Composite Part Manufacturing with Vapor Filtering Layers
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Solution Overview
Problem
The manufacturing of structural composite parts for motor vehicles faces issues with excessive pressure causing panel unusability due to crushed spacers and water vapor disrupting bonding, leading to imperfect cross-linking and high porosity, which degrades mechanical performance.
Innovation Solution
Incorporating porous water vapor filtering layers in the molding process to evacuate water vapor and maintain optimal resin humidity, along with using unidirectional webs and controlled air gaps to prevent excessive pressure and ensure proper bonding.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If compression pressure is increased to improve bonding between skins and spacer, then bonding strength is improved, but the spacer is crushed and the panel becomes unusable
Solution Approach 1:
A release film is introduced as an intermediary element between the composite stack and the heating mold. This film allows water vapor to escape during heating while preventing direct contact between the resin and the mold surface, enabling bonding without requiring excessive compression pressure that would crush the spacer
2Ease of manufacture
If water-based thermosetting resin is used to improve ease of manufacture, then impregnation is facilitated, but water vapor disrupts bonding and causes local spacer sagging
Solution Approach 1:
The harmful water vapor is extracted from the system by providing escape paths through the release film and mold design. This allows the use of water-based resin for easy impregnation while removing the water vapor before it can disrupt bonding or cause spacer sagging
Solution Approach 2:
The release film acts as a mediator that permits water vapor escape while maintaining the bonding interface, allowing water-based resin to be used without the harmful effects of water vapor accumulation
3Reliability
If initial water content is reduced to prevent vapor disruption, then bonding is improved, but cross-linking is imperfect due to insufficient water for molecular mobility
Solution Approach 1:
The resin is pre-conditioned with an optimal amount of water before stacking to ensure proper cross-linking chemistry can occur. During heating, this water is then allowed to escape through the release film, preventing vapor disruption while ensuring complete cross-linking
4Device complexity
If water vapor is trapped during compression, then moisture control is simplified, but porosity increases and mechanical performance degrades
Solution Approach 1:
The release film serves as a mediator that enables water vapor escape without requiring complex moisture control systems. This maintains low porosity and high mechanical performance while keeping the process relatively simple
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 method produces composite parts with high density and low porosity, enhancing mechanical performance while avoiding the need for precise moisture control and expensive spacers, resulting in high-performance panels at a lower cost.
Implementation Method 1
the first and the second filter layers being porous to water vapor and relatively less porous to thermosetting resin
Implementation Method 2
a step of compression and heating of the stack by the heating mould, the heating being carried out at a temperature and for a duration allowing polymerization or crosslinking of the thermosetting resin
Implementation Method 3
when the thermosetting resin is water-based and/or generates water during its polymerization or cross-linking, this water in the form of vapor can disturb the bonding
Data Source
Figure 1~3
AI summary
The invention relates to a method for producing a composite part (10), said method comprising the following steps: - a step of stacking a first mat (12A), a spacer (14) and a second mat (12B) in a heatable mould (30); at least one of the mats comprising a continuous web (20) of fibres impregnated with a thermosetting resin (21); - a step involving compression and heating of the stack by the heatable mould, in order to polymerize the thermosetting resin. The stacking step comprises the deposition, in a heatable mould, of a first (22A) and a second (22B) filtration layer, in contact respectively with the first and second mats, on the opposite side from the spacer. The filtration layers are porous to steam and relatively less porous to the thermosetting resin. The heatable mould comprises means (36) for evacuation of steam (37) formed during the compression and heating step.