Composite Holding Parts for Prepreg Fabric Hardening
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Solution Overview
Problem
The production of T-stringer-stiffened skins in the aerospace sector is hindered by the high cost and inflexibility of special steel tools used for retaining carbon fibre plastic prepreg materials during hardening, which also pose handling difficulties due to their weight and require expensive remachining for shape changes.
Innovation Solution
A method involving the use of at least partially hardened composite fibre material holding parts, which can be produced at a lower cost and with greater flexibility, replaces the expensive special steel tools by hardening at a lower temperature, allowing for the use of materials like aluminium and ensuring minimal thermal stress during the high-temperature hardening process of the prepreg fabric.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If special steel tools are used to retain prepreg fabric during hardening, then the tools provide sufficient strength and stability, but the production cost increases and the tools become difficult to handle
Solution Approach 1:
The patent changes the material parameter from special steel to composite fibre material, and changes the hardening temperature parameter from high temperature to low temperature. This allows the tools to be made from inexpensive materials while still providing sufficient strength during the low-temperature hardening process, resolving the contradiction between tool strength and production cost.
Solution Approach 2:
The patent uses composite fibre material for the tools instead of traditional metal materials. This composite material provides adequate strength for the application while being significantly cheaper and lighter than special steel, thus resolving the contradiction between strength requirements and production cost.
2Stability of the object's composition
If special steel tools are used for retaining prepreg fabric, then the tools maintain structural stability, but remachining becomes expensive when shape changes are required
Solution Approach 1:
By changing the material from special steel to composite fibre material and reducing the hardening temperature, the tools become more flexible and easier to modify. When shape changes are required, the lower cost material allows for more economical remachining or replacement, resolving the contradiction between stability and ease of repair.
3Strength
If special steel tools are used for producing wing parts, then the tools provide necessary strength, but the tool weight becomes considerable and handling becomes difficult
Solution Approach 1:
The patent replaces heavy special steel with lightweight composite fibre material for the tools. This composite material maintains sufficient strength for retaining prepreg fabric during low-temperature hardening while dramatically reducing the tool weight, making them much easier to handle and transport.
4Reliability
If tools made from material with low thermal expansion coefficient are used, then the tools resist thermal stress during hardening, but the material choice becomes limited and cost increases
Solution Approach 1:
The patent changes the hardening temperature parameter from high temperature to low temperature. This temperature reduction allows the use of materials with higher thermal expansion coefficients that are cheaper and easier to machine, while still providing sufficient thermal stress resistance for the reduced temperature range.
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 reduces production costs, simplifies machining, and enhances the structural integrity of the components by minimizing thermal stresses and enabling the use of more flexible, lower-cost tools, while maintaining the high strength and stability of the structural components.
Implementation Method 1
The at least one holding part of composite fibre material also has the advantage that it has a very similar thermal expansion coefficient to that of the composite fibre material of the unhardened prepreg fabric. Consequently there are no harmful stresses between the prepreg fabric and the at least one holding part during hardening at the high hardening temperature.
Data Source
AI summary
This invention provides a method for producing a structural component, particularly in the aerospace sector. An unhardened prepreg fabric is formed from a composite fiber material, hardenable at a first hardening temperature, into a predetermined shape. The unhardened prepreg fabric is then connected to at least one hardening part of a composite fiber material partially hardened at a second hardening temperature for holding the unhardened prepreg fabric in the predetermined shape, wherein the second hardening temperature is lower than the first hardening temperature. In a further method step the unhardened prepreg fabric connected to the at least one holding part is hardened at the first hardening temperature to form the structural component. The idea on which this invention is based consists in replacing expensive tools of special steel previously used for holding dimensionally unstable prepreg fabrics with at least one holding part of composite fiber materials, wherein the at least one holding part has a lower hardening temperature than the prepreg fabric, and can therefore be produced with a lower cost tool.