Design and Structural Optimization in Additive Manufacturing - From Isotropy to Anisotropy

This research aims to investigate ways to combine design and structural optimization with anisotropic considerations for additive manufacturing (AM) of lightweight parts with minimized compliance.
The scope of this PhD encompassed two major themes: numerical analyses and computational modelling as well as experimental testing and manufacturing. The following three objectives will be the subject of this work:

Objective 1: Isotropic topology with orthotropic reinforcement derived from medial axis transformation (MAT)
-Content/Numerical Approach: It is envisaged to develop a novel method which combines continuous fibre reinforcement (C-FR) i.e. an effective fibre trajectory planning with topology optimization in an iterative process under the consideration of AM-specific manufacturing constraints. Preliminary investigations and methods on this topic have been published recently (SFF Symp 2018)
-Experimental Verification: In order to fabricate these novel AM-designs with tailored fibre paths, a custom multi-material 3D printer enabling fibre reinforced AM (FRAM) was developed and will be further improved.
-Potential Applications and Value: This novel approach aims to enhance the performance of AM-parts in terms of stiffness and weight, making them more viable for a wider range of industries. Besides this development towards end-use parts, we seek to gain valuable findings that help streamline the product and development cycles for engineers and designers employing AM processes.
Objective 2: Multiscale modelling of mixed architectures with representative volume elements (RVEs) realizing light multifunctional AM-parts
-Content/Numerical Approach: This objective aims to develop bio-inspired, light, stiff and robust sandwich structures for AM (see Figure 1). The development of a method which effectively combines topology optimization, C-FR and functionally graded cellular structures will be hereby pursued. From a computational point of view this will include multiscale modelling with dissimilar architectures using RVEs to replicate heterogeneous material characteristics.
-Experimental Verification: It is envisaged to employ the above-mentioned custom 3D printer. For the evaluation of the robustness it is intended to conduct for variable loading scenarios.
-Potential Applications and Value: This objective aims to combine the two topics in structural optimization for AM which are currently undergoing intense study, namely topology optimization and the employment of cellular structures. This enables the realization of multi-objective structures for AM, which combine e.g. stiffness and strength (fibre reinforced shell) with improved thermal conduction or impact resistance (cellular structure). Possible application can be found in the automotive, the medical engineering and the aerospace sector.
Objective 3: Mapping functionally graded lattices to specific mechanical performance
-Content/Numerical Approach: The actively researched topic of functionally graded lattices exploits the inherent design freedom of AM for tailored and locally varying material properties. However, in polymer-based AM, certain microstructural grading schemes have not been thoroughly studied yet. For this purpose multiscale modelling approaches using RVEs will be developed helping for a better understanding of these materials and aiding their wider application and adoption.
-Experimental Verification: Among others, our custom multi-material 3D will be employed to manufacture advanced microstructurally and compositionally grading cellular structures. Mechanical tests shall help optimizing the computational model.
-Potential Applications and Value: These findings will help different industries, which are increasingly adopting cellular structures for the design of their products, to better predict and understand the mechanical characteristics of different cell topologies and therefore enable them to fabricate more efficient structures.