Molten Chopped Prepreg Extrusion for Low-Mass Compression Molds

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Solution Overview

Problem

Existing methods for fabricating composite parts using chopped prepreg fiber result in inefficient use of molding dies due to the bulk factor of unconsolidated fiber stacks, leading to increased thermal mass and longer cycle times.

Innovation Solution

Applying molten chopped prepreg fiber directly to compression molding dies, allowing controlled fiber orientation and reducing die size by eliminating the need for large receptacles, achieved through a two-step process of extrusion and pressing with complementary male and female dies.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Ease of manufacture

If unconsolidated chopped prepreg fiber is stacked into a die for molding, then the fiber pieces can be easily loaded, but the air gaps between pieces increase the volume occupied by the stack

Engineering Contradiction:

Improveease of loading fiberVSAvoiddie volume

Core Design Contradiction:

Ease of manufactureVSVolume of stationary object

Solution Approach 1:

The patent changes the physical state of the chopped prepreg fiber from solid/unconsolidated to molten by heating above the melting temperature of the thermoplastic matrix. This parameter change eliminates air gaps between fiber pieces, allowing the fiber to be densely packed into the die cavity without requiring excessive die volume to accommodate the bulk of unconsolidated fiber.

Inventive Principle:

Principle #35Parameter changes

2Quantity of substance

If larger die volume is used to accommodate unconsolidated fiber stack, then all fiber pieces can be contained, but the thermal mass of the die increases

Engineering Contradiction:

Improvefiber contentVSAvoiddie mass

Core Design Contradiction:

Quantity of substanceVSWeight of stationary object

Solution Approach 1:

By changing the fiber to molten state, the patent achieves dense packing that maintains adequate fiber quantity while significantly reducing the die volume required. This volume reduction directly decreases the die mass and thermal mass, addressing the contradiction between containing sufficient fiber and minimizing die weight.

Inventive Principle:

Principle #35Parameter changes

3Quantity of substance

If larger die volume is used, then sufficient fiber can be accommodated, but the heating requirements and cycle times increase

Engineering Contradiction:

Improvefiber contentVSAvoidheating energy

Core Design Contradiction:

Quantity of substanceVSUse of energy by stationary object

Solution Approach 1:

The patent applies heat to melt the thermoplastic matrix in the chopped prepreg fiber, transforming it from a bulk-filled solid state to a flowable molten state. This parameter change enables the fiber to conform to the die cavity shape with minimal volume, reducing the die size and consequently the energy required to heat the die, while still accommodating sufficient fiber content.

Inventive Principle:

Principle #35Parameter changes

4Quantity of substance

If larger die volume is used, then all fiber pieces can be contained, but the cycle time increases

Engineering Contradiction:

Improvefiber contentVSAvoidcycle time

Core Design Contradiction:

Quantity of substanceVSLoss of time

Solution Approach 1:

By heating the chopped prepreg fiber above the melting temperature of the thermoplastic, the patent creates a molten state that flows to fill the die cavity efficiently. This eliminates the need for large die volumes to accommodate unconsolidated fiber, thereby reducing the thermal mass and enabling faster heating and cooling cycles, thus decreasing the overall manufacturing cycle time.

Inventive Principle:

Principle #35Parameter changes

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

Reduces die size and thermal mass, resulting in faster cycle times and reduced energy requirements while ensuring uniform composite part formation.

Implementation Method 1

heating an extruder above a melting point of a thermoplastic within chopped prepreg fiber, in order to melt chopped prepreg fiber disposed within the extruder

Methodology Applied

Scientific EffectHeating: Heating

Implementation Method 2

pressing the male die into the female die, causing the molten chopped prepreg fiber to fully enter receptacle

Methodology Applied

Scientific EffectCompression: Compression

Implementation Method 3

cooling the chopped prepreg fiber in the receptacle of the female die to form the composite part

Methodology Applied

Scientific EffectCooling: Cooling

Data Source

PatentEP3715082B1Molten extrusion loading for compression molds using chopped prepreg fiber

Publication Date: 2026.03.04 THE BOEING CO

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AI summary

Systems (300, 900) and methods (200) are provided for fabricating composite parts. One embodiment is a method (200) that includes heating (202) a female die (120, 920) having a receptacle (124, 924) and a complementary male die (110, 910), heating (206) an extruder (320, 800, 950) above a melting point of a thermoplastic within chopped prepreg fiber (652, 860, 956), in order to melt the chopped prepreg fiber (652, 860, 956) disposed within the extruder (320, 800, 950), extruding (208) the chopped prepreg fiber (652, 860, 956) from the extruder (320, 800, 950) into the receptacle (124, 924) of the female die (120, 920) while the chopped prepreg fiber (652, 860, 956) remains molten, pressing (210) the male die (110, 910) into the female die (120, 920), causing the molten chopped prepreg fiber (652, 860, 956) to fully enter the receptacle (124, 924), and cooling (212) the chopped prepreg fiber (652, 860, 956) in the receptacle (124, 924) of the female die (120, 920) to form the composite part.