Fiber-Reinforced Resin Molding Material With Layered Fiber Length Gradient
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Solution Overview
Problem
Existing fiber-reinforced resin molding materials face challenges in achieving excellent flowability and mechanical properties during molding, particularly due to poor flowability of chopped fiber bundles and uneven orientation, which leads to variations in mechanical properties and increased risk of bending and aggregation of fibers.
Innovation Solution
A fiber-reinforced resin molding material with a layered structure where the number-average fiber length, thickness, and width of chopped fiber bundles gradually increase from the outermost layer towards the innermost layer, optimizing flow resistance and impregnation, thereby improving flowability and mechanical properties.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If chopped fiber bundles are used in SMC sheet, then molding capability for complicated shapes is improved, but flowability deteriorates due to fiber bundle bending and uneven orientation
Solution Approach 1:
The fiber bundle is segmented into multiple filaments (500-12,000 filaments per bundle), which prevents excessive bending and aggregation while maintaining the bundle structure. This segmentation allows the fiber bundles to flow more smoothly during molding while still providing reinforcement.
Solution Approach 2:
Different regions of the SMC sheet have different fiber bundle characteristics. The fiber bundle thickness and width are controlled to be 0.01-0.4 mm and 0.5-60 mm respectively, creating optimal local properties for flowability while maintaining reinforcement capability throughout the sheet.
2Ease of manufacture
If fiber bundle thickness and width are reduced, then flowability is improved, but mechanical properties deteriorate due to insufficient reinforcement
Solution Approach 1:
The fiber bundle dimensions are precisely controlled within specific ranges: thickness of 0.01-0.4 mm and width of 0.5-60 mm. This parameter optimization ensures that the fiber bundles are thin enough to flow properly during molding while maintaining sufficient cross-sectional area for mechanical reinforcement.
Solution Approach 2:
The SMC sheet is a composite material combining fiber bundles with matrix resin in specific proportions (fiber content of 20-75 wt%). This composite structure allows the fiber bundles to provide reinforcement while the matrix resin ensures proper flow and bonding, achieving both flowability and mechanical strength.
3Ease of manufacture
If monofilaments are used as reinforcing fibers, then manufacturing simplicity is improved, but workability deteriorates due to fiber floating and aggregation
Solution Approach 1:
Multiple filaments are merged into a bundle structure (500-12,000 filaments per bundle), which prevents individual monofilaments from floating and aggregating during molding. The bundled structure maintains fiber position and orientation while still being manufacturable from continuous fiber bundles.
4Strength
If fiber length is increased, then mechanical properties are improved, but flowability deteriorates due to increased bending and aggregation
Solution Approach 1:
The fiber bundles are cut to a specific length range (3-100 mm) rather than using full continuous length. This partial cutting provides sufficient reinforcement while preventing excessive bending and aggregation that would occur with longer fibers, thus maintaining flowability during molding.
Data Source
AI summary
A fiber-reinforced resin molding material [C] includes a chopped fiber bundle [A] and a matrix resin [B], the material being characterized in that, when divided into n layers along the thickness direction of the fiber-reinforced resin molding material [C], the number-average fiber length [Lk] of the chopped fiber bundle [Ak] constituting each layer Fk (1≤k≤n) gradually increases from one outermost layer F1 of the fiber-reinforced resin molding material [C] toward the other outermost layer Fn. Also provided is a molded article obtained by molding the fiber-reinforced resin molding material. This fiber-reinforced resin molding material exhibits excellent flowability, and can exhibit excellent mechanical properties when made into a molded article.