This study examines the effect of consolidation force during Automated Fiber Placement (AFP) on the mechanical and fracture behavior of carbon fiber-reinforced polymer composites with different stacking sequences. Unidirectional (UD), cross-ply (CP), and quasi-isotropic (QI) laminates are fabricated using consolidation forces of 300 N and 600 N. Tensile, mode-I, mode-II, and short beam shear (SBS) tests are conducted, complemented by in-situ acoustic emission (AE) analysis to monitor real-time damage progression. Higher consolidation forces enhance tensile strength, particularly in QI laminates, resulting in a 12% increase, while Young's modulus remains unaffected for UD and CP laminates. Mode-I interlaminar fracture toughness improves by 16% for UD and CP laminates under higher consolidation forces, while QI laminates exhibit minimal change. Mode-II tests reveal that QI laminates demonstrate superior delamination resistance, whereas UD composites show lower toughness due to rapid crack propagation. AE analysis indicates that QI laminates have higher cumulative acoustic counts and energy, reflecting increased damage accumulation and energy dissipation under both mode-I and mode-II loading conditions. Additionally, AE data highlight enhanced interfacial bonding, supported by peak-frequency rates and AE energy levels. This study emphasizes the critical roles of fiber orientation and consolidation force in determining the mechanical performance and damage behavior of AFP-manufactured composites. By integrating in-situ AE techniques, it provides insights into optimizing AFP processes for improved composite performance.

Homogeneous dispersion of graphene into thermoplastic polymer matrices during melt-mixing is still challenging due to its agglomeration and weak interfacial interactions with the selected polymer matrix. In this study, an ideal dispersion of graphene within the PA66 matrix was achieved under high shear rates by thermokinetic mixing. The flow direction of graphene was monitored by the developed numerical methodology with a combination of its rheological behaviors. Graphene nanoplatelets (GNP) produced from waste-tire by upcycling and recycling techniques having high oxygen surface functional groups were used to increase the compatibility with PA66 chains. This study revealed that GNP addition increased the crystallization temperature of nanocomposites since it acted as both a nucleating and reinforcing agent. Tensile strength and modulus of PA66 nanocomposites were improved at 30% and 42%, respectively, by the addition of 0.3 wt% GNP. Flexural strength and modulus were reached at 20% and 43%, respectively. In addition, the flow model, which simulates the injection molding process of PA66 resin with different GNP loadings considering the rheological behavior and alignment characteristics of GNP, served as a tool to describe the mechanical performance of these developed GNP based nanocomposites.