Pre-consolidation of thermoplastic fiber preforms and method of making the same
A process is provided for forming a pre-consolidated fiber preform for use in a molding process. The process includes layering a plurality of preform sheets on a pre-consolidation mold. Heating the plurality of preform sheets to a first temperature. Applying a first pressure to the plurality of preform sheets using the pre-consolidated mold. Maintaining the first temperature and the first pressure and heating for a first duration of time. A second pressure and a second temperature are then applied to the plurality of preform sheets for a second duration of time.
1. A process of forming a pre-consolidated fiber preform for use in a molding process, the process comprising:
layering a plurality of preform sheets on a pre-consolidation mold, each of the plurality of preform sheets formed of at least one comingled continuous fiber bundle arranged in a curvilinear pattern and held in place on a substrate with stitching, the comingled continuous fiber bundle containing both reinforcing fibers and matrix fibers;
heating the plurality of preform sheets to a first temperature;
applying a first pressure to the plurality of preform sheets using the pre-consolidated mold;
maintaining the first temperature and the first pressure and heating for a first duration of time; and
applying a second pressure and a second temperature to the plurality of preform sheets for a second duration of time.
2. The process of claim 1 further comprising forming the plurality of preform sheets.
3. The process of claim 1 wherein the plurality of preform sheets comprise reinforcing fibers and matrix fibers.
4. The process of claim 1 wherein the second temperature is lower than the first temperature.
5. The process of claim 1 wherein the first temperature is a temperature above a melting point of a thermoplastic ingredient in the plurality of preform sheets.
6. The process of claim 1 wherein the second temperature is a temperature below a melting point of a thermoplastic ingredient in the plurality of preform sheets.
7. The process of claim 1 wherein induction heaters provide heat to heat the plurality of preform sheets to the first temperature and the second temperature.
8. The process of claim 1 wherein the first pressure is greater than the second pressure.
9. The process of claim 1 wherein the first pressure is 300 psi.
10. The process of claim 1 wherein the first duration is 30 seconds to 25 minutes.
11. The process of claim 1 wherein the first duration is 2 minutes.
12. The process of claim 1 wherein the second duration is 30 seconds to 25 minutes.
13. The process of claim 1 wherein the second duration is 2 minutes.
14. The process of claim 1 wherein the pre-consolidation mold has a three-dimensional shape.
15. The process of claim 1 wherein the pre-consolidated fiber preform retains a shape of the pre-consolidation mold.
16. The process of claim 1 further comprising applying an epoxy powder between the layers of the plurality of preform sheets.
17. The process of claim 1 further comprising applying a plurality of chopped fibers between the layers of the plurality of preform sheets.
18. The process of claim 1 wherein the molding process is any of liquid composite molding (LCM), resin transfer molding (RTM), over molding, or compression molding.
19. The process of claim 1 further comprising preheating the pre-consolidated fiber preform and placing the pre-consolidated fiber preform into a mold for forming a molded part.