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

Georgia Tech Research Corporation, Atlanta GA

Investigators

Abstract

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.