Institute for Applied Materials – Materials Science and Engineering

Additively manufactured foam sandwich structures - a novel approach for generative production and characterization of foam-based, three-dimensionally graded materials for lightweight construction

M.Sc. Anselm Heuer

3D printed components are usually not printed with a complete fill inside to save material and printing time. This makes it possible to produce porous components without much effort. However, this porosity consists of large cavities (macroscopic porosity) compared to fine cellular foams and smaller cavities under the printing resolution cannot be realized. By foaming a plastic with a chemical or physical blowing agent such small cavities or fine cellular foams (microscopic porosity) could be produced. A combination of these two processes of porosity generation could produce completely new porous components (macroscopic and microscopic porosity) with new properties. For example, it would be possible to produce graded foamed and only locally foamed structures. The application range of the "3D printing" manufacturing process is thus extended to complex graded foam structures.

Motivation

  • Production and characterization of complex components with graded foam structure.
  • Investigate observed shrinkage compensation.
  • Investigate possible influence on the interface between the printed lines.
  • Identify fields of application in medical technology and for filters and membranes.

Procedure

  • Using suitable material combinations (plastic and chemical blowing agent) and suitable process parameters, simple in-situ foamed 3D printed samples are produced (machine Freeformer).
  • Characterization of the foam structures by testing the mechanical properties and evaluation of µCT investigations. Exact determination of the process influencing parameters on the foam structure.
  • Measuring the interface strength between printed lines.
  • Investigation of the shrinkage of a semi-crystalline plastic. Achieving shrinkage compensation through foaming.
  • Production of complex components with graded foam structure.
  • Designing and manufacturing demonstrators for applications in medical technology and for filters and membranes. Simple testing of these demonstrators for functional performance.

Methods

  • Microscopic investigation of "drop chains".
  • Measurement of density with the measuring principle of Archimedes.
  • Design of experiments for the determination of process parameters.
  • Tensile, compression and bending tests.
  • µCT investigation to determine the macroscopic and microscopic porosity.
  • Separation of the macroscopic and microscopic porosity by algorithms.
  • Light microscopy, scanning electron microscopy.