Variable H-Section Composite Beam Manufacturing
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Solution Overview
Problem
Current methods for manufacturing composite aircraft beams with variable H-sections face issues of non-uniform pressure application due to imperfect connections between metal moulds and the beam, leading to defects like porosity and thickness variations, especially in areas with non-rectilinear profiles.
Innovation Solution
The method employs flexible inserts wrapped in tubular bags with breather layers and sealed with release films, supported by discrete standards, to ensure uniform pressure application in an autoclave, eliminating the need for rigid metal tools and allowing precise shaping of beams with variable thickness and profiles.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Shape
If rigid metal moulds and counter-moulds are used to manufacture composite beams, then the beam can be given its final shape, but non-uniform pressure is applied leading to porosity and thickness variations
Solution Approach 1:
The patent replaces rigid metal moulds with flexible vacuum bags that conform to the beam's variable cross-section. The vacuum bag is sealed around the beam and connected to a vacuum source, creating uniform atmospheric pressure distribution across the entire beam surface during curing, eliminating pressure concentration points and porosity defects while maintaining precise geometric shaping.
Solution Approach 2:
The patent substitutes the mechanical contact pressure system of rigid metal tools with a vacuum pressure system. Instead of relying on mechanical force transmission through tool contacts, the system uses vacuum to create uniform atmospheric pressure distribution, eliminating the problems of imperfect connections and non-uniform pressure application inherent in mechanical systems.
2Stability of the object's composition
If rigid metal tools are used, then the beam can be supported during curing, but imperfect joints create empty spaces causing resin flow and thickness reduction
Solution Approach 1:
The flexible vacuum bag provides continuous support along the entire beam length without joints or connection points. The bag conforms to the variable cross-section and maintains stable support during curing through vacuum adhesion, eliminating empty spaces where resin could flow and causing thickness reduction.
Solution Approach 2:
The vacuum bag acts as an intermediary between the atmospheric pressure and the beam surface, distributing pressure uniformly across the entire surface area. This intermediary layer eliminates direct contact between rigid tools and the beam, preventing resin leakage through imperfect joints while maintaining thickness uniformity.
3Shape
If variable cross-section beams are manufactured with rigid tools, then specific geometries can be achieved, but geometric precision is compromised in variable thickness areas
Solution Approach 1:
The vacuum bag is designed to conform to the variable cross-section geometry of the beam, with its flexible nature allowing it to adapt to changing dimensions along the beam length. This ensures uniform pressure application across all sections, maintaining geometric precision even in areas with variable thickness or non-rectilinear profiles.
Solution Approach 2:
The system changes the pressure application method from mechanical contact (rigid tools) to vacuum pressure (flexible bag), allowing the pressure distribution to adapt to varying beam geometries. This parameter change enables precise shaping of variable cross-section beams while maintaining uniform pressure and geometric precision throughout.
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 ensures high geometrical precision, reduces porosity and lamination defects, lowers production costs, and offers a wider design range for lighter aircraft components, with a 10% cost reduction compared to conventional methods.
Implementation Method 1
a combination of heat and pressure is applied with a predetermined variation over time. The pressure applied to the vacuum bag is discharged on to the metal parts of the tools, which in turn transmit the pressure to the spar. As a result of this compaction, the pressure, combined with the simultaneous temperature increase, consolidates and cures the resin.
Implementation Method 2
All of these elements are then enclosed in what is known as a 'vacuum bag', made from polyamide (nylon) film to which a vacuum is applied. During the step of curing in an autoclave, pressure is applied to the outer surfaces of the upper and lower skins and to the lower flanges of the spars so as to compact them against the corresponding plates of the tool
Data Source
AI summary
A beam of fiber-reinforced curable thermosetting composite material is preliminarily assembled in an uncured condition. The beam is placed between two forming tools, namely a lower and an upper tool, shaped in such a way as to give the lower and upper flanges a predetermined shape, at least one of the flanges having a non-rectilinear profile viewed in a longitudinal vertical plane. Two longitudinally elongate rigid inserts are placed between the flanges at the sides of the web and are covered in respective airtight tubular bags. The spaces between the upper tool and the lower tool on the two opposite longitudinal sides are sealed. The open opposite ends of the tubular bags are also sealed in such a manner that the pressure applied in an autoclave during the step of curing causes the tubular bags to swell and presses them against the two opposite faces of the web and against the flanges of the beam. On completion of curing, the upper forming tool is removed and the inserts are extracted sideways.