Wrapped Reinforcing Cord Structure for Crimp and Bending Fatigue
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Solution Overview
Problem
Existing reinforcing cords, particularly those made of carbon fibers, suffer from crimping and bending fatigue, especially under low temperatures and bending stresses, which reduces their durability and efficiency in applications like rubber belts.
Innovation Solution
A cord design featuring a core with a higher linear density than the wrapped thread, where the thread is tightly wound around the core to prevent filament movement and deformation, enhancing resistance to crimping and bending fatigue.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If carbon fibres are used to increase stiffness and reduce weight, then tensile modulus increases and weight decreases, but elongation to break decreases to 2%
Solution Approach 1:
The invention uses a composite structure combining carbon fibres with a polymer matrix (epoxy, polyester, or vinyl ester resin). The carbon fibres provide high tensile modulus and low weight, while the polymer matrix provides ductility and elongation, creating a composite material that balances stiffness with flexibility and prevents catastrophic failure.
2Force
If carbon cord is bent with a radius of curvature of 50 mm, then the outermost portion experiences bending strain of 1.0%, but at 2% strain the cord breaks
Solution Approach 1:
The invention changes the structural parameters of the cord by specifying a diameter of 0.5-2.0 mm and using a twisted strand construction with multiple carbon fibres (12-24,000 fibres per strand). This parameter optimization reduces bending strain concentration and improves fatigue resistance while maintaining the required stiffness for the application.
3Weight of moving object
If smaller cords are used to reduce product size and weight, then fuel efficiency increases and material costs decrease, but bending strain resistance may be reduced
Solution Approach 1:
The invention optimizes the cord diameter to 0.5-2.0 mm, which is smaller than conventional cords, reducing product weight and material costs. Simultaneously, the high tensile modulus of carbon fibres (250 GPa) compensates for the reduced diameter, maintaining adequate bending strain resistance. The twisted strand construction with multiple fine fibres further enhances performance by distributing stress more effectively.
Data Source
Figure 1(a)~1(c)
Figure 2
Figure 3
AI summary
A cord for reinforcing a rubber product, comprising a core (9) and at least one thread (8) wrapped around the core, wherein the core comprises at least one strand of filaments, and wherein the linear density of the core is greater than the linear density of the thread.