Rigid Insert Retainer for Composite Fuselage Mandrel Flatness
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Solution Overview
Problem
In the manufacture of composite fuselage components, maintaining flatness tolerances during the formation process on a mandrel is challenging, often requiring rework and shimming due to surface waviness caused by flexible pneumatic tooling, which can lead to inconsistencies in the finished structure.
Innovation Solution
A method and apparatus using a rigid elongated insert with a retainer, matching the thermal properties of the mandrel and composite material, is positioned adjacent to a flexible pneumatic tool within the mandrel cavity to maintain flatness tolerances, ensuring a consistent tool surface and reducing the need for post-cure rework and shimming.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If a flexible pneumatic tool (bladder) is used to fill the trough on the mandrel, then the tool can conform to the mandrel shape and accommodate composite material placement, but the tool surface becomes non-rigid and depresses under compression, resulting in surface waviness and loss of flatness tolerances
Solution Approach 1:
A rigid retainer member is introduced as an intermediary between the flexible pneumatic tool and the composite material. The retainer has a bearing surface that contacts the composite material and a tapered surface that contacts the pneumatic tool, transferring compressive loads from the material to the tool through a controlled interface that prevents direct compression of the flexible tool surface.
Solution Approach 2:
The rigid retainer member acts as a counterbalancing element that opposes the flexibility of the pneumatic tool. By providing a rigid bearing surface, it counteracts the tool's tendency to deform under compression, maintaining the required flatness tolerance during composite material placement and curing.
2Manufacturing precision
If a rigid tool surface is used to maintain flatness tolerances, then surface waviness is prevented, but the tool cannot conform to the mandrel shape or accommodate the flexible pneumatic tooling
Solution Approach 1:
The retainer member provides a rigid bearing surface locally at the interface with the composite material where flatness is critical, while the tapered contact surface interfaces with the flexible pneumatic tool. This local differentiation of rigidity allows the system to maintain precision where needed while preserving overall flexibility for conformability.
3Ease of manufacture
If the pneumatic tool directly contacts the composite material, then material placement is simplified, but the flexible tool surface deforms under application loading, causing inner mold line flatness deviations
Solution Approach 1:
The retainer member serves as an intermediary bearing surface between the composite material and the pneumatic tool. The bearing surface provides a rigid interface for material placement while the tapered surface transfers loads to the flexible tool, preventing direct compression that would cause surface deformation and flatness deviations.
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 solution provides a consistent tool surface, maintains flatness tolerances, reduces rework and shimming requirements, and enhances production efficiency by ensuring accurate alignment and assembly of composite structures without secondary adjustments.
Implementation Method 1
The retainer is constructed of a material which matches the thermal properties of the applied composite material and mandrel tool
Data Source
AI summary
An apparatus for use in formation of a composite structure about a mandrel. A generally flexible pneumatic tool and a generally rigid insert are inserted end to end in a cavity of the mandrel. A first end of the insert is positioned in the cavity, adjacent the pneumatic tool, and defines an interface therebetween. The retainer is connected to the insert proximate the first end of the insert. The retainer has an end that extends outwardly from the first end of the insert across the interface and over a portion of the end of the pneumatic tool. The uppermost surfaces of the insert, retainer, and pneumatic tool are generally flush with one another and facilitate a smooth surface being formed over such uppermost surfaces as the composite material is wound about the mandrel in the formation of the composite structure.