CF-SMC Manufacturing via Partially Split Carbon Fiber Bundles
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Solution Overview
Problem
The challenge is to manufacture a high-strength Carbon Fiber Reinforced Plastic (CFRP) using a Sheet Molding Compound (SMC) at a lower cost by partially splitting a continuous carbon fiber bundle before use.
Innovation Solution
A carbon fiber package is created by traverse-winding a continuous carbon fiber bundle on a bobbin, where the bundle is partially split into sub-bundles, and the width of the original bundle is less than the total sum of the sub-bundles' widths, allowing for efficient manufacturing of CF-SMC.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If a continuous carbon fiber bundle with large filament number is used, then manufacturing cost is reduced, but strength of the CFRP product deteriorates
Solution Approach 1:
The continuous carbon fiber bundle is partially split into multiple sub-bundles during the winding process. This segmentation allows the use of large filament number bundles (lower cost) while creating smaller effective filament numbers in the final product (higher strength). The bundle is divided into sub-bundles with smaller filament numbers that provide better reinforcement while maintaining cost effectiveness.
2Strength
If the continuous carbon fiber bundle is partially split into sub-bundles, then strength of CFRP is improved, but device complexity increases
Solution Approach 1:
The splitting of the carbon fiber bundle is performed in advance during the winding process before the actual molding. The bundle is partially split into sub-bundles as it is being wound onto the bobbin, so that when the SMC is later manufactured and molded, the smaller filament number structure is already in place to provide enhanced strength without requiring additional splitting steps afterward.
Solution Approach 2:
The splitting operation is merged with the winding operation into a single integrated process step. Rather than separating the splitting and winding into distinct stages, the bundle is split and wound simultaneously, reducing overall process complexity while achieving the desired filament number reduction for improved strength.
3Productivity
If the width of continuous carbon fiber bundle is made smaller than total sum of sub-bundles widths, then manufacturing efficiency is improved, but manufacturing precision requirements increase
Solution Approach 1:
The bundle width is intentionally made smaller than the total sum of sub-bundle widths, creating a deliberate gap or overlap configuration. This partial action approach allows for easier manufacturing and better packing efficiency while the specific width relationship (smaller than total sum) provides a clear control target that balances precision requirements with manufacturability.
Data Source
Figure 1
Figure 2A
Figure 2B~3
AI summary
Provided is a useful improvement in a manufacturing method of a CF-SMC using a partially split continuous carbon fiber bundle. The manufacturing method of an SMC of the present invention includes (i) a step of drawing out a continuous carbon fiber bundle (10) from a package, the continuous carbon fiber bundle (10) having a filament number of NK and partially split into n sub-bundles in advance, (ii) a step of chopping the continuous carbon fiber bundle (10) drawn out from the package with a rotary cutter (234) into chopped carbon fiber bundles (20), and (iii) a step of depositing the chopped carbon fiber bundles (20) on a carrier film (41) traveling below the rotary cutter (234) to form a carbon fiber mat (30). In the manufacturing method, due to a fragmentation processing, in which at least some of the chopped carbon fiber bundles before being deposited on the carrier film (41) are fragmented by being brought into contact with a rotating body, a distribution of the filament number of the chopped carbon fiber bundles in the carbon fiber mat (30) is made different from that when the fragmentation processing is not performed.