependent and anisotropic nonlinear viscoelastic. Experiments on the thermomechanical response will support the constitutive model development. The design methodology will integrate the nonlinear material models into a multi-material topology optimization approach. The location and shape of glassy polymer inclusions as well as parameters defining the programming loads will be optimized simultaneously. Consequently, the composite assumes a set of target shapes due to thermo-mechanical treatment and upon activation. The geometry of the material interfaces will be described by a level set method. The response of the printed composite objects will be predicted by a generalized formulation of the extended finite element method. To account for manufacturing constraints, such as limitations in printer resolution, constraints for controlling the minimum feature size in 3D material layouts will be developed. The optimization problem will be solved by a gradient-based algorithm, computing the gradients of objective and design constrains by the adjoint method. Experiments will be employed for validation of the design methodology.