Carbon Fiber Bundle Segmentation for SMC Mechanical Property Retention
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Solution Overview
Problem
The mechanical properties of fiber-reinforced composite materials produced using sheet molding compounds (SMC) with thick carbon fiber strands are compromised, leading to decreased strength and elastic modulus, as the increased number of filaments in the strands results in inferior molding performance.
Innovation Solution
A continuous carbon fiber bundle with a specific fineness range and roundness is developed, combined with a matrix resin composition, to produce an SMC that maintains mechanical properties while allowing for cost-effective production and improved fluidity during molding.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If thick carbon fiber strands (10,000 filaments or more) are used to reduce production cost, then cost decreases, but mechanical properties (strength and elastic modulus) of the composite material deteriorate
Solution Approach 1:
The invention divides thick carbon fiber strands into multiple bundles, where each bundle contains a controlled number of filaments (5,000-10,000). This segmentation allows the use of cost-effective thick strands while maintaining mechanical properties by ensuring each bundle has sufficient filament density for strength but not so many that they become difficult to impregnate and mold properly.
Solution Approach 2:
The invention changes the structural parameters of carbon fiber reinforcement by specifying the number of bundles and filaments per bundle. By controlling these parameters (number of bundles × filaments per bundle = total filaments), the invention achieves both cost-effectiveness and mechanical performance optimization.
2Strength
If continuous fibers are used to maintain mechanical properties, then strength and rigidity are improved, but the ability to form complicated shapes with fine irregularities deteriorates
Solution Approach 1:
The invention segments continuous carbon fiber strands into multiple manageable bundles that can be more easily handled and molded into complicated shapes while still providing continuous fiber reinforcement for mechanical strength.
Solution Approach 2:
The invention transitions from using single continuous strands to using multiple bundles of continuous fibers, adding a new dimensional aspect (bundle structure) that enables both complex shaping and mechanical property retention.
3Ease of manufacture
If the number of filaments in carbon fiber strand increases to reduce cost, then production cost decreases, but the strength and elastic modulus of the composite material decrease
Solution Approach 1:
The invention segments the total number of filaments into multiple bundles with controlled filament counts, ensuring that each bundle has optimal filament density for maintaining elastic modulus while the overall structure remains cost-effective.
Data Source
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AI summary
The present invention relates to a continuous carbon fiber bundle that is easily divided by cutting to a length of 25.4 mm, a sheet molding compound (SMC), and a fiber-reinforced composite material to be molded using the same. The SMC includes carbon fiber bundles including carbon fibers with a single fiber fineness of 1.0 dtex or more and 2.4 dtex or less and a matrix resin composition. In the SMC, a mode value in a mass distribution of carbon fiber bundles with respect to a mass of individual carbon fibers bundle is 50% or less of the mass of the carbon fiber bundle with the largest mass, and additionally, a fiber-reinforced composite material molded using the same is used to address problems.