the designed composites with 20 vol.% fiber fraction can be completely realized using the selected materials and the prepared preforms cannot have pores. As regards the slurry properties, they are directly concerning with the relative ratio of the three parts (PMMA, acetone and powders) composing the slurry.The slurry viscosity is mainly determined by the acetone, while the preform strength completely relies on the content of PMMA binder. A slurry with high viscosity is difficult to completely penetrate into the space between fibers, and thus the prepared preforms have macro-pores, as shown in Fig. 1a; whereas, a slurry with low viscosity is difficult to be coated on the fibers to reach a required thickness, and the powders in the slurry tend to precipitate because of the long solidifying time, as illustrated in Fig. 1b.