A multi-objective investigation of warpage and mechanical performance in FDM-printed thermoplastic composites

Warping remains a critical challenge in fused deposition modeling (FDM) of thermoplastic composites, leading to dimensional inaccuracies and compromised mechanical properties in printed parts. Existing studies have predominantly examined individual factors that affect warpage, such as infill specifications and printing orientation, without a comprehensive assessment of their combined effects. This study addresses this gap by employing a transient thermomechanical simulation approach in Digimat-AM, which integrates material crystallinity evolution, fiber orientation effects, and toolpath-dependent thermal history to enhance warpage prediction accuracy. A short carbon fiber-reinforced polyamide 12 composite was selected as the material system due to its complex thermal behavior, including the negative thermal expansion coefficient of carbon fibers. An unmanned aerial vehicle (UAV) camera holder was used as a case study, where the effects of the infill density, the infill pattern, the printing orientation, and the raster angle on warpage and mechanical performance were systematically analyzed. The high-fidelity simulation method in Digimat-AM was utilized to predict warpage, while experimental validation was performed through tensile and bending tests. Analysis of variance was applied to optimize the process parameters. The results demonstrated that a 90% infill density, a triangular infill pattern, a flat printing orientation, and a 90° raster angle significantly reduced warpage, achieving a deviation angle of as low as 0.04°. Furthermore, the combination of 90% infill density, concentric infill pattern and 90° raster angle improved tensile strength (45.58 MPa) and stiffness (2.57 GPa), confirming improved mechanical integrity.