In the realm of materials science, the fatigue behavior of Liquid Silicone Rubber (LSR) has long been a focal point of attention across numerous industries. From life sciences equipment to automotive components, from consumer electronics to industrial and special applications, a deep understanding of the fatigue characteristics of LSR is crucial for optimizing product design and enhancing product performance.
An In – Depth Analysis of LSR’s Fatigue Behavior
The fatigue properties of LSR are extremely sensitive to cyclic load limits and a multitude of influencing factors. Different factors exert unique effects on its fatigue behavior, and the load history can reflect the associated mechanical severity.
Environmental factors play a pivotal role in the fatigue process of LSR, affecting both short – term and long – term fatigue behavior. Additionally, compound factors such as silicone type, filler type, and volume fraction significantly influence the fatigue performance of LSR.
Within the system of silicone materials, mechanical fatigue is defined as the gradual weakening of physical properties due to the slow propagation of cracks under dynamic loads or deformations. The progressive decrease in stiffness is the most intuitive manifestation of this. During the fatigue process, various complex phenomena occur at the atomic and molecular levels. Due to the complexity of its structure, the fatigue characteristics of LSR are empirical in some grades.
To evaluate and simulate the repeated deformations that LSR products endure in actual use, researchers have developed a variety of testing methods. These deformation forms include tension, compression, bending, or combinations of multiple deformations. Among them, the flex fatigue test is the most widely used. This test applies a static load over multiple cycles and then calculates parameters such as peak load, elongation percentage, modulus of elongation, and yield strength at break. The test adheres to the ASTM D623 and ASTM D430 standards.
The curves obtained from the experiments correlate the load with the strain and present different degrees of cyclic conditions. Notably, there is a significant difference between the loading and unloading curves, forming a hysteresis loop.
Numerous factors influence the mechanical fatigue life of LSR components. Among them, load history, environmental impacts, and silicone formulations are the three major factors. A thorough exploration of these factors is conducive to the development of more durable LSR components and enables the analysis and prediction of product failures.
A Comprehensive Exploration of Key Influencing Factors
Load History
Mechanical fatigue is often accompanied by crack nucleation and propagation caused by fluctuating loads. In practical applications, the different load – change patterns that components experience directly affect the generation and development process of cracks, thereby determining their fatigue life.
Environmental Conditions
Environmental factors play a crucial role in the fatigue process, especially during long – life cycles. Temperature has a particularly significant impact on the fatigue of LSR. Research data shows that when the temperature is below 0°C, there is a clear difference in stiffness between – 40°C and – 20°C. When the temperature is above 0°C, the degree of hysteresis and stress softening gradually decreases as the temperature rises. The effect of temperature on stress softening stabilizes at 60°C. However, in the test at 150°C, the sample failed before the end of the experiment, resulting in an incomplete test.
Silicone Formulations
Generally speaking, traditional LSR does not have a significant advantage over organic rubbers in resisting dynamic stress. However, with the continuous development of materials science, several enterprises have successfully developed new materials. Their fatigue – resistance performance is 8 to 20 times higher than that of traditional silicone materials. The emergence of these new materials has brought new development opportunities to many industries.
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