Experimental investigation of low-velocity impact response in PP/date palm fiber bio-composites reinforced with compatibilizer and impact modifier

This study experimentally and statistically investigates the low-velocity impact performance of polypropylene (PP) composites reinforced with date palm fibers (DPF). Composite specimens were prepared through melt compounding followed by compression molding and tested under instrumented drop-weight impact according to ASTM D7136. The effects of fiber content (10–30 wt.%), PP-g-MA compatibilizer (1–5 wt.%), and impact-modifying masterbatch (1–5 wt.%) were evaluated using a Box–Behnken design. Quadratic regression models were developed for maximum impact force (Fₘₐₓ) and energy absorption (Eₐ), showing strong agreement with experimental results (R² = 0.977 and 0.957, respectively). Statistical analysis indicated that the masterbatch content was the most influential parameter (p < 0.01), leading to up to a 35% improvement in energy absorption and a 22% increase in peak impact force. The best performance was obtained at 18 wt.% fiber content, where the composite exhibited the highest energy absorption and a notable increase in peak force, reflecting an effective balance between stiffness and toughness. Scanning electron microscopy (SEM) revealed enhanced fiber–matrix adhesion, fewer interfacial voids, and more ductile fracture surfaces at this composition. The main energy dissipation mechanisms included fiber pull-out, matrix fibrillation, and plastic deformation. Overall, the combined experimental and statistical approach presented in this study provides practical guidance for designing sustainable PP/DPF composites with superior impact energy absorption suitable for semi-structural and automotive applications.