Structured Materials

Digital fabrication offers precise control over the fine-level structure of materials. By shaping a material's structure, we can controll its macro-mechanical properties. Our research addresses some of the fundamental challenges that arise when designing such structured materials:

  • understanding and navigating the material space induced by structural subspaces
  • designing macromechanical properties in the presence of constraints imposed by the material or fabrication process, and 
  • optimizing structural properties in the presence of aesthetic design constraints.

Structured Sheet Materials

Mechanical Characterization of Structured Sheet Materials
C. Schumacher, S. Marschner, M. Gross, B. Thomaszewski
ACM Transactions on Graphics (Proc. ACM SIGGRAPH 2018)
PDF Video Project

We propose a comprehensive approach to characterizing the mechanical properties of structured sheet materials, i.e., planar rod networks whose mechanics and aesthetics are inextricably linked. We establish a connection between the complex mesoscopic deformation behavior of such structures and their macroscopic elastic properties through numerical homogenization. Our approach leverages 3D Kirchhoff rod simulation in order to capture nonlinear effects for both in-plane and bending deformations. We apply our method to different families of structures based on isohedral tilings — a simple yet extensive and aesthetically interesting group of space-filling patterns. We show that these tilings admit a wide range of material properties, and our homogenization approach allows us to create concise and intuitive descriptions of a material’s direction-dependent macromechanical behavior that are easy to communicate even to non-experts. We perform this characterization for an extensive set of structures and organize these data in a material browser to enable efficient forward exploration of the aesthetic-mechanical space of structured sheet materials. We also propose an inverse design method to automatically find structure parameters that best approximate a user-specified target behavior.

Structured Silicone

MetaSilicone: Design and Fabrication of Composite Silicone with Desired Mechanical Properties
J. Zehnder, E. Knoop, M. Bächer, B. Thomaszewski
ACM Transactions on Graphics (Proc. ACM SIGGRAPH Asia 2017)
PDF Video

We present a method for designing and fabricating MetaSilicones—composite silicone rubbers that exhibit desired macroscopic mechanical properties. The underlying principle of our approach is to inject spherical inclusions of a liquid dopant material into a silicone matrix material. By varying the number, size, and locations of these inclusions as well as their material, a broad range of mechanical properties can be achieved. The technical core of our approach is formed by an optimization algorithm that, combining a simulation model based on extended finite elements (XFEM) and sensitivity analysis, computes inclusion distributions that lead to desired stiffness properties on the macroscopic level. We explore the design space of MetaSilicone on an extensive set of simulation experiments involving materials with optimized uni- and bi-directional stiffness, spatially-graded properties, as well as multi-material composites. We present validation through standard measurements on physical prototypes, which we fabricate on a modified filament-based 3D printer, thus combining the advantages of digital fabrication with the mechanical performance of silicone elastomers.

Aesthetically-Constrained Subspaces

Stenciling: Designing Structurally-Sound Surfaces with Decorative Patterns
C. Schumacher, B. Thomaszewski, M. Gross
Symposium on Geometry Processing (SGP),  2016
PDF   Video  

We present a novel method to design shells with artistic cutouts in a manner that produces a stable final result. The process of stenciling, removing material with a fixed shape, is a particularly appealing way to introduce a decorative pattern into the design of architectural structures, furniture, or household objects. However, removing material can easily weaken an object to the point where its integrity is compromised, while purely functional distributions of cutouts lack the desired aesthetic component. We tackle this problem by combining aesthetics, stability, and material efficiency in an optimization that determines the distribution and scaling of these stencils in a way that complies as much as possible with both pattern and stability objectives. We demonstrate the capabilities of our system on examples from architecture, furniture design, and decorative items, and show how user interaction can be integrated to guide the aesthetics of the final result.