“…To obtain the material η 0 , the Carreau–Yasuda model was used to analyze the complex viscosity of PCL and HA/PCL composites as a function of frequency, as it not only describes the Newtonian behavior of the fluid at low shear rates but also captures the shear thinning process at high shear rates. The complex viscosity η of polymers is generally described using the Carreau–Yasuda model [ 70 ]: where η ∞ is the infinite shear viscosity, η 0 is the zero-shear viscosity, λ is the relaxation time, n is the power law index, and a is the width of the transition region between Newtonian and power law behavior. The zero-shear viscosities of virgin PCL, PCL, 5HA/PCL, 10HA/PCL, and 20HA/PCL were determined to be 3304.3 Pa·s, 5522.7 Pa·s, 7817.6 Pa·s, 9092.6 Pa·s, and 8177 Pa·s, respectively (the fitting parameters are presented in Table S2 ).…”