Process evaluation, tensile properties, mathematical models, and fracture behavior of 3D printed continuous fiber reinforced thermoplastic composites

Abstract

Continuous fiber reinforced thermoplastic composites with advantages of high strength, long life, corrosion resistance, and green recyclability have been widely used in aerospace, transportation and high-precision processing equipment, etc. 3D printing is an advanced additive manufacturing technology that enables the rapid manufacture of complex structures and high-performance composites. The aim of this study is to evaluate the precision and stability of 3D printed continuous fiber reinforced thermoplastic composite structures and construct suitable mathematical models to predict tensile properties. Samples evaluated in this study were produced by varying the volume fraction and distribution mode (average and central mode) of fibers within the printed structures. The measured data proved the continuous fiber reduced the printing precision on width and thickness and the printing stability on thickness, while it improved the width stability in the XY horizontal plane. The printing precision and stability of samples with an average mode were slightly better than those of samples with a central mode. The tensile results of 3D printed continuous fiber reinforced thermoplastic composites demonstrated that an increasing volume of fiber reinforcement resulted in the increasing stiffness and ultimate strength of tested samples. The average elastic modulus and ultimate tensile strength of samples with the average mode were higher than those of samples with the central mode, while the average strain at break was quite the opposite. Mathematical models of elastic modulus were established to achieve the relative errors 0.06% and 2.14% for checked samples, while relative errors of the mixing rule were up to 76.15% and 81.71%, respectively. Some typical defects affecting the surface quality and the fracture behavior of 3D printed samples were researched by the analysis of micromorphology.