Effect of fiber steering and drilling in notched continuous fiber 3D-printed composites

Purpose: Continuous fiber thermoplastics are recyclable and have excellent specific strength and stiffness, making them desirable materials for use in structural components. Recent advancements in continuous fiber additive manufacturing processes allow designers to make notches or perforations during printing, eliminating the need for labor-intensive and long drilling processes, which cause delaminations and premature failure. The purpose of this study is to evaluate the potential of continuous fiber 3D printing in creating notches for structural composites. Design/methodology/approach: This study evaluates the notching process in nylon-based continuous-glass fiber thermoplastic composites through mechanical drilling and three-dimensional (3D) printing. Three different sample configurations were tested for tensile and fracture characteristics: Un-notched; with notches drilled mechanically; and with notches printed using a 3D printer, with the fibers routed around the notch. Further, finite element models were used to understand the stress concentration around the notches. Findings: The tensile strength of notched samples was lower than that of unnotched samples in both 3D-printed and mechanically drilled cases. The presence of substantial delamination in mechanically drilled samples led to a 15% decrease in strength compared to 3D-printed samples. The increase in notch size resulted in a decrease in strength, as anticipated. Practical implications: The techniques developed in this study may be easily applied to comparable situations involving several types of continuous fiber thermoplastic composites. Originality/value: Both experimental and computational modeling results indicate that delamination because of the drilling process is the prime factor responsible for the significant decrease in residual strength. Furthermore, it also showed that the steering of the fiber around the notch had a minimal impact, and augmenting the stiffness in proximity to the notch can alleviate stress concentration.