Fibre Composite Moulding With Precompression for Uniform Pressure
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Solution Overview
Problem
Existing membrane presses struggle to achieve uniform pressure distribution on complex geometries of fibre composite parts, particularly on the side facing away from the membrane due to limited deformability and thermal expansion differences.
Innovation Solution
The method involves compressing the workpiece before pressing by matching the workpiece volume to a smaller initial working space volume, ensuring prestressing, and using a metal membrane with a cavity for a working medium to apply pressure and temperature uniformly.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If a membrane press is used to manufacture fibre composite parts, then uniform pressurisation can be achieved on the membrane side, but uniform pressure distribution cannot be ensured on the side facing away from the membrane due to limited membrane deformability and thermal expansion differences
Solution Approach 1:
The tool is divided into two independent pressing tools: a first pressing tool with a membrane for applying uniform pressure on one side, and a second pressing tool without a membrane for the opposite side. This segmentation allows each tool to be optimised for its specific function, resolving the contradiction between uniform pressure distribution and adaptability to complex geometries.
Solution Approach 2:
Different pressing tools are designed with different properties: the first pressing tool has a membrane providing uniform pressure distribution, while the second pressing tool has a rigid structure providing mechanical support and geometry adaptation. This local differentiation allows each component to excel at its specific task without compromising the other.
2Ease of operation
If the working space volume is larger than the workpiece volume, then the workpiece can be easily inserted, but pressure drops occur during thermal expansion preventing uniform pressurisation
Solution Approach 1:
The workpiece is pre-compressed by reducing the working space volume to be smaller than the workpiece volume before heating begins. This preliminary compression ensures that when thermal expansion occurs during the manufacturing process, the workpiece remains in constant contact with both pressing tools, maintaining stable pressure distribution throughout the process.
3Adaptability or versatility
If reinforcement elements with complex geometry are used, then part functionality is improved, but direct membrane contact is prevented on the complex geometry side
Solution Approach 1:
The pressing system is segmented into two independent tools, allowing the membrane to exclusively serve the side requiring uniform pressure distribution while the other side with complex geometry is handled by the rigid pressing tool, eliminating the conflict between membrane deformability and complex geometry accommodation.
Solution Approach 2:
The rigid second pressing tool acts as an intermediary between the membrane and the workpiece on the complex geometry side, transferring and distributing the membrane's uniform pressure to areas that the membrane cannot directly access due to geometric constraints.
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 consistent pressure distribution and prevents air inclusions, maintaining part quality by preventing pressure drops during thermal expansion, allowing for complex geometries and efficient manufacturing of fibre composite parts.
Implementation Method 1
applying pressure and/or temperature to the workpiece using the membrane
Implementation Method 2
applying pressure and/or temperature to the workpiece using the membrane
Implementation Method 3
different thermal expansion from the workpiece and therefore exhibit different expansion behaviour in the case of rising and/or falling temperatures
Data Source
AI summary
The invention relates to a method for producing molded parts from fiber composite material, including the following steps: a) providing a press having a first press tool, a second press tool and a membrane. The first press tool and the second press tool are movable relative to each other. The membrane is connected to one of the press tools, a cavity for a working medium being formed between the membrane and the press tool connected thereto, a working chamber for a workpiece being formed in the other press tool, and the volume of the working chamber being modifiable by a movement of the membrane when the press is closed, b) providing at least one workpiece having a workpiece volume. The workpiece has a matrix and fibers inserted therein, c) inserting the workpiece into the working chamber of the press, d) closing the press. The working chamber takes up a first volume, e) applying pressure and/or temperature to the workpiece by means of the membrane. The working chamber takes up a second volume, a hardened molded part being created from the workpiece, and f) opening the press and removing the molded part. In order to ensure continuous and uniform pressure distribution, according to the invention the first volume of the working chamber is smaller than the workpiece volume, and therefore the workpiece is already compressed at step d) and before step e).