Lay-up manufacturing is the most common composite production method used.
Hand Lay-up Technique
Composite hand lay-up is the uncomplicated process of composite manufacturing. The infrastructural requirement for this process is also minimum. The processing steps are manageable. Firstly, a release agent is applied to the mould surface to avoid the sticking of the composite part. Reinforcement in the form of woven mats is cut as per the mould size and arranged at the surface of the mould. The thermosetting resin is mixed thoroughly in suitable proportion with a prescribed hardner (curing agent) and applied onto the surface of the mat already placed in the mould. The resin is evenly spread with the help of a brush. The second layer of mat is positioned on the polymer surface, and a roller is moved with mild pressure on the mat-polymer layer to remove any air trapped as well as the excess polymer present. The process is repeated for each layer until the required amount of layers are stacked.
After curing either at room temperature or some specific temperature, the mould will be opened, and the developed composite part is taken out and further processed.
The production rate is less and the high volume fraction of reinforcement is difficult to achieve in the processed composites. Composite hand lay-up method finds application in many areas like aircraft components, automotive parts and boat hulls.
Resin Infusion Process is a technique that uses vacuum pressure to drive resin into a laminate. Materials are laid dry into the, and the vacuum is applied before the resin. Once a complete vacuum is achieved, the resin is pulled into the laminate via carefully placed tubing. An assortment of supplies and materials aids this process. In a typical hand lay-up, reinforcements are laid into a mould and manually wet out using brushes, rollers, or through other means. An improvement on that method is to use a vacuum bag to suck excess resin out of the laminate. Vacuum bagging dramatically improves the fibre-to-resin ratio and results in a stronger and lighter product. Resin infusion requires experience and uses many of the same principles. Vacuum/Resin infusion builds upon these principles, providing further improvements to the lamination process.
The Hand Prepreg lay-up is the most widely used method; therefore often used for aerospace composites parts and structures or within motorsport. For these components quality and repeatability is mandatory. When using a pre-impregnated fabric the material is already provided with the correct amount of resin to ensure the desired mechanical properties.
Specific Tensile Strength of various materials
- Glass fiber
- Carbon fiber
- Aramid fiber
mat, stitched into a fabric form, mat of randomly oriented fibers
- Epoxy resin
- Vinyl Ester