Effect of Annealing on High Temperature Tensile Performance of 3D Printed Polyamide Carbon Fiber: A Comparative Study

Fused filament fabrication of thermoplastic composites, despite its recyclability, increased strength, and efficiency, faces structural limitations under elevated temperatures. The literature on heat treatments for improving the thermal resilience of accessible 3D printed composites is limited. Therefore, this study comprehensively presents the efficacy of annealing on carbon fiber reinforced polyamide (PAHT-CF). The methodology includes uniaxial tensile testing of 200 samples across a wide temperature range (25–150 °C) and five different infill orientations, annealed as per the Technical Data Sheet (80 °C, 12 h). Scanning electron microscopy (SEM) of the fracture surfaces revealed the microstructural changes responsible for the improved properties after annealing. At 25 °C, annealing led to a 50% strength increase (63.88 MPa) and a 70% lower strain (2.65%). At 150 °C, the material maintained a 17.5% strength advantage (23.62 MPa) and a 17.5% reduction in strain (12.67%). The 0°, 90°, and 0/90° orientations exhibited the highest improvements, while the remainder displayed lower strengths and higher deformation beyond the glass transition temperature (70 °C). Overall, annealed PAHT-CF demonstrates high-temperature resilience, comparable to previously analyzed materials like carbon fiber reinforced polyether–ether–ketone (PEEK-CF). This makes it a potentially accessible alternative for the aerospace and automotive sectors. However, practical applications must consider the trade-off between its enhanced mechanical properties and the increased lead time from annealing.