Surface Engineering of Thermoplastic Materials and Tooling

Abstract

A prepared mold tool having a thermoplastic surface layer polymer coating on the mold surface of the mold tool or prepared prepreg having a thermoplastic surface layer polymer coating on the surface of the thermoplastic fiber reinforced prepreg are described that enhance first ply laydown of thermoplastic fiber reinforced composite prepregs onto mold tools for prepreg forming or in situ tape placement. Resulting thermoplastic fiber reinforced composite parts from a thermoplastic fiber reinforced thermoplastic composite material having structural reinforcement fibers with one or more high performance polymers, and a thermoplastic surface layer polymer coating which forms a polymer blend with the high performance polymers of the thermoplastic fiber reinforced composite material thereby imparting improved properties, and methods for making and using same, are provided herein.

Description

BACKGROUND OF THE INVENTION[0001]1. Field of the Invention[0002]The subject matter of the present invention relates to fiber reinforced thermoplastic plastic composite materials and particularly to applying a surface layer polymer coating to a composite forming mold tool or to a fiber reinforced thermoplastic prepreg composite material to enhance the first ply laydown of the prepreg onto the composite forming mold tool for prepreg forming or in situ automated laydown tape placement. In situ application of the surface layer polymer coating during or before automated laydown may also provide a beneficial resin rich interlaminar layer between each layer of fiber reinforced thermoplastic composite material. The surface layer polymer coating is preferably thermoplastic particles applied by plasma spraying to the mold tool or prepreg to form a substantially fused layer of thermoplastic particles. More particularly, in certain embodiments the present invention relates to layered fiber rein...

AI Technical Summary

Benefits of technology

The present invention provides a method for improving the adhesion and quality of fiber reinforced thermoplastic composite materials to a mold tool during processing. This is achieved by applying a surface layer polymer coating on the mold tool using plasma spray, which is a compatible chemistry that maintains the dimensions of the composite material and can transfer to the resulting composite part. The resulting composite part has improved interlaminar properties and desirable characteristics, such as fire, corrosion, or wear protection, which come from the surface layer polymer coating. The invention also reduces the initial cost and facility investment to produce large composites. Additionally, the invention improves processing times on ATL machines and manufacturing equipment for producing thermoplastic composite parts with a thickness in the range of 25 to 400 microns.

Problems solved by technology

Thermoset composites suffer from disadvantages including processing problems concerned with removing entrained air or volatiles so that a void-free matrix is produced.

The overall production rate for a structural component is limited by the lengthy cure in the autoclave process step and related operations to prepare the material for that process step.

Thermoplastic resin compositions are more difficult to impregnate into the fiber reinforcing material because of their comparatively higher viscosity than thermosetting resin compositions.

Consequently, it is problematic to make the thermoplastic composite tape adhere to complex mold surfaces during the lay-up process.

Whilst both proposed solutions allow the first layer of thermoplastic composite tape to be successfully applied to complex shaped mold surfaces, they introduce their own problem of how to subsequently remove the formed composite component from the mold when the laying up process is complete, since the component is now effectively bonded to the mold surface.

This method of fabrication is time consuming and cost intensive, and can possibly result in non-uniformity in the lay-up.

Thermoplastic composite materials lack tack, which complicates the use of hand and automated lay-up operations, especially of the first ply against the molding tool surface.

First ply lay-down of thermoplastic materials is complicated by the lack of tack to hold the first layer down to the tool.

Each of these methods has limitations in cost, tool complexity, variation to the dimensions of the part or requires hazardous solvents to practice.

Thermoplastics generally have low surface energies, a high glass transition temperature (“Tg”), making adhesion at room temperature unlikely.

Furthermore, the high performance thermoplastic matrices are in their glass state at room temperature making the molecular diffusion mechanism for tack virtually impossible.

This process step further reduces the total productivity of the composite part operation.

In general, thermoplastic composites have had limited success to date, due to a variety of factors including high processing temperatures (currently around 400° C.

), high pressures, and prolonged molding times needed to produce good quality laminates.

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