Co-Cured Duct Stringer Bulkhead for Simpler Composite Assembly

Solution Overview

Problem

Existing duct stringer manufacturing methods, such as those described in US 2015/0239570, rely on secondary-bonded joints with adhesives different from the materials being bonded, which can complicate assembly and are not as straightforward as co-cured or co-bonded joints where the adhesive is the same material as the adherends.

Innovation Solution

The duct stringer employs co-cured or co-bonded joints where the bulkhead and duct walls are adhered using the same material as the adhesive, allowing for simpler assembly and integration, potentially using pre-preg composite materials or dry-fibre parts co-infused with matrix material, enabling the duct stringer to be assembled in an un-cured or partially cured state.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Ease of manufacture

If secondary-bonded joints with different material adhesives are used, then the duct stringer can be assembled with pre-manufactured components, but the assembly process becomes more complex and structurally less integrated

Engineering Contradiction:

Improveease of assemblyVSAvoidassembly complexity

Core Design Contradiction:

Ease of manufactureVSDevice complexity

Solution Approach 1:

The bulkhead and duct walls are merged into a single integrated structure through co-curing, where both components are cured simultaneously in an uncured state. This eliminates the need for separate assembly steps and different material adhesives, directly resolving the contradiction by combining manufacturing and assembly into one process.

Inventive Principle:

Principle #5Merging (Combining)

Solution Approach 2:

The material state parameter is changed from cured to uncured during assembly, allowing the bulkhead and duct walls to be joined in a pliable state and then cured together. This parameter change enables simpler assembly while achieving integrated structural bonding, addressing both ease of manufacture and reduced complexity.

Inventive Principle:

Principle #35Parameter changes

2Ease of manufacture

If secondary-bonded joints are used, then the duct stringer can be manufactured with separate components, but the structural integrity and integration are reduced

Engineering Contradiction:

Improvemanufacturing flexibilityVSAvoidstructural integrity

Core Design Contradiction:

Ease of manufactureVSStrength

Solution Approach 1:

The bulkhead and duct walls are merged into a single integrated structure through co-curing, where both components are cured simultaneously in an uncured state. This eliminates the need for separate assembly steps and different material adhesives, directly resolving the contradiction by combining manufacturing and assembly into one process.

Inventive Principle:

Principle #5Merging (Combining)

Solution Approach 2:

The invention uses composite material technology where the bulkhead and duct walls are made from fiber-reinforced materials that are co-cured together. This creates a homogenous composite structure with superior structural integrity compared to secondary-bonded joints, while still allowing for manufacturing flexibility through pre-forming the components.

Inventive Principle:

Principle #40Composite materials

3Device complexity

If co-cured or co-bonded joints are used, then the assembly process is simplified and structural integrity is enhanced, but the manufacturing process requires simultaneous curing of multiple components

Engineering Contradiction:

Improveassembly simplicityVSAvoidmanufacturing process complexity

Core Design Contradiction:

Device complexityVSEase of manufacture

Solution Approach 1:

The bulkhead and duct walls are merged into a single integrated structure through co-curing, where both components are cured simultaneously in an uncured state. This eliminates the need for separate assembly steps and different material adhesives, directly resolving the contradiction by combining manufacturing and assembly into one process.

Inventive Principle:

Principle #5Merging (Combining)

Solution Approach 2:

The components are prepared in advance in an uncured state, allowing for easy positioning and assembly before the simultaneous curing process. This preliminary preparation reduces the complexity of the curing process itself, as all components are ready to be joined in a single operation.

Inventive Principle:

Principle #10Preliminary action

4Stability of the object's composition

If the duct stringer is assembled in a cured state, then the components are structurally stable, but the assembly becomes more difficult and time-consuming

Engineering Contradiction:

Improvecomponent stabilityVSAvoidease of assembly

Core Design Contradiction:

Stability of the object's compositionVSEase of operation

Solution Approach 1:

The material state parameter is changed from cured to uncured during assembly, allowing the bulkhead and duct walls to be joined in a pliable state and then cured together. This parameter change enables simpler assembly while achieving integrated structural bonding, addressing both ease of manufacture and reduced complexity.

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The invention transitions the material from a static cured state to a dynamic uncured state during assembly, allowing for flexible positioning and integration. After assembly, the material returns to a stable cured state, combining the benefits of both states in the manufacturing process.

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 simplifies the assembly process and enhances the structural integrity of the duct stringer by using co-cured or co-bonded joints, allowing for easier integration with aircraft or vehicle skins, while maintaining fluid transport functionality.

Implementation Method 1

the bulkhead is adhered to the duct walls by one or more co-cured or co-bonded joints

Methodology Applied

Scientific EffectAdhesive bonding: Adhesive

Implementation Method 2

the adhesive is the same material as the bulkhead and/or the duct walls (the adherends)

Methodology Applied

Scientific EffectComposite material bonding: Composite Materials

Implementation Method 3

A co-cured joint is a joint in which the adhesive and the adherends have been cured together in a single curing process

Methodology Applied

Scientific EffectCuring:

Implementation Method 4

the co-cured joint(s) may be formed by providing the duct and the bulkhead as dry-fibre parts, co-infusing them with matrix material

Methodology Applied

Scientific EffectCo-infusion:

Data Source

PatentUS11465731B2Duct stringer with bulkhead

Publication Date: 2022.10.11 AIRBUS OPERATIONS LTD

AI summary

A duct stringer has duct walls providing a duct with a closed cross-section; and a bulkhead in the duct. The duct is adapted to transport fluid, and the bulkhead is adapted to block the flow of fluid along the duct. The bulkhead is adhered to the duct walls by one or more co-cured or co-bonded joints. The bulkhead includes a pair of bulkhead parts, each with a web and one or more flanges. The duct stringer is manufactured by positioning the mandrels end-to-end with the bulkhead parts back-to-back between them; wrapping or laying-up the duct walls around the bulkhead parts and the mandrels; co-curing or co-bonding the flanges of the bulkhead parts to the duct walls; and after the bulkhead has been adhered to the duct walls, removing the mandrels from opposite ends of the duct.