No abstract

Additive manufacturing is progressively paving the way for optimised lightweight components that, due to their typically complex shape, would hardly be feasible with traditional production methods. However, the peculiar mechanical properties of additively manufactured materials limit the accuracy of structural analyses. In this research, a strategy for the implementation of thickness dependent anisotropy into finite element shell models is developed by example of laser sintered polyamide. The material behaviour was modelled by fitting parametric functions to experimental data. Subsequently, a routine was developed to map the adaptive material properties into a finite element model of a complex component. Numeric simulations with standard and mapped properties were compared and validated via experiments. Results show that the proposed approach is superior to the conventional method in predicting the structural response. The method is not only applicable to laser sintered polymers but relevant for all structures, where anisotropy and thickness must be considered.

Besides the design freedom offered by additive manufacturing, another asset lies within its potential to accelerate product development processes by rapid fabrication of functional prototypes. The premise to fully exploit this benefit for lightweight design is the accurate structural response prediction prior to part production. However, the peculiar material behavior, characterized by anisotropy, thickness dependency and scatter, still constitutes a major challenge. Hence, a modeling approach for finite element analysis that accounts for this inhomogeneous behavior is developed by example of laser-sintered short-fiber-reinforced polyamide 12. Orthotropic and thickness-dependent Young’s moduli and Poisson’s ratios were determined via quasi-static tensile tests. Thereof, material models were generated and implemented in a property mapping routine for finite element models. Additionally, a framework for stochastic finite element analysis was set up for the consideration of scatter in material properties. For validation, thin-walled parts on sub-component level were fabricated and tested in quasi-static three-point bending experiments. Elastic parameters showed considerable anisotropy, thickness dependency and scatter. A comparison of the predicted forces with experimentally evaluated reaction forces disclosed substantially improved accuracy when utilizing the novel inhomogeneous approach instead of conventional homogeneous approaches. Furthermore, the variability observed in the structural response of loaded parts could be reproduced by the stochastic simulations.