Processing, thermal history and mechanical performance of recycled PP + 30 wt% glass fiber in large-format additive manufacturing (LFAM)

Fused Granular Fabrication (FGF) is an increasingly utilized technique in Large Format Additive Manufacturing (LFAM). In this process, the quality of printed parts is directly influenced by printing parameters and inter-layer temperature. This study examines the influence of these factors on the printing quality of objects fabricated from recycled polypropylene reinforced with 30 wt% glass fiber (PP + 30 % GF). A predictive model was developed to analyze the effects of nominal layer height, deposition speed, and extruder rotation on actual layer height, contact width, thickness, and flexural strength in both longitudinal and transverse directions, using a Design of Experiments (DOE) approach. Following this, the inter-layer temperature distribution across fifteen printed layers was simulated using Ansys DED software and validated through thermal camera measurements. The analysis was then extended to a 100-layer model to predict inter-layer temperature evolution. Finally, the inter-layer temperature at the 20th layer was analyzed for all DOE-fabricated samples and compared with the crystallization temperature to assess bonding quality under thermally stabilized conditions.