Beyond rapid prototyping – from 3D to 4D printing
Prof. Bodo Fiedler
Hamburg University of Technology
Additive manufacturing is well established for rapid prototyping applications. However, since the peak of inflated expectations in Gartner’s hype cycle for emerging technologies in 2012, there has been a disillusionment. We present advantages and limitations of the current technologies as well as our experience and ideas how to use additive manufacturing in more sophisticated applications.
In aviation and aerospace lightweight structural applications, lattice materials show potential. They exploit the possibilities of complex designs with additive manufacturing. Their mechanical properties can be scaled by the relative density of the unit cells and adapted to the local requirements given by the load paths. Thus, weight and consecutively the fuel consumption can be reduced which leads to economic and ecological benefits. A geometrical and mechanical characterization of lattice structures was performed for Ti-alloy (SLM) and UV curing thermoset (SLA). To gain further insights into the failure process, we use finite element simulations with progressive damage. The load introduction and especially imperfections often inherent in additive manufacturing processes strongly influence the mechanical performance. These are incorporated in the material models for the design process by stochastic methods.
In addition, functional integration in the additive manufacturing process - 4D printing - is a promising field. The application of additive manufactured tailor-made functional structures with integrated conductors and sensors for process monitoring and improvement in chemical and biochemical reactors is presented. Functional materials like stimuli responsive hydrogels are used to control reactions in smart reactors.
Also carbon nanoparticle modified polymers are applied for structure integrated sensing of strain and temperature exploiting the piezo resistive effect. This requires multi material printing which is currently only easy to implement in extrusion and jetting based manufacturing technologies. However, these technologies struggle with anisotropy or expensive and hazardous UV curing agents. Thus, a new material system based on a hot melt thermoset is developed. It overcomes the anisotropy issues by cross-linking and prints with low cost fused filament fabrication printers (FDM). Finally, our efforts to implement 3D printing in teaching are shown with a hands-on project for first year students.