Accelerated Zero-stress Hydrothermal Aging of Dry Glass, Basalt, and Carbon Fibers and  Service Life Prediction Using Arrhenius Model
Creators: Sunny, John
Publisher: name: University of Alberta Library
Year: 2023

<p>The utilization of fiber-reinforced polymer composites (FRPC) has rapidly increased over the past few <br>
decades because of their attractive mechanical properties, comparatively low volumetric mass density, and <br>
excellent corrosion resistance compared to traditional engineering materials like steel and aluminum. <br>
Exposure to moist and humid environments