Interlayer adhesion in Large Format Additive Manufacturing of glass fiber reinforced ABS structures

Large Format Additive Manufacturing (LFAM) is a promising technology for the rapid production of molds for high-performance composite parts in aerospace and automotive applications. Using ABS reinforced with short glass fibers (20% by weight) as granules improves production rates and mechanical performance. However, interlayer adhesion remains a major challenge, as the interface between layers is typically the weakest point in printed structures. This study examines the effects of three printing parameters on interlayer adhesion: time per layer ($t_L$), nozzle temperature ($T_N$), and extrusion factor ($f_e$). The ABS/20GF composite is first characterized to determine its thermal and physical properties. An infrared camera monitors temperature evolution during printing, and tensile tests with loads applied perpendicular to the printing direction evaluate mechanical performance. Microstructural analysis reveals fracture mechanisms between layers. Results show that interlayer adhesion improves with shorter $t_L$ and higher $T_N$ and $f_e$ values. Thermal monitoring indicates a strong correlation between enhanced strength and reduced temperature gradients between layers, enabling better polymer chain mobility and bonding. ANOVA analysis identifies $t_L$ and $f_e$ as statistically significant factors influencing interlayer adhesion. These findings provide valuable insights for optimizing LFAM process parameters to enhance the structural integrity of fiber-reinforced thermoplastic components.