Co-Cured Duct Stringer Bulkhead for Simpler Composite Assembly
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Solution Overview
Problem
Existing duct stringer manufacturing methods, such as those using secondary-bonded joints, are complex and difficult to assemble, particularly when using composite materials, as they require different materials for bonding and may not allow for curing in an un-cured or partially cured state.
Innovation Solution
The use of 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 curing in an un-cured or partially cured state, and optionally using composite materials like fibre-reinforced composites for the duct stringer and bulkhead.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If secondary-bonded joints are used to adhere the bulkhead to the duct walls, then the bonding process can use different materials for bonding, but the assembly process becomes complex and difficult to assemble
Solution Approach 1:
The patent applies homogeneity by using the same composite material for both the bulkhead and duct walls, eliminating the need for separate bonding agents. The bulkhead and duct are co-cured together as a single integrated structure, where the matrix material of the composite itself provides the bonding function, thereby simplifying the assembly process while maintaining material compatibility.
Solution Approach 2:
The invention merges the bulkhead and duct walls into a single co-cured structure, where the bonding interface is integrated into the curing process itself. Rather than separately bonding pre-cured components, the bulkhead and duct are formed together in one curing cycle, eliminating the secondary bonding step and reducing assembly complexity.
2Reliability
If secondary-bonded joints are used with bonding agents, then bonding can be achieved, but the curing process cannot be performed in an un-cured or partially cured state
Solution Approach 1:
The patent applies preliminary action by placing the bulkhead into the duct while both are in an un-cured or partially cured state, before the final curing process. This allows the components to be positioned and integrated early in the manufacturing process, enabling subsequent co-curing that creates a reliable bond without requiring separate bonding steps after curing.
Solution Approach 2:
The invention utilizes parameter changes by transitioning the composite material from an un-cured or partially cured state to a fully cured state through controlled curing processes. This allows the bulkhead and duct to be assembled in a flexible, un-cured state and then transformed into a rigid, bonded structure through thermal or chemical curing, providing manufacturing flexibility while ensuring bonding reliability.
3Ease of operation
If co-cured or co-bonded joints are used, then the assembly process is simplified and curing in un-cured state is enabled, but the same material must be used for adhesive and adherends
Solution Approach 1:
The patent applies universality by using the composite material's matrix component to serve dual functions: as the structural matrix of the composite itself and as the bonding adhesive. The matrix material provides both structural integrity to the bulkhead and duct while simultaneously creating the bonded joint between them, eliminating the need for separate adhesive materials and simplifying the overall material system.
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, enables easier integration of duct stringers into structures like aircraft wings, and provides a robust fluid transport system with reduced complexity in bonding processes, enhancing the structural integrity and fluid management capabilities.
Implementation Method 1
the bulkhead is adhered to the duct walls by one or more co-cured or co-bonded joints
Implementation Method 2
Co-cured or co-bonded joints are advantageous compared with the secondary-bonded joints of US 2015/0239570 because they are simpler. They also enable the duct stringer to be assembled in an un-cured or partially cured state
Implementation Method 3
Optionally the duct stringer and the bulkhead are made of composite material, such as a fibre-reinforced composite material
Data Source
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AI summary
A duct stringer (20, 30) has duct walls (26) providing a duct (45) with a closed cross-section; and a bulkhead (21) 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 (70). The bulkhead comprises a pair of bulkhead parts (21 a, b), each with a web (50) and one or more flanges (51). The duct stringer is manufactured by positioning the mandrels (60) 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.