Quantifying the Uniaxial High Cycle Fatigue Life of Laminated Composites with a Resonant Beam Test
Open Access
- Author:
- Kupchella, Chester Alan
- Graduate Program:
- Acoustics
- Degree:
- Master of Science
- Document Type:
- Master Thesis
- Date of Defense:
- December 06, 2016
- Committee Members:
- Robert Lee Campbell, Thesis Advisor/Co-Advisor
Stephen A Hambric, Committee Member
Kevin L Koudela, Committee Member - Keywords:
- FRP
Fatigue
High Frequency
Composites
Temperature Controlled
Viscoelasticity
Fiber Reinforced Polymer
Fiberglass
Vibration - Abstract:
- Fatigue characterization of glass fiber reinforced polymer (FRP) composites is a thoroughly researched topic, but no current methods achieve high predictive accuracy without significant experimental effort due to the added complexities of viscoelasticity and material inhomogeneity. This work aims to fill a gap in the literature by focusing on high-rate, high-cycle, fully-reversed axial fatigue of glass FRP composites. The experiment uses a structural resonance to impart a cyclic load at 22 Hz, 30 Hz, 55 Hz, and 110 Hz, which are higher frequencies than are typically used in fatigue measurements. Composite specimens are affixed to a beam driven near resonance, allowing many stress cycles to accumulate over a short period of time. Variable masses are attached to the beam ends to adjust the resonance frequency. The system resonance is a good measure of specimen modulus, which decreases as damage accumulates. Forced convective cooling controls specimen temperature effectively even at high frequencies. Each sample is fatigued to 10 million cycles and tested for residual strength. Residual strength and residual modulus correlate well regardless of loading frequency. Samples experienced a greater modulus and strength reduction when fatigued at 22 Hz than at higher frequencies tested herein. Residual strength and therefore predicted fatigue life both increase with loading frequency until 30 Hz. From 30-110 Hz there is no obvious trend in predicted fatigue life with loading frequency. More data should be collected in future work. However, these results suggest it may be possible to predict low-frequency fatigue from high-frequency tests as long as rate-dependent damage accumulation is well documented.