Fiber-reinforced investment casting composite shell

The utility model relates to a fiber-reinforced investment casting composite shell. In order to solve the problems of lower wet strength and poor air permeability of the conventional casting shell, the composite shell adopts the structure that a silica sol coating surface layer, a silica sol coating transition layer, a silica sol coating back layer and a silica sol coating slurry seal layer are arranged from the inside to the outside, wherein the silica sol coating surface layer is filled with zircon powder; the silica sol coating transition layer is filled with mullite powder; the silica sol coating back layer is filled with fiber-reinforced mullite powder; the silica sol coating slurry seal layer is filled with fiber-reinforced mullite powder; stucco inserted layers are arranged between the silica sol coating surface layer and the silica sol coating transition layer, between the silica sol coating transition layer and the silica sol coating back layer, and between the silica sol coating back layer and the s