Incorporating Recycled Sheet Molding Compound Waste Into Polypropylene Part Manufacturing: Experimental Characterization and Mechanical Modeling

ABSTRACT Waste thermoset composites are being promoted as a potentially sustainable material source, although their structural capabilities remain underexploited. This study investigates the exclusive use of micronized recycled sheet molding compound (SMC) powder, without compatibilizers or coupling agents, as reinforcement in polypropylene (PP) composites. PP composites containing 10, 20, and 30 wt.% SMC were produced by twin‐screw compounding followed by injection molding. Thermogravimetric analysis confirmed the actual SMC content in the PP matrix, ensuring process consistency. Comprehensive thermal, chemical, rheological, and mechanical tests were performed to assess the SMC influence. Results show that the PP crystallinity is nearly unaffected by SMC addition (73–76 J g −1 ), while melt viscosity rises by up to 32% at low‐shear rates without impairing processability. Adding 30 wt.% SMC increases tensile and flexural stiffness by 70% and flexural strength by 6%, but decreases tensile strength by 14% and impact energy absorption by 50%. Unlike prior studies based on compatibilized systems, this work focuses on untreated micronized SMC in PP and directly calibrates predictive modeling on experimental data. Beyond SMC waste recycling, the study demonstrates the ability to predict the mechanical behavior of heterogeneous recycled composites using a Perzyna‐type elasto‐viscoplastic constitutive law, showing a high correlation between simulations and experiments.