On the Influence of Cyclic Loading Frequency on Fatigue Limit of Short-Fiber Thermoplastics

Pharindra Pathak; Kaniz F Bristy; Vipin Kumar; Michael M Khonsari; Suhasini Gururaja

doi:10.1111/ffe.70241

On the Influence of Cyclic Loading Frequency on Fatigue Limit of Short-Fiber Thermoplastics

Pharindra Pathak
, Kaniz F Bristy
, Vipin Kumar
, Michael M Khonsari
, Suhasini Gururaja

Composites Innovation

Research output: Contribution to journal › Article › peer-review

1 Scopus citations

Abstract

This study investigates the influence of cyclic loading frequency on the fatigue limit of additively manufactured-compression molded (AM-CM) short carbon fiber thermoplastics (20 wt% CF-ABS). Accelerated fatigue characterization was performed using passive infrared thermography under a staircase loading protocol at 5, 10, 15, and 20 Hz. Displacement accumulation, stabilized surface temperature ((Formula presented.)), and fatigue fracture entropy (FFE) were jointly analyzed to capture frequency-dependent damage mechanisms. Results show a notable increase in fatigue limit from 52.14% (Formula presented.) at 5 Hz to 61.14% (Formula presented.) at 20 Hz. Higher frequencies suppressed viscoelastic deformation, reduced hysteretic energy dissipation, and shifted failure morphology from matrix-dominated cracking to fiber breakage. Constant amplitude tests at 60% (Formula presented.) confirmed these trends, with specimens failing at 5 Hz but surviving 3 million cycles at 20 Hz. Across all frequencies, FFE remained consistent (0.096 (Formula presented.) 0.0144 kJ/m (Formula presented.) K), supporting its role as a rate-independent scalar indicator of fatigue damage.

Original language	English
Pages (from-to)	2455-2464
Number of pages	10
Journal	Fatigue and Fracture of Engineering Materials and Structures
Volume	49
Issue number	6
DOIs	https://doi.org/10.1111/ffe.70241
State	Published - Jun 2026

Funding

This research was supported by the NASA EPSCoR Rapid R3 grant, NASA: 80NSSC24M0154, PI Gururaja, overseen by Dr. Trenton Ricks from NASA Glenn Research Center. This research was also supported in part by the US Department of Energy Office of Energy Efficiency and Renewable Energy (EERE) and the Advanced Materials and Manufacturing Technologies Office (AMMTO). This research was supported by the NASA EPSCoR Rapid R3 grant, NASA: 80NSSC24M0154, PI Gururaja, overseen by Dr. Trenton Ricks from NASA Glenn Research Center. This research was also supported in part by the US Department of Energy Office of Energy Efficiency and Renewable Energy (EERE) and the Advanced Materials and Manufacturing Technologies Office (AMMTO). This manuscript has been authored by UT‐Battelle, L.L.C., under contract DE‐AC05‐00OR22725 with the US Department of Energy (DOE).

Keywords

additively manufactured short fiber thermoplastics
fatigue limit
loading frequency
passive infrared thermography

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10.1111/ffe.70241

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title = "On the Influence of Cyclic Loading Frequency on Fatigue Limit of Short-Fiber Thermoplastics",

abstract = "This study investigates the influence of cyclic loading frequency on the fatigue limit of additively manufactured-compression molded (AM-CM) short carbon fiber thermoplastics (20 wt\% CF-ABS). Accelerated fatigue characterization was performed using passive infrared thermography under a staircase loading protocol at 5, 10, 15, and 20 Hz. Displacement accumulation, stabilized surface temperature ((Formula presented.)), and fatigue fracture entropy (FFE) were jointly analyzed to capture frequency-dependent damage mechanisms. Results show a notable increase in fatigue limit from 52.14\% (Formula presented.) at 5 Hz to 61.14\% (Formula presented.) at 20 Hz. Higher frequencies suppressed viscoelastic deformation, reduced hysteretic energy dissipation, and shifted failure morphology from matrix-dominated cracking to fiber breakage. Constant amplitude tests at 60\% (Formula presented.) confirmed these trends, with specimens failing at 5 Hz but surviving 3 million cycles at 20 Hz. Across all frequencies, FFE remained consistent (0.096 (Formula presented.) 0.0144 kJ/m (Formula presented.) K), supporting its role as a rate-independent scalar indicator of fatigue damage.",

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N2 - This study investigates the influence of cyclic loading frequency on the fatigue limit of additively manufactured-compression molded (AM-CM) short carbon fiber thermoplastics (20 wt% CF-ABS). Accelerated fatigue characterization was performed using passive infrared thermography under a staircase loading protocol at 5, 10, 15, and 20 Hz. Displacement accumulation, stabilized surface temperature ((Formula presented.)), and fatigue fracture entropy (FFE) were jointly analyzed to capture frequency-dependent damage mechanisms. Results show a notable increase in fatigue limit from 52.14% (Formula presented.) at 5 Hz to 61.14% (Formula presented.) at 20 Hz. Higher frequencies suppressed viscoelastic deformation, reduced hysteretic energy dissipation, and shifted failure morphology from matrix-dominated cracking to fiber breakage. Constant amplitude tests at 60% (Formula presented.) confirmed these trends, with specimens failing at 5 Hz but surviving 3 million cycles at 20 Hz. Across all frequencies, FFE remained consistent (0.096 (Formula presented.) 0.0144 kJ/m (Formula presented.) K), supporting its role as a rate-independent scalar indicator of fatigue damage.

AB - This study investigates the influence of cyclic loading frequency on the fatigue limit of additively manufactured-compression molded (AM-CM) short carbon fiber thermoplastics (20 wt% CF-ABS). Accelerated fatigue characterization was performed using passive infrared thermography under a staircase loading protocol at 5, 10, 15, and 20 Hz. Displacement accumulation, stabilized surface temperature ((Formula presented.)), and fatigue fracture entropy (FFE) were jointly analyzed to capture frequency-dependent damage mechanisms. Results show a notable increase in fatigue limit from 52.14% (Formula presented.) at 5 Hz to 61.14% (Formula presented.) at 20 Hz. Higher frequencies suppressed viscoelastic deformation, reduced hysteretic energy dissipation, and shifted failure morphology from matrix-dominated cracking to fiber breakage. Constant amplitude tests at 60% (Formula presented.) confirmed these trends, with specimens failing at 5 Hz but surviving 3 million cycles at 20 Hz. Across all frequencies, FFE remained consistent (0.096 (Formula presented.) 0.0144 kJ/m (Formula presented.) K), supporting its role as a rate-independent scalar indicator of fatigue damage.

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On the Influence of Cyclic Loading Frequency on Fatigue Limit of Short-Fiber Thermoplastics

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