Partially separated fiber bundle and method for manufacturing same, chopped-fiber bundle using same, and fiber-reinforced resin molding material
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Solution Overview
Problem
Existing methods for producing fiber bundles with a desirable number of single yarns struggle to maintain fluidity and mechanical properties during forming, as fiber bundles tend to aggregate, making it difficult to prepare a stable intermediate base material for composite materials.
Innovation Solution
A partially separated fiber bundle is created by coating the reinforcing fibers with a water-soluble polyamide, where separated and unseparated fiber sections are alternately arranged, preventing re-aggregation and allowing for adjustable fiber separation to balance fluidity and mechanical properties.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If fiber bundles are separated to increase the number of single yarns, then mechanical properties improve, but fluidity at the time of forming deteriorates
Solution Approach 1:
The fiber bundle is segmented into multiple single yarns through controlled separation, dividing the large tow into smaller units that can be better distributed during forming while maintaining adequate fluidity
Solution Approach 2:
Different sections of the fiber bundle are separated to different degrees, creating local variations in yarn count that optimize both mechanical properties in load-bearing areas and fluidity in flow-critical regions
2Adaptability or versatility
If fiber bundles are slit longitudinally to adjust the number of single yarns, then the number of single yarns can be adjusted, but bundling property deteriorates making it difficult to wind up or wind off
Solution Approach 1:
A sizing agent is applied to the fiber bundle before longitudinal slitting to maintain bundling property during the separation process, preventing the fibers from becoming too loose to be wound properly
Solution Approach 2:
The chemical properties of the fiber bundle surface are changed by applying a sizing agent, which modifies the friction and adhesion characteristics to maintain bundling integrity during and after slitting
3Ease of operation
If fiber bundles are conveyed after longitudinal slitting, then handling is improved, but branched fiber bundles wrap the guide roll or feed roll making conveyance difficult
Solution Approach 1:
A sizing agent acts as an intermediary substance between the fiber bundle and the guide rolls, reducing direct contact and friction that cause branching and wrapping during conveyance
4Ease of manufacture
If cheap large tow with great number of single yarns is used, then cost is reduced, but mechanical properties deteriorate due to poor fiber distribution
Solution Approach 1:
The fiber bundle structure is made dynamic through controlled separation at different stages, allowing the same large tow to be processed into configurations that optimize both cost-effectiveness and mechanical properties depending on the application requirements
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 stable process productivity, maintains desirable fiber bundle form, and enhances mechanical properties such as strength and elastic modulus with reduced variance in the final composite material.
Implementation Method 1
coating the reinforcing fibers with a water-soluble polyamide
Implementation Method 2
coating the reinforcing fibers with a water-soluble polyamide
Data Source
Figure 1~2(B)
Figure 3~4(B)
Figure 5~6
AI summary
A partially separated fiber bundle, a chopped fiber bundle using the same, and a fiber-reinforced resin molding material, in which a sizing agent including at least a polyamide resin is caused to adhere to the surface of reinforcing fibers in the partially separated fiber bundle, which is obtained by separated fiber sections separated into a plurality of bundles, and unseparated fiber sections, being alternately formed along the longitudinal direction of a reinforcing fiber bundle comprising a plurality of single yarns, the number of fibers per unit width contained in the reinforcing fiber bundle being at least 600 fibers/mm and less than 1,600 fibers/mm, and the drape level of the reinforcing fiber bundle being 120 to 240 mm. Also, a method for manufacturing the partially separated fiber bundle, in which are performed: a fiber separation step (A) in which a fiber-separating means having a plurality of projecting parts is inserted into the fiber bundle comprising a plurality of single yarns while the fiber bundle is caused to travel in the longitudinal direction, the fiber separation means generating a separated fiber section; an interlacing step (B) for forming interlaced sections in which a single yarn is interlaced with at least one section of a separated fiber section that contacts a projecting part; a partial fiber separation step (C) in which the fiber-separation means is taken off a fiber bundle, and after passing through an accumulated interlaced section including the interlaced section, is again inserted into the fiber bundle, alternately forming the separated fiber section that is separated into the plurality of bundles and the unseparated fiber section; and a resin impregnation step (D) for adding a water-soluble polyamide to the fiber bundle. A partially separated fiber bundle is provided having excellent process stability in chopping processes and the like, and in which productivity is improved, while preventing inappropriate re-aggregation and the like.