Speaker
Description
Hybrid laminates are used as a lightweight material system with high specific strength in e.g. the aerospace or wind-energy industry, where fatigue loads occur over decades of service lifetime accompanied by numerous numbers of cycles, in the very high cycle fatigue (VHCF) range. Especially for safety-relevant components a thorough understanding of the fatigue behavior up to VHCF regime is necessary to estimate lifetime expectancy correctly. Hybrid laminates based on metal and fiber-reinforced polymers exhibit complex damage behavior, which affects the integrity of the entire composite structure and the mechanical properties significantly, leading to steady material degradation with progressive numbers of cycles. For thermoplastic-based hybrid laminates, which offer the possibilities of formability, recyclability and mass production due to short consolidation cycle times, the VHCF behavior is fairly unknown.
Thermoplastic-based hybrid laminates containing AA6082 aluminum alloy sheets and unidirectional glass and carbon fiber-reinforced polyamide 6 were investigated. Fatigue tests up to the VHCF regime of max. 10E8 cycles were conducted on an innovative resonant fatigue testing system offering a frequency of 1,000 Hz. A sinusoidal stress amplitude was used with a stress ratio of R = 0.1. Fatigue progress and accompanying damage evolution were monitored through combined stress-strain hysteresis analysis and temperature monitoring. To conclude onto microstructural changes, microscopic analysis of damage states after defined stiffness decreases and numbers of cycles were conducted.
The test results show the necessity of improved air cooling for maintaining thermoplastic matrix properties despite self-heating. During VHCF load the mechanical properties are influenced mostly by changes in microstructure and damage development within the aluminum alloy sheets. Compared to HCF regime the interface damage changes in terms of crack and delamination rate.
| Speaker Country | Germany |
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