A PreRreg consists of a reinforcement material pre impregnated with a resin matrix in controlled quantities. The resin is partially cured to a B-stage, and in this form is supplied to the fabricator, who lays up the finished part and completes the cure with heat and pressure. The required heat and pressure will vary with the resin system and the intended application.
|Prepreg Application Process|
|Basalt Fiber Tech Prepreg Application Process©2015 - Designed by Lucas Sant'Anna|
- Basfiber® Fabrics are positioned according to the PrePreg specification. Different thickness and weaves can be used to achieve the desired strength and malleability.
- Reinforcing Material can be added to enhance the desired proprieties of the final product. The reinforcing material can be different thickness of Basfiber® Fabrics, Carbon or Aramid.
- Alignment Machine can be used to put the Basfiber® Fabrics and the reinforcement material in the correct position to receive the resin. The layers are positioned according to the strength and flexibility needed to the final material.
- The Resin Impregnation Chamber distributes the resin equally to the material, assuring that the Basfiber® Fabrics will impregnate the resin within the reinforcing material while it heats to the temperature needed to the next pressurizing phase.
- The Pressurizing machine applies pressure to the fabric while remove the excess of resign at the same time that pulls the fabrics through the impregnation machine. This machine also keeps the temperature of the PrePreg avoiding the curing.
- Silicon Layer is attached to the resin impregnated fabric to enable the PrePreg to be rolled without the risk of resin transfer from the fabric and also to facilitate the application of the PrePreg on the final material/product.
- The Rolling Machine rolls the PrePreg fabric in the customer customized or in ours standard lengths and then get cut.
- Final Product is a roll of PrePreg fabric which can be applied to any surface or mould. The PrePreg roll must be stored in a refrigerated place to avoid it for curing.
A PrePreg is available in :
- UNIDIRECTIONAL (UD) form (one direction of reinforcement)
- FABRIC form (several directions of reinforcement)
Advantages of PrePreg vs Lay Up
- Low void content.
- Control of fibre volume fraction.
- Control of laminate thickness.
- Lower labour cost.
- Better quality and conformity.
- Clean process.
- Vacuum bag moulding.
- Autoclave moulding.
- Press moulding.
- Pressure bag moulding.
- Thermal expansion moulding.
- Tube rolling.
The cure cycle is the process whereby the resin within the PrePreg changes from a liquid to a solid through the application of heat. There are a number of stages in this cycle.
Cure Temperature / Time
For each PrePreg resin system there is a range of options for cure temperature / duration. There is also a minimum cure temperature. For a given cure temperature there will be a corresponding cure time. The oven/autoclave, laminate, and tooling should all reach and maintain the given cure temperature throughout the specified cure cycle. Thermocouples are used to monitor the temperature of the laminate and tooling.
Heat Up Rate
The heat up rate is a measure of how quickly the laminate / tool is brought up to the cure temperature. This is governed by numerous factors;
- Matrix Viscosity
- Matrix Reaction Rate
- Thickness of Laminate
- Tool mass
- Tool conductivity
For highly reactive matrices and thick laminates the heat up rate will be low, and may incorporate an intermediate temperature soak, in order to avoid exothermic reactions.
The cooling rate is controlled in order to avoid sudden temperature drops that may induce thermal stresses in the component.
Vacuum / Pressure
At specific stages in the cure cycle, vacuum and pressure are applied and removed.