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Fatigue properties and damage analysis of multifunctional metal fiber / carbon fiber reinforced polymers (MCFRP)

Mittwoch (26.06.2019)
14:46 - 14:49 Uhr

CFRP offer high strength at low density but show brittle failure behavior, poor damage tolerance and an insufficient level of electrical conductivity compared to monolithic metallic materials. Against this background the newly developed composite MCFRP combines a core of 13 multidirectional carbon fiber layers, which also serves as reference laminate, with two top- and bottom-layers in 0° and 90° orientation reinforced with metastable austenitic CrNi steel fibers. The simultaneous use of additional metal fibers for mechanical and electrical purposes is an auspicious approach to enhance the lightweight potential of conventional CFRP structures for aircraft applications. First results have shown an increased electrical conductivity and improved fatigue strength in the HCF-regime [1, 2]. A key issue for further improvements is the understanding of the impact of metal fiber reinforcement on the fatigue behavior of the new hybrid composite. Aim of the presented work is to investigate the effect of embedded steel fibers on damage progression and to introduce a time- and resource-saving concept to analyze the fatigue strength of composites with minimum experimental effort. Therefore, the damage progression is analyzed by interrupted constant amplitude tests accompanied with microscopic investigations. By analyzing the surface crack density of both composites a significant slower delamination growth of the MCFRP laminate was found. Furthermore S-N curves were derived from an empirical correlation based on stress amplitude dependence of irreversible deformation energy according to the concept proposed in [3]. The calculated S-N curves agree well with additional constant amplitude tests performed for validation.

[1] B. Hannemann, S. Backe, S. Schmeer, F. Balle, U.P. Breuer: Metal fiber incorporation in carbon fiber reinforced polymers (CFRP) for improved electrical conductivity, Materialwissenschaft und Werkstofftechnik, 2016, 47 (11), 1015-1023 DOI 10.1002/mawe.201600627

[2] S. Backe, F. Balle: High Cycle Fatigue (HCF) Behavior of Metal- and Carbon-Fiber-Reinforced Polymers and Noval Capabilities for Intrinsic Damage Monitoring, Fatigue and Fracture of Engineering Materials and structures, 2018, 1-9, DOI:10.1111/ffe.12878

[3] S. Backe, F. Balle: A novel short-time concept for fatigue life estimation of carbon (CFRP) and metal/carbon fiber reinforced polymer (MCFRP), International Journal of Fatigue, 2018, 116, 317-322, DOI: 10.1016/j.ijfatigue.2018.06.044

Weitere Autoren/Referenten:
  • Prof. Dr. Tilmann Beck
    TU Kaiserslautern
  • Prof. Dr. Frank Balle
    Albert-Ludwigs-Universität Freiburg