Rubber-Reinforcing Cord Structure for Predictable Fatigue Failure
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Solution Overview
Problem
Conventional rubber-reinforcing cords with high modulus fibers suffer from sudden fracture due to bending fatigue, leading to unexpected breakdown of rubber products, as the fibers break simultaneously without prior warning, making it difficult to predict and prevent such failures.
Innovation Solution
A rubber-reinforcing cord design featuring a first fiber strand with a lower tensile elastic modulus in the central portion and a plurality of second fiber strands with a higher tensile elastic modulus by 20 GPa or more in the peripheral portion, where the second fiber strands provide higher elastic modulus and resist tension, while the first fiber strand is less subjected to bending stress, delaying its breakage and allowing for prior warning of potential failure.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If high modulus fibers are used to form a rubber-reinforcing cord, then the elastic modulus is improved, but the bending fatigue resistance deteriorates
Solution Approach 1:
The patent applies local quality by using different fiber materials with different elastic moduli in different regions of the cord. The central portion uses high elastic modulus fibers (e.g., carbon fibers with 200-400 GPa) to provide high stiffness, while the peripheral portion uses low elastic modulus fibers (e.g., nylon or polyester with 2-5 GPa) to provide flexibility and bending fatigue resistance. This spatial differentiation of material properties resolves the contradiction between high elastic modulus and bending fatigue resistance.
Solution Approach 2:
The patent employs composite materials by combining high elastic modulus fibers and low elastic modulus fibers in a double-layer structure. The high modulus fiber core provides the necessary stiffness for maintaining cord shape and resisting tensile loads, while the low modulus fiber sheath provides flexibility and absorbs bending stresses. This composite structure enables the cord to simultaneously achieve high elastic modulus and excellent bending fatigue resistance.
2Reliability
If a double-layer structure with high modulus fibers in the central portion and low modulus fibers in the peripheral portion is used, then the balance between elastic modulus and bending fatigue resistance is improved, but the sudden fracture problem persists
Solution Approach 1:
The patent applies preliminary action by designing the cord structure so that the low elastic modulus fibers in the peripheral portion break first during fatigue loading, before the high elastic modulus fibers in the central portion. This sequence is engineered in advance through the selection of appropriate materials and their arrangement. When the peripheral fibers break, they provide early warning signs (visible damage, change in cord appearance) before the core fibers fail, allowing timely detection and replacement of the cord before sudden fracture occurs.
Solution Approach 2:
The patent implements beforehand cushioning by using the low elastic modulus peripheral fibers as a protective layer that absorbs and dissipates bending stresses before they reach the high elastic modulus core fibers. This outer layer acts as a cushion that protects the critical core from direct exposure to damaging stresses, delaying their failure and providing a buffer period for detection and replacement.
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 design prevents simultaneous fracture of the rubber-reinforcing cord and the rubber product, enabling prediction and prevention of equipment breakdown by providing a time lag between the breaks of the first and second fiber strands, thus maintaining the rubber product's performance and preventing sudden failure.
Implementation Method 1
the second fiber strand has a tensile elastic modulus higher than a tensile elastic modulus of the first fiber strand by 20 GPa or more
Implementation Method 2
a rubber product including: a rubber matrix; and the above rubber-reinforcing cord of the present invention, the rubber-reinforcing cord being embedded in the rubber matrix
Data Source
Figure 1~2
Figure 3
AI summary
A rubber-reinforcing cord (10) includes a first fiber strand (11) and a plurality of second fiber strands (12) disposed around the first fiber strand (11). The second fiber strand (12) has a tensile elastic modulus higher by 20 GPa or more than that of the first fiber strand (11).