Topological optimization of structural components for thermoplastic 3D printing

The research work explains suitable materials and the processes to optimize these materials for 3D printing of building components. 3D printing is a technological innovation that has been introduced in the construction industry for quite some time now. One of the major outcomes of using 3D printing in construction is that it allows freedom of design and ample margin in printing complex load bearing components using the medium of ‘robotics’. For this PhD research, a wide range of polymers were tested to find their orthotropic materials properties. The polymer materials used in this research are polylactic acid, acrylonitrile butadiene styrene, recycled polyethylene terephthalate glycol and carbon fiber polyethylene terephthalate glycol. These materials were tested to find if they are viable to be used in developing loadbearing construction components via 3D printing. In addition to the above mentioned, part of the research included topology optimization, removing unnecessary materials to ensure optimum performance. An important aspect of this research is optimizing the topology of building parts subjected to volume constraints. From the above mentioned materials, polylactic acid and acrylonitrile butadiene styrene were used to 3D print elliptical hollow sections, which were then tested under ’compression’. The test results revealed that the elliptical hollow sections of polylactic acid exhibited stiffness, whereas those of the acrylonitrile butadiene styrene (ABS) displayed gradual failure. The results suggested a potential usage of these polymers in a light load-bearing context (purlins, rafters etc). Furthermore, two case studies were conducted to investigate topology optimization; one focusing on truss element and the other on tubular connection. The truss element was modelled in Abaqus (Abaqus, 2020) and tubular connection was initially modelled in Rhino (McNeel, R. & Associates. 2010) before being imported into Abaqus 4 (Abaqus, 2020) for topology optimization, aimed at reducing volume. A number of trials were run to investigate the effects of boundary conditions and loading patterns, identifying areas where material was not necessarily needed. The trials deduced that the material was minimised in low stress areas and retained in high stress areas. The selected boundary conditions and loading patterns for truss element and tubular connection were found appropriate to reduce 70 % of the volume from initial design. The research concluded that, this process will pave a way for using designs with optimized topologies, resulting in reduced material consumption and associated carbon emissions with good performance.