Analysis of the in-tension mechanical behavior of 3D-printed continuous fiber-reinforced thermoplastic composite laminates

This study presents a comprehensive analysis of the in-plane mechanical behavior in tension exhibited by 3D-printed continuous fiber-reinforced thermoplastic composite laminates based on a thermoset-thermoplastic bi-matrix material (CFTSTP). The investigation explores the key factors influencing the tensile properties of these advanced materials, offering valuable insights for their use in engineering structures. This relatively new 3D printing concept enables fabrication of functional parts with complex geometries and spatial reinforcement. Like additive manufacturing (AM), this technology faces challenges such as voids and defects. Another important aspect is the variation between the fiber content in the filament and the final printed part, which can decrease from 60 to about 20. The experimental mechanical properties of 3D ply composite specimens in tensile (longitudinal and transverse) and in-plane shear are studied, along with cross-ply (CP) and quasi-isotropic (Qiso) laminates. Hourglass-shaped specimens are used to maximize load-bearing capacity and prevent premature failure near the grips. In all tests, strain fields are obtained using the digital image correlation (DIC) method. X-ray tomography is employed to determine the proportion of each material used in the co-extrusion process. It was found that the modulus of elasticity and tensile strength were significantly improved by 3.5x and 2.3x, respectively, compared to unreinforced thermoplastics. For CP and Qiso laminates, experimental results were compared with predictions from Classical Laminate Theory (CLT). CLT proved suitable for describing stiffness only during the initial stages of deformation (<0.2%).