Prepreg Void Reduction via Accelerated Cure Kinetics
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Solution Overview
Problem
Fiber-reinforced composite materials face challenges in void formation due to trapped volatiles during processing, particularly in large structures and complex geometries, leading to increased processing times and reduced mechanical properties when using vacuum bag or autoclave methods, as current techniques struggle to ensure full consolidation and efficient volatile removal.
Innovation Solution
A prepreg system comprising a thermosetting epoxy resin with carbon fibers, incorporating a phenol or sulfonic ester accelerator to control the cure rate, allowing for full consolidation at an intermediate temperature before reaching a 20% cure point, thereby reducing void growth and processing time, while maintaining high Tg and impact resistance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If reduced temperature cure is used to reduce disassociation of volatiles and decrease void growth, then void content is reduced, but processing time increases due to slower cure time
Solution Approach 1:
The patent modifies the cure rate parameters by incorporating accelerators (phenol or sulfonic ester) into the epoxy resin system. This chemical parameter change enables the resin to cure faster at reduced temperatures, simultaneously reducing void content from volatile disassociation and decreasing processing time, thus resolving the contradiction between manufacturing precision and loss of time.
2Productivity
If faster cure rate is used to reduce processing time, then productivity is improved, but consolidation time is insufficient leading to increased void content
Solution Approach 1:
The patent adjusts the cure rate parameter through the addition of accelerators to the epoxy resin. This enables the system to achieve optimal consolidation quality by maintaining sufficient consolidation time while reducing overall processing time through enhanced cure kinetics, thus resolving the contradiction between productivity and manufacturing precision.
3Manufacturing precision
If autoclave or vacuum bag processing is used to apply pressure for consolidation, then consolidation quality is improved, but trapped volatiles increase void content
Solution Approach 1:
The patent changes the chemical parameters of the epoxy resin by incorporating accelerators, which reduces the cure temperature and extends the working time window. This allows for more effective volatile removal during consolidation under vacuum bag or autoclave processing, reducing void content while maintaining consolidation quality.
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
The controlled cure rate enables efficient void reduction and faster processing times, resulting in high-quality fiber-reinforced composites with reduced porosity and enhanced mechanical properties, suitable for aerospace and other demanding applications.
Implementation Method 1
heat may be applied to cause the matrix resin to flow, enabling consolidation of the prepreg layers. The applied heat may additionally cure or polymerize the matrix components.
Implementation Method 2
heat may be applied to cause the matrix resin to flow, enabling consolidation of the prepreg layers
Implementation Method 3
Gases may be trapped from insufficient evacuation of the air before full consolidation by evacuation of the air path
Data Source
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AI summary
Embodiments herein relate to a prepreg comprising a thermosetting resin, and reinforcing fibers in the thermosetting resin, wherein when the prepreg is cured in vacuum bag only conditions, and a method of making the same. The method also applies for autoclave processing. Embodiments also relate to a cured fiber reinforced composite material made by thermally curing the prepreg.