Prepreg Preform Incisions for Composite Molding Defects
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Conventional preforms used in press molding for fiber-reinforced resin molded articles with thickness changes face challenges such as fiber stretching, mold closure issues, resin-rich areas, uneven thickness, and voids, leading to compromised mechanical properties and production efficiency.
Innovation Solution
A preform is created by stacking prepreg cut materials with regularly distributed first incisions and a longer second incision in specific regions, which enhances material flow and fiber alignment, allowing for improved fillability and reduced fiber bridging.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If a conventional preform with identical shape prepreg cut materials is used, then productivity is excellent, but fiber stretching occurs at thickness change parts causing poor shape following and mold closure issues
Solution Approach 1:
The patent applies local quality by making the prepreg cut materials have different shapes rather than identical shapes. Specifically, at least one prepreg cut material has a shape that corresponds to a thick wall portion of the molded article, while others have shapes corresponding to thin wall portions. This local differentiation allows each prepreg layer to properly follow the local geometry of the mold cavity, preventing fiber stretching at thickness change parts while maintaining high productivity.
2Manufacturing precision
If prepreg cut materials with openings or notches are used to follow thin wall portions, then shape following improves, but material yield decreases and production time increases
Solution Approach 1:
Instead of using openings or notches in all prepreg cut materials, the patent applies local quality by assigning different shapes to different prepreg layers based on their position in the stack. Only specific prepreg cut materials corresponding to thick wall portions have extended shapes, while others maintain standard shapes. This eliminates the need for time-consuming opening/notching operations on all layers while still achieving excellent shape following in thin wall portions.
3Ease of operation
If SMC is disposed only in thick wall portions, then fill ability improves, but resin shrinkage causes warping and mechanical properties deteriorate
Solution Approach 1:
The patent applies parameter changes by systematically varying the shape parameters of prepreg cut materials across different layers of the preform. By changing the shape of prepreg cut materials to correspond to different wall thickness regions, the patent achieves uniform resin distribution and fiber alignment throughout the molded article. This eliminates resin shrinkage-induced warping while maintaining excellent fill ability, and preserves mechanical properties by ensuring continuous fiber reinforcement throughout the structure rather than concentrating SMC only in thick wall portions.
Data Source
Figure 1(a)~1(d)
Figure 2(a)~2(c)
Figure 3(a)~3(d)
AI summary
The present invention provides a preform which is obtained by stacking two or more prepreg cut materials, each of which is obtained by cutting a sheet-like prepreg into an outline of a predetermined shape, and the sheet-like prepreg being formed of a matrix resin and reinforcing fibers aligned in one direction. This preform is characterized in that at least one prepreg cut material has first incisions that are regularly distributed throughout the whole in-plane region and a second incision that is longer than the first incision while being provided only in a predetermined specific region. The present invention also provides a method for producing this preform. In case where a fiber-reinforced resin molded article, which specifically has a product shape with a thickness change, is obtained by press molding with use of this preform, the present invention enables the achievement of a molded article having excellent mechanical properties with excellent material yield and excellent production efficiency, while exhibiting high fill ability of a molding material into a cavity. Especially in case where an article with thickness change or an article having a complicated three-dimensional shape is molded, the present invention is capable of easily avoiding the problem of the occurrence of bridging of fibers, a resin-rich part or warping.