Session: 03-08-02: Computational Modeling and Simulation for Advanced Manufacturing

Paper Number: 114142

114142 - Effect of Internal Structure on Warpage in a Large-Scale Additive Manufacturing Process With Bio-Derived Composites 

Large-scale additive manufacturing (AM) often produces parts with unintended deformation and failures during the manufacturing process. The process involves a hot molten polymer deposited on a previously deposited and cooled solidified layer, generating a temperature mismatch between the layers. A long layer time leads to an over-cooled surface on which a new layer is deposited, and therefore, it may result in a weak bonding or debonding between layers, cracking, or warping. A short layer time leads to a high temperature of the structure due to insufficient cooling, and therefore, the structure may not be stiff enough and may collapse during manufacturing. The temperature difference between the previously deposited layer and the new layer being deposited causes thermal contraction mismatches with the different shrinkage rates, generating thermal residual stress between layers. Due to the residual stress, printed structures experience warpage and delamination. Therefore, understanding the heat distribution behavior essential to predict undesired failures. We used biomaterial reinforcement which has been widely used thanks to its sustainability, specific stiffness, and low cost compared with carbon and glass reinforcement. The reinforcement increases the structural stability of the printed part, reducing deformation. However, the challenges of unexpected deformation remain in the utilization of natural fiber reinforcement in the AM process. The goal of this work is to investigate the effect of internal structures (a.k.a., infill patterns) on heat distribution and deformation in the large-scale additive manufacturing system with wood fiber-reinforced polylactic acid. A sequentially coupled thermal-structural analysis was conducted to predict the temperature field and warpage with thermo-mechanical properties, which were measured by a thermo-mechanical analysis test and a dynamic mechanical analysis test. Simulations were performed on a box geometry with three different infill geometries, namely square, hexagon, and triangle lattice geometries. The lattice geometries are optimized for different infill geometries and compared for a same given weight. The optimized box geometry with infill lattice is found to have 67% less weight as compared to the original structure. We printed a box geometry model with three different infill geometries. The toolpath for printing is optimized to be continuous to eliminate unnecessary start and stops that would otherwise lead to higher print times. During the process, temperature data were gathered with an IR camera, and final deformations were measured. The simulation model was verified with the experiments, and the results show a good agreement between predicted and measured temperature profiles and deformations. We applied the developed simulation model to a roof tray with complex geometries for a case study.

Presenting Author: Tyler Smith Oak Ridge National Lab

Presenting Author Biography: Tyler Smith is a technical professional at the Manufacturing Demonstration Facility (MDF), Oak Ridge Manufacturing Laboratory.

Authors:

Eonyeon Jo University of Tennessee, Knoxville
Katie Copenhaver Oak Ridge National Laboratory
Deepak Kumar Pokkalla Oak Ridge National Laboratory
Tyler Smith Oak Ridge National Lab
Uday Vaidya University of Tennessee, Knoxville
Vlastimil Kunc Oak Ridge National Laboratory
Soydan Ozcan Oak Ridge National Laboratory
Seokpum Kim Oak Ridge National Laboratory