Hand lay-up process definition:

Hand lay-up process definition, also known as contact molding process, is a process of manually laying glass fiber fabric and resin on a mold and then solidifying into a FRP product.

Protection molding process classification:

Hand paste molding is divided into wet method and dry method: The wet method is to directly enhance the reinforcing material (cloth, belt, felt) with or without solvent glue, and its impregnation and preforming process At the same time, the specific process of wet hand lay-up is: first apply a layer of release agent on the mold, then evenly apply a layer of resin mixture added with curing agent, and then fiber-reinforced fabric (according to the required shape and size Cut directly on the glue layer, use a scraper, brush or pressure roller to force the resin glue to evenly immerse into the fabric, and eliminate the bubbles. The material to be reinforced is completely pasted by the resin glue, and then cured and demolded. ,Trimming. About 50% of FRP products are currently manufactured using a wet hand lay-up process.

Dry hand lay-up is to pre-form the prepreg according to the layering sequence, separate the impregnation and pre-forming process, obtain the preform blank, and then solidify the molding by molding or vacuum bag-heating can. The specific process of dry hand lay-up is: using prepreg as raw material, first cutting the prepreg (cloth) into blank according to the sample, heating and softening when layering, and then adhering to the mold layer by layer And pay attention to the exclusion of interlayer bubbles, so that the compaction, this method is more often used in autoclave and bag compression molding.

Hand lay-up process features:

The advantage is that the molding is not limited by the size and shape of the product. It is suitable for the production of large-sized, small-volume, complex-shaped products, simple equipment, low investment, quick effect, suitable for the development of township enterprises in China, and technology. Simple, the production technology is easy to master, and it can be produced only after short-term training. It is easy to meet the design needs of the product. It can be arbitrarily added to the reinforcing materials in different parts of the product. The resin content of the product is high and the corrosion resistance is good.

Disadvantages are low production efficiency, slow speed, long production cycle, not suitable for mass production, and the product quality is not easy to control, performance stability is not high, product mechanical properties are low, production environment is poor, odor is large, dust is much during processing, easy to Construction workers caused injuries.

Common defects and solutions in hand lay-up process:

  1. Bubble: When pasting the mold, often due to too much resin, the content of bubbles in the glue is too much, the viscosity of the resin glue is too large, the material of Zengqing is not properly selected, the glass cloth The layer is not pressed tightly, etc., causing a large number of bubbles on the surface of the mold and the cavity, which seriously affects the quality and surface roughness of the mold. At present, the amount of glue is controlled, the resin glue is vacuum defoamed, and an appropriate amount of diluent is added. (such as acetone), choose to use a glass cloth that is easy to saturate the resin, etc. to reduce the generation of bubbles.
  2. Flowing glue: When the mold is manually pasted, the phenomenon of glue flowing often occurs. The main reasons for the flow of glue are: a. The viscosity of the resin is too low, B; the ingredients are not uniform, and the amount of curing agent is less. The filler increases the viscosity of the resin (such as silica), and appropriately adjusts the amount of the curing agent to avoid the occurrence of flow.
  3. Layering: Due to the insufficient amount of resin and the lack of tightness of the glass cloth layer, the heating temperature of the premature heating product is too high, etc., which will cause the mold to stratify. Therefore, in the paste, it is necessary to control enough glue, try to The laminate is laminated, and the resin is not heated as much as possible before the gel, and the heating temperature is appropriately controlled.
  4. Cracks: When making and using molds, we often see cracks on the surface of the mold. The main reason for this phenomenon is that the gel coat layer is too thick and affected by uneven hair removal. The thickness of the mold gel coat should be strictly controlled. When demoulding, the mold should be punched with a hard object, preferably with compressed air.

In the future

I must rely on independent innovation in the composite materials industry, take enterprises as the main body, highlight capacity cultivation, attach importance to original innovation, vigorously develop standardized, institutionalized, intensive absorption into the new production mode of composite materials, and want to develop in depth and attach importance to protection knowledge. Property rights, strengthen industry self-discipline, reduce low-level vicious competition at low prices, and focus on developing products and markets in the fields of environmental protection, renewable energy, construction, chemical anti-corrosion, transportation (including land vehicles, ships, aviation, aerospace), etc. Transforming from a large composite country to a strong composite country.

By Kalumi