Through-Thickness Permeable Prepregs for Void Reduction
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Solution Overview
Problem
Current composite prepreg manufacturing methods, especially those using autoclaves, face limitations in air removal during consolidation and cure, leading to internal porosity and surface defects, and alternative out-of-autoclave methods struggle with resin flow and permeability issues, particularly in large or complex parts.
Innovation Solution
The development of through-thickness air or gas permeable prepreg assemblies featuring a fiber bed with discrete resin regions on its surface, combined with an air permeable resin barrier material, allows for efficient air removal and resin saturation, reducing internal porosity and surface defects by preventing resin bleed during processing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-generated harmful factors
If conventional OoA prepregs with in-plane breathing pathways are used, then air removal is facilitated in the plane of the fiber bed, but out-of-plane air evacuation is limited due to resin covering the surfaces
Solution Approach 1:
The patent transitions from in-plane air removal pathways to out-of-plane breathing pathways by applying porous PTFE film to the surfaces of the fiber bed. This dimensional change allows air to escape perpendicular to the fiber bed plane, effectively solving the limitation of resin-covered surfaces blocking traditional in-plane evacuation routes.
Solution Approach 2:
The porous PTFE film acts as an intermediary layer between the resin and the external environment. It allows air and volatiles to pass through while preventing resin from escaping, thereby mediating the conflicting requirements of maintaining resin containment while enabling air removal.
2Object-generated harmful factors
If Z-preg with wide resin strips is used, then through-thickness air permeability is improved, but resin-flow issues occur including excessive resin bleed and premature occlusion of breathing pathways
Solution Approach 1:
The patent employs porous PTFE film as a breathing pathway provider instead of relying on resin strip spacing. The porous structure inherently allows air permeability while maintaining precise control over resin flow, eliminating the resin bleed and pathway occlusion issues associated with Z-preg's wide resin strips.
Solution Approach 2:
The PTFE film serves as a temporary, consumable component that fulfills its air removal function during processing and is then discarded or removed. This disposable approach avoids the permanent structural modifications and resin flow control issues of Z-preg designs.
3Reliability
If autoclave curing is used, then consolidation and cure are achieved, but production rates are limited and costs increase
Solution Approach 1:
The patent extracts the air removal function from the autoclave environment and integrates it directly into the prepreg structure itself through the porous PTFE film. This extraction eliminates the need for autoclave equipment, thereby increasing production rates and reducing costs while maintaining consolidation quality.
Solution Approach 2:
The prepreg structure becomes self-sufficient for air removal during curing through its integrated porous PTFE film breathing pathways. This self-service capability eliminates dependence on expensive autoclave equipment, enabling simpler, faster, and more cost-effective processing.
4Object-generated harmful factors
If in-plane breathing pathways are used, then air removal is effective for small parts, but large parts with long breathe-out distances and complex geometries suffer from trapped air
Solution Approach 1:
The patent provides air escape routes in the out-of-plane direction through porous PTFE film application on surfaces, enabling efficient air removal from large and complex parts regardless of their in-plane dimensions. This dimensional approach eliminates the breath-out distance limitation of in-plane pathways.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This approach significantly reduces internal porosity and surface defects, enabling the production of high-quality composite structures with near-zero internal voids and flawless external surfaces, while also eliminating the need for autoclaves, thus improving production efficiency and reducing costs.
Implementation Method 1
an air permeable resin barrier material, such as a porous polytetrafluoroethylene (PTFE) film, that facilitates the passage of air and/or volatiles from the prepreg but prevents the passage of resin from the prepreg
Implementation Method 2
discrete resin regions on the surface of the fiber bed that facilitates air removal in a through-thickness direction from the prepreg during a processing, such as a curing process
Data Source
AI summary
Through-thickness permeable prepregs comprise a fiber bed and a plurality of discrete resin regions on a surface of the fiber bed separated by exposed fiber bed surface regions. Prepreg assemblies for processing such prepregs comprise an air permeable resin barrier material disposed over a surface of the prepreg opposite a forming tool. The air permeable resin barrier material is permeable to air or gas passing from the prepreg and is impermeable to resin passing from the prepreg. During processing, the prepreg assembly is subjected to a vacuum and elevated temperature to cure the resin and form a composite part. During processing, the air permeable resin barrier material prevents unwanted resin bleed from the prepreg, causing resin pressure in the prepreg to be maintained that reduces or eliminates unwanted formation or growth of internal voids to provide a composite part having a reduced degree of internal voids and pores.