Influence of particle and short-fibre reinforcement on the very high cycle fatigue behaviour of aluminium matrix composites. (August 2018)

• Record Type: Journal Article
• Authors: Illgen, A.; Weidner, A.; Biermann, H.
• Is Part Of: International journal of fatigue. Volume 113(2018)
• Page Start: 299
• Page End: 310
• Publication Date: 2018-08
• Subjects: Very high cycle fatigue -- Aluminium matrix composites -- Short-fibre reinforced -- Particle-reinforced; Materials -- Fatigue -- Periodicals; Materials -- Fatigue; Periodicals; 620.1122
• DOI: 10.1016/j.ijfatigue.2018.04.025
• Languages: English
• ISSNs: 0142-1123

Abstract

Highlights: The fatigue behaviour of aluminium matrix composites reinforced by alumina particles or short-fibres was investigated in the very high cycle fatigue regime. Fatigue tests were complemented by in situ thermographic measurements and by recording the resonance frequency (fres ) and the nonlinearity parameter (βrel ). No influence of test frequency was found. In VHCF-region marginally higher fatigue life can be measured for the two reinforced materials. Both reinforced materials show multiple crack initiation and damage after fatigue tests. High deformation and microcracks are often localized in areas of fibre/particle agglomeration. Short-fibre reinforced specimens with an overaged heat treatment show in all tests more than one hot spot. Abstract: The fatigue behaviour of aluminium matrix composites (Al-MMCs) reinforced by alumina particles (15 vol% Al2 O3 ) or short-fibres (20 vol% Saffil), respectively, was investigated in the very high cycle fatigue (VHCF) regime at stress amplitudes ≤140 MPa to reach fatigue lives of up to 10 10 cycles using an ultrasonic fatigue testing device. Fatigue tests were complemented by in situ thermographic measurements to record the temperature of the whole specimen and to find "hot spots" indicating changes in microstructure and, therefore, the initiation or growth of cracks. Results obtained in the VHCF-region fit well with results obtained in LCF/HCF-region. A significant influence of test frequency was not found. Surprisingly, the reinforced Al-MMCs are capable to bear up to 10 9 cycles, although damage starts early during cyclic loading. In addition, although in the LCF/HCF regime the fatigue life and fatigue strength of the short-fibre reinforced Al-MMCs are significantly smaller compared to particle reinforced and unreinforced material, no significant differences to the particle-reinforced and unreinforced Al-MMC were observed at stresses below 140 MPa. Moreover, at stresses below 80 MPa not fatigue failure occurred at all up to 10 10 cycles.