The hand lay-up process is the oldest to produces very large parts from FRP laminates. There are few application steps for the hand-lay-up process which are explained here.
First, we need to state that the hand-lay up process is the open-mold process that molds are not closed as halves as in conventional molds. If the mold is ready to use, the mold release agent is sprayed and applied to the mold surface to facilitate the separation of the produced part from the mold.
As a first layer, pigmented resin gel is sprayed on the surface. Pigments will give the surface color of the part. To apply the first layer of fiber or prepreg, the gel must be partially cured.
After the gel is partially cured, successive layers of resin and composite fibers are applied. Rolling of these layers must be established carefully to prevent any air bubbles entrapped between layers and complete the impregnation completely.
After this step, mold is left to be fully cured. After the resin layers are completely cured, the part is removed from the mold.
Actually, a wide range of materials can be used to mold production for hand lay-up processes. Metals, plasters, glass-fibers can be used in mold production. Selection of material for hand lay-up mold production depends on the process parameters such as; surface characteristics, production volume.
For high-production rates, metal molds are proper. Because metal’s durability and surface wear resistance are better than others. Also, metal molds are proper for the dissipation of heat produced at the curing period of resins.
For prototype production, plaster molds are used because of the low cost of machining. For medium production rates, generally, fiber-glass molds are used.
Generally, large and thin products are produced from hand lay-up processes such as boat hulls and swimming pools. As you understand from its name, laying of laminations made by people has the profession about it. So, handicraft is very important in hand lay-up processes.
Hand lay-up processes can be also used for amateur purposes. This article can be a very good starting point to learn hand lay-up processes for amateurs also.
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