Joël Chapuis


Last Name

Chapuis

First Name

Joël

ORCID

0000-0002-4209-3466

Organisational unit

03954 - Shea, Kristina / Shea, Kristina

Filters

2022 - 202510
Reset filters

Search Results

Publications 1 - 10 of 10
  • Active Additively Manufactured Machines
    Item type: Doctoral Thesis
    Chapuis, Joël (2025)
    Active materials inherently change their shape, properties and functionality in response to an environmental stimulus. When integrated into additively manufactured structures, also known as 4D printing, these materials enable the creation of versatile engineering systems with complex and tunable behavior. Despite recent advances in 4D printing, it has not found significant applications in additively manufactured machines and machine components. This limited adoption arises from several factors, including reliability concerns common to many AM parts, difficulties in predicting complex material and shape changes, manual shape programming, the complexity of tuning materials at a voxel level and an overreliance on manual, case-specific design methods. This thesis aims to systematically explore how the 4D printing process, active materials and simulation can be used to create novel, predictable and reliable integrated machines. The thesis covers three core components commonly associated with any machine: mechanisms, structural elements and control components. Key insights are developed through a combination of mechanical principles, material knowledge, multi-material additive manufacturing and computational design methods. First, focusing on mechanisms for machines, a direct 4D printing process on a fused filament fabrication (FFF) system combined with numerical simulations is used to create a reliable and highly tunable polymer wave spring based on shape memory polymers (SMPs). The springs exhibit exceptional performance under cyclic loading, reaching 10'000 cycles without failure. After plastic deformation due to extended cyclic loading, the springs can be redeployed to recover their original mechanical properties through cold programming, significantly extending their lifespan. Active materials in additively manufactured machines directly influence their structural performance, particularly when the materials activate across multiple time scales and temperatures. To address challenges related to stress concentrations and complex loading, such as hysteresis, in structural elements, the properties of architected voxelated digital materials consisting of SMPs and their simulation is explored. Percolation theory and an efficient mesoscale material representation are used to predict the behavior of tuned, stochastic voxelated digital materials across multiple length and time scales, achieving a 99.85% reduction in data points in a machine damper case study. The inclusion of active materials in machines further creates the unique opportunity of exploiting passive control and energy harvesting mechanisms. This concept is demonstrated through a passively controlled shape memory alloy (SMA) solar tracker capable of collecting 99% of the available total energy in a continuous tracking scenario. It is driven entirely by an external heat stimulus and builds upon principles commonly associated with solid-state heat engines. In addition, a sequentially deploying multi-material SMP structure is used to show programmed passive control across a temperature spectrum. While some of the proposed concepts are partially limited by current additive manufacturing (AM) processes and materials, the generality of both the underlying principles and the computational methods makes them directly applicable to future advances in materials science and fabrication technologies. As such, the findings in this thesis provide key insights into how 4D printing and active materials, in general, can be integrated into additively manufactured machines and developed towards industrial applications.
  • EDACFEM: A linear truss and beam solver in MATLAB
    Item type: Journal Article
    Chapuis, Joël; Wirth, Marc; Walker, Andreas; et al. (2024)
    SoftwareX
    The on-demand design of metamaterials such as lattices and bar structures is typically approached using computational methods due to their inherent complexity. An indispensable element of structural design is a reliable and easy to use FE simulation environment, which in turn not only benefits the design of underlying structures, but also, through easy customization and integration, propels the design of computational methods themselves. In response, this work provides a linear truss and beam FE simulation environment written in MATLAB. The simulation environment supports linear truss elements, Euler-Bernoulli besam elements, and Timoshenko beam elements. It further supports the introduction of self-weight and local truss buckling analysis. A variety of input methods are supported, these are specifically tailored towards simplifying the integration of the FE simulation environment in numerical optimization schemes. With this environment, researchers and design practitioners can easily simulate the mechanical response of complex bar structures without the need for interfacing with commercial FE software through cumbersome Application Programming Interfaces (APIs).
  • Mechanical properties of topological metamaterials
    Item type: Journal Article
    Chapuis, Joël; Lumpe, Thomas S.; Shea, Kristina (2022)
    Extreme Mechanics Letters
    Recent advances in physics and engineering have led to the discovery of behavioral correlations between thermal, electromagnetic, optical, quantum and classical mechanical metamaterial systems. Of particular interest for the development of novel metamaterial properties is topological polarization, a new mapping established between quantum mechanical topological insulators and mechanical systems. Although recent research has shown many properties of polarized regions in metamaterials, the relationship between the topological effects, force concentration along domain boundaries, and mechanical properties of polarized lattices has found little attention. Further, current findings are also limited to linear continuous boundary regions. Here, we show how the hexagonal Kagome lattice and square lattice in their polarized state can concentrate axial forces along non-linear boundary regions and how the resulting mechanical properties depend on both the direction of the external loading and the magnitude of the nodal displacements used to polarize the given lattices. The results show that the mechanical properties of polarized lattices are primarily informed by the switch from a stretch-dominated to a bending-dominated state during polarization, but also by the increasing force concentration in the domain boundaries. These findings enable the design of complex topological lattices with predetermined concentration behavior while also accounting for changes in the overall mechanical properties.
