Patent ID: 7473385

Claim:
A method for making a windmill blade of composite materials that include a fiber reinforced matrix material, the improvement comprising that the blade is made in one piece in a closed mold and comprising steps that provide: a removable mold core with a flexible external core part wrapped around an internal, firm or workable core part and surrounded by a flexible, air-tight membrane, and outer mold parts arranged to close around the mold core for formation of a mold cavity there between, that composite material is laid on an outer mold part and/or the mold core, that at least one flow pipe is placed in the mold cavity at the side edge for injecting matrix material, that the outer mold parts are closed around the mold core and around the composite material placed in the mold cavity, that the composite material is set, that the outer mold parts are removed, and that the mold core is taken out of the shape permanent blade before or after removing the outer mold parts, wherein some of the required matrix material is used in connection with the reinforcing fibers when laying the composite material and where additional matrix material is injected via the flow pipe after closing the mold, wherein the composite material is laid around a sandwich core material for forming the blade as a sandwich structure by providing a first inner layer of fiber material on an inner side of the sandwich core material and by providing a second, outer layer of fiber material on an outer side of the sandwich core material, wherein the first layer covers at least part of a surface of the second layer or wherein the second layer covers at least part of the surface of the first layer, where the sandwich core material is used for evacuation and flow at vacuum formation of the blade as the mold cavity is subjected to vacuum whereby air is evacuated simultaneously with composite materials being pressed against the inner side of the outer mold parts due to expansion of the flexible membrane of the mold core, and where the matrix material is injected following formation of the mold cavity by vacuum.