The rigidity of the sandwich panel is very important. If it is too soft, the sandwich panel is easily bent and deformed, resulting in collapse and the like. Polyurethane seals the rock wool core layer and makes polyurethane and rock wool a whole. Moreover, the outside of the sandwich panel is wave-pressed, which is much stronger than the conventional composite profiled rockwool. When the rock wool sandwich panel is firmly fixed by the stringer, the rigidity of the layout can be better improved.