Fig. shows the simultaneous material injection scenario, where AM and BC particles are added to the extruder together. The porosity of the microstructures obtained from the four sets of simulations reached a minimum point at around 14-17 M 𝛥𝑡, after which it gradually exhibits a nearly periodical up and down fluctuation around a mean value. Note that the difference between the lowest point and the average long-time value is smaller in this case than in the sequential injection scenario. For a given injection scenario, from the mean values measured in the range of 30-70 M 𝛥𝑡, the obtained porosity of the microstructure is an increasing function of the Young modulus. Moreover, the porosity of F4 always has the highest degree of fluctuation. The data in the figure show that porosity decreases at an accelerated rate as the Young modulus of the BC particles decreases. Indeed, the Young modulus of the BC particles in F1, F2 and F3 decreases by about 10 𝑝𝑔 • µ𝑚 -1 • µ𝑠 -2 between each filament, and the final average porosity decreases by about 0.01. Whereas when the Young modulus of the BC particles in F4 is reduced by about 20 𝑝𝑔 • µ𝑚 -1 • µ𝑠 -2 compared to F3, the porosity of F4 is reduced by about 0.04.