  • Thermo-Viscoelastic Laminate-Based FE Modelling of Fused Filament Fabrication Direct 4D Printing
    Item type: Other Conference Item
    Chapuis, Joël; Shea, Kristina (2023)
  • Thermo-viscoelastic laminate-based finite element modeling of fused filament fabrication direct 4D printing
    Item type: Journal Article
    Chapuis, Joël; Teufen, Gian; Shea, Kristina (2025)
    Smart Materials and Structures
    Recent advances in fused filament fabrication direct 4D printing necessitate new, accurate modeling approaches to computationally predict the programmed shape change and temperature-dependent mechanical properties of direct 4D printed designs. In this paper, a thermo-viscoelastic, laminate-based finite element modeling approach is proposed to meet this need. The model enables the simulation of the deployment and the mechanical characterization of thin, direct 4D printed structures in one simulation. Unlike conventional modeling approaches based on thermal expansion alone, the model introduces a pre-strain in the material model during model initialization. This creates realistic shape memory behavior during deployment based on a modified, generalized Maxwell model and enables the simulation of subsequent shape memory cycles. The approach is validated using several benchmark examples, including a sequentially deploying, multi-material bilayer to demonstrate the generality of the method and a direct 4D printed wave spring to illustrate a potential application. The method can predict the activation temperatures of the sequentially deploying bilayer to within 2 ◦C of the mean experimental values and the wave spring’s shape and response force to within one standard deviation of the mean experimental values. The predictive simulation of the time-temperature dependent, direct 4D printed shape changing behavior enables designers to gain new, significant insight into the structural performance of direct 4D printed designs and to systematically explore the design space as well as material and manufacturing process interactions.
  • Computational Design of 4D Printed Tunable Pneumatic Valves
    Item type: Other Conference Item
    Chapuis, Joël; Shea, Kristina (2022)
  • Inverse design of stochastic, voxelated thermo-viscoelastic digital materials
    Item type: Journal Article
    Wirth, Marc; Chapuis, Joël; Kristina Shea (2025)
    Nature Communications
    Polymer material jetting enables the fabrication of voxelated, multi-material structures with material control at the microscale. However, current work often neglects viscoelastic effects and designing voxelated digital materials remains challenging due to the complexity of the vast design freedom and intractability of efficiently modeling macroscale voxel structures. We present an efficient representation of stochastically mixed, voxelated digital materials and develop a generalized viscoelastic temperature-dependent material model to design and simulate digital materials mixed from two constituent polymers. The material model is based on an extended percolation theory considering frequency and temperature. An artificial neural network is trained on the material model to directly estimate target material behavior given arbitrary non-linear, user requirements. The approach is validated using two case studies requiring tailored, non-linear material behavior: a personalized wrist orthosis and a machine damper. These show the newly unlocked possibilities for the design and fabrication of tuned, stochastic digital materials.
  • 5-Axis, Direct, 4D Printed Human-Machine Interfaces
    Item type: Other Conference Item
    Chapuis, Joël; Shea, Kristina (2024)
  • Direct 4D Printing of a Deployable Polymer Wave Spring
    Item type: Conference Paper
    Chapuis, Joël; Widmer, Andrin; Shea, Kristina (2022)
    ASME 2022 International Design Engineering Technical Conferences and Computers and Information in Engineering Conference. Volume 3A: 48th Design Automation Conference (DAC)
    4D printing is now commonly defined as a targeted evolution of a 3D printed structure to change its shape, properties, and functionality over time. In direct 4D printing this targeted evolution is embedded in the structure during the 3D printing process. A heat stimulus can be used to trigger a transition between two states of a printed shape memory polymer. 3D and 4D printing have greatly expanded the design space of a variety of engineering parts. However, 3D printed parts often show anisotropic behavior due to layering, especially when using fused filament fabrication. Here, it is shown how direct 4D printing on a fused filament fabrication system can be used to create deployable polymer wave springs. By introducing a pattern of multimaterial bilayer actuators into the wave spring, it can be printed flat and deployed to a designed spring shape through a thermal stimulus. This method eliminates the typical layering issues found in 3D printed springs due to printing at angles. Additionally, it reduces the print time and support material consumption. These findings show the great potential of direct 4D printing on 3D printers using fused filament fabrication to create functional, 4D printed components with complex geometry, such as polymer springs.
  • Redeployable, 4D Printed Wave Spring Actuators
    Item type: Journal Article
    Chapuis, Joël; Shea, Kristina (2023)
    Materials & Design
    Wave springs are a novel type of axial compression spring that offer complete axial load transmission and a significant free height reduction when compared to coil springs. In this paper, it is shown that direct 4D printing using bilayers on a fused filament fabrication system can be used to create deployable, polymer wave springs that do not suffer from layering effects, as is common in other cyclically loaded additively manufactured parts. Bilayer actuators enable a flat print configuration and subsequent deployment by a thermal stimulus that then aligns the layers in the direction of the wave in the spring. Due to this, the springs exhibit exceptional performance under cyclic loading, reaching 10⁴ cycles without failure. After plastic deformation caused by extended cyclic loading, the springs can be redeployed to recover their original mechanical properties using cold programming. These findings show the great potential of direct 4D printing in fused filament fabrication to create functional, 4D printed components with complex geometry and greatly increased lifespan compared to conventional 3D printed parts. The presented approach to compression spring fabrication further provides a standard component that enables the design of highly integrated, monolithically printed, and tunable mechanical systems.
Publications 1 - 10 of 10