Modeling the Large Deformation of Spark Plasma Sintered Polytetrafluoroethylene Under Uniaxial Tension by Phenomenological Approaches

Tensile mechanical characterization was performed on polytetrafluoroethylene (PTFE) to assess how compaction pressure during spark plasma sintering (SPS) influences its properties. Owing to its unique microstructural features, its mechanical behavior exhibits a complex, nonlinear response under external loads. In this study, we employ two phenomenological models—the five‐parameter Mooney–Rivlin and the four‐term Béchir—to replicate the stress–strain curves of PTFE samples sintered at varying compaction pressures during SPS. Although this nonmelting technique overcomes the limitations of conventional methods for densifying highly viscous polymers, it also provides greater control over the microstructure of the sintered material, especially through high heating and cooling rates. Consequently, a significant portion of the amorphous phase can be produced, making the samples nearly incompressible, as confirmed by differential scanning calorimetry measurements (DSC). We evaluate each model's ability to accurately represent the tensile mechanical behavior of the PTFE specimens. We find that there is an inverse correlation between several specific fit parameters of these phenomenological models and the strain hardening obtained from the Haward‐Thackray model in the plastic deformation zone. Our results demonstrate excellent agreement between the experimental data and both phenomenological models, confirming their effectiveness in predicting the nonlinear mechanical behavior of semicrystalline polymers.