TY - JOUR

T1 - Very high cycle fatigue properties of short glass fiber reinforced polyetheretherketone (PEEK)

AU - Fitzka, Michael

AU - Stadler, Gabriel

AU - Schönbauer, Bernd M.

AU - Pinter, Gerald

AU - Mayer, Herwig

N1 - Publisher Copyright: © 2024 The Authors

PY - 2025/1

Y1 - 2025/1

N2 - The fatigue properties of 14 wt-% short glass fiber reinforced polyetheretherketone (PEEK–GF14) have been investigated in the high and very high cycle fatigue (VHCF) regime. Experiments were performed at a load ratio of –1 with servohydraulic and electrodynamic equipment at cycling frequency 10–20 Hz, and with ultrasonic equipment at 19 kHz. A new specimen geometry has been developed that allows ultrasonic tests up to high stress amplitudes. The same specimen shape was used in both testing series to exclude size effects, which enabled to focus on the influence of cycling frequency and testing technique. Ultrasonic fatigue testing with intermittent loading served to avoid heating of specimens. The S-N curves measured at 10–20 Hz and 19 kHz show a similar slope exponent (i.e., 10 % deviation). Mean S-N curve determined with ultrasonic equipment is shifted to slightly lower stress amplitudes, which may be attributed to statistical scatter. PEEK–GF14 does not show a fatigue limit and failures still occurred above 109 cycles. The VHCF strength of PEEK-GF14 is approximately two times higher compared with unreinforced PEEK. Fractographic investigations revealed fiber fracture and, less frequently, fiber pull-out.

AB - The fatigue properties of 14 wt-% short glass fiber reinforced polyetheretherketone (PEEK–GF14) have been investigated in the high and very high cycle fatigue (VHCF) regime. Experiments were performed at a load ratio of –1 with servohydraulic and electrodynamic equipment at cycling frequency 10–20 Hz, and with ultrasonic equipment at 19 kHz. A new specimen geometry has been developed that allows ultrasonic tests up to high stress amplitudes. The same specimen shape was used in both testing series to exclude size effects, which enabled to focus on the influence of cycling frequency and testing technique. Ultrasonic fatigue testing with intermittent loading served to avoid heating of specimens. The S-N curves measured at 10–20 Hz and 19 kHz show a similar slope exponent (i.e., 10 % deviation). Mean S-N curve determined with ultrasonic equipment is shifted to slightly lower stress amplitudes, which may be attributed to statistical scatter. PEEK–GF14 does not show a fatigue limit and failures still occurred above 109 cycles. The VHCF strength of PEEK-GF14 is approximately two times higher compared with unreinforced PEEK. Fractographic investigations revealed fiber fracture and, less frequently, fiber pull-out.

KW - Fatigue limit

KW - Fiber reinforced polymer

KW - Frequency effect

KW - Strain rate influence

KW - Ultrasonic fatigue

UR - http://www.scopus.com/inward/record.url?scp=85206484897&partnerID=8YFLogxK

U2 - 10.1016/j.ijfatigue.2024.108652

DO - 10.1016/j.ijfatigue.2024.108652

M3 - Article

AN - SCOPUS:85206484897

VL - 190.2025

JO - International Journal of Fatigue

JF - International Journal of Fatigue

SN - 0142-1123

IS - January

M1 - 108652

ER -