Methods for combining components of varying stages of cure

Abstract

The present invention provides a method of fabricating a composite structure from components of varying stages of cure while reducing the steps associated with the fabrication process of infusing, curing, and bonding composite materials to form a hybrid unitized structure. The method provides a pre-cured stiffener and a pi-preform having a clevis and a base portion. The pre-cured stiffener may be inserted into the clevis of the pi-preform to form a composite structure assembly. The composite structure assembly may be infused with a resin system at the time of cure and bonded to a second composite structure to form a hybrid unitized structure.

Description

TECHNICAL FIELD[0001]The present invention relates generally to composite materials. More particularly, the invention relates to methods for combining components of varying stages of cure and for creating unitized hybrid composite structures.BACKGROUND INFORMATION[0002]Over recent years, composite materials have become an increasingly desirable material for aircraft structures. Composite materials typically comprise strands of fibers (e.g., glass- and / or carbon-fiber) mixed with a resin. For example, many commercially produced composites use a polymer matrix material as the resin. In fact, there are many different polymers available, depending upon the starting raw ingredients. The more common polymer may include, for example, polyester, vinyl ester, epoxy, phenolic, polyimide, polyamide, polypropylene, and PEEK. During fabrication, fibers may be often wound, or woven, into a sheet of material and then impregnated (e.g., infused) with a resin. Once the fibers have been impregnated w...

AI Technical Summary

Benefits of technology

The present patent is about methods for creating composite structures by combining components of varying stages of cure and materials. The methods involve infusing a composite structure with resin to yield a cured assembly. The resulting composite structure has structural support and is strong and durable. The methods also allow for the creation of a hybrid unitized structure by combining different components in a specific way. The stiffener component provides structural support and the dry fabric component is secured to the stiffener component. The method involves wrapping resin film around the stiffener component and inserting it into the dry fabric component to form a composite structure assembly. The assembly is then heated to a specific temperature for a specific period of time to cure it. The resulting composite structure has improved strength and durability.

Problems solved by technology

While many parts manufactured using composite materials could also be made from metal, a metallic part of the same strength and stiffness would be significantly heavier.

Initially, pre-preg is flexible and sticky, but becomes hard and stiff once it has been heated (i.e., during the curing process).

However, as recognized by U.S. Pat. No. 7,681,835 to Simpson et al., a drawback to certain composite materials is the actual assembly, or joining, of the composite materials.

For example, placing holes in composite materials for attachment of fasteners severs the strands of fibers within the material and creates weak points within the material.

While forming holes in the composite material by displacing the strands of the uncured fibers prevents severing of the fibers, this process is time-consuming and often impractical.

However, the distribution of the epoxy and the placement of the parts together can require expensive machines and numerous jigs (e.g., tooling).

Moreover, such structures routinely involve multiple sets of tools, are very labor intensive, require several cure cycles and can require B-staged material with set expiration dates.

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