Inflatable Radius Filler for Composite Fillet Curing

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Solution Overview

Problem

Conventional manufacturing techniques for composite structures with T-shaped or I-shaped cross sections, which typically use radius fillers in fillets, often result in structural issues such as ply distortion and voids, particularly in aircraft and watercraft construction.

Innovation Solution

A method involving the use of an inflatable radius filler positioned in the fillet, which is then vented and subjected to a vacuum chamber for curing, eliminating the need for traditional radius fillers and allowing for a uniform cure pressure that reduces ply distortion and voids, while maintaining an air radius in the fillet.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Ease of manufacture

If traditional radius fillers are used in fillets, then the fillet region can be filled and cured, but structural issues such as ply distortion and voids occur

Engineering Contradiction:

Improveease of manufactureVSAvoidstructural integrity

Core Design Contradiction:

Ease of manufactureVSReliability

Solution Approach 1:

The patent removes the traditional radius filler material from the fillet region and replaces it with an inflatable radius filler that creates a void space. This extraction of the harmful filler material eliminates the source of ply distortion and voids while maintaining the structural integrity of the composite part.

Inventive Principle:

Principle #2Taking out (Extraction)

Solution Approach 2:

The patent changes the physical state and properties of the radius filler from a solid traditional filler to an inflatable structure that can be deflated and removed. This parameter change allows the filler to serve its temporary support function during manufacturing while eliminating structural issues in the final product.

Inventive Principle:

Principle #35Parameter changes

2Manufacturing precision

If traditional radius fillers are used in fillets, then the fillet can be formed, but the composite part contains voids and structural defects

Engineering Contradiction:

Improvefillet formation precisionVSAvoidstructural quality

Core Design Contradiction:

Manufacturing precisionVSReliability

Solution Approach 1:

The patent extracts the harmful traditional radius filler material and replaces it with an inflatable radius filler system that can be completely removed after curing. This extraction eliminates the source of voids and structural defects while maintaining precise fillet formation during the manufacturing process.

Inventive Principle:

Principle #2Taking out (Extraction)

Solution Approach 2:

The inflatable radius filler serves as a temporary intermediary structure during manufacturing that maintains the correct fillet geometry without introducing structural defects. It mediates between the need for precise fillet formation and the requirement to avoid voids and structural quality issues in the final product.

Inventive Principle:

Principle #24Intermediary (Mediator)

3Reliability

If radius fillers are removed completely, then structural issues are eliminated, but the fillet region lacks support during curing

Engineering Contradiction:

Improvestructural integrityVSAvoidmanufacturing processability

Core Design Contradiction:

ReliabilityVSEase of manufacture

Solution Approach 1:

The patent applies preliminary action by positioning the inflatable radius filler in the fillet region before curing occurs. This preliminary placement provides the necessary support and geometry maintenance during the curing process, while the filler is designed to be removable afterward to eliminate structural issues.

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The patent introduces dynamics by using an inflatable radius filler that can be inflated to provide support during manufacturing and then deflated and removed after curing. This dynamic approach allows the filler to serve its support function temporarily while being eliminated from the final structure to maintain structural integrity.

Inventive Principle:

Principle #15Dynamics

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 enhances manufacturing efficiency by eliminating structural issues associated with radius fillers, enabling the production of lightweight and strong composite components without the need for traditional fillers, thus improving the assembly and serviceability of aircraft and other composite structures.

Implementation Method 1

drawing a vacuum in the vacuum chamber

Methodology Applied

Scientific EffectVacuum: Vacuum

Implementation Method 2

venting the inflatable radius filler to an environment external to vacuum chamber

Methodology Applied

Scientific EffectVenting:

Data Source

PatentEP2803474B1Composite structure and method

Publication Date: 2017.10.04 THE BOEING CO

Figure 1~2
Figure 3A~3C
Figure 3D~3E

AI summary

Method to form a composite part comprises joining a first structural element (310A) and a second element (310B) to form a fillet (330A) at an intersection of the first structural element and the second element, positioning an inflatable radius filler (350) in the fillet, positioning the composite part in a vacuum chamber (300), venting the inflatable radius filler (350) to an environment external to vacuum chamber (300), drawing a vacuum in the vacuum chamber (300), and curing the composite part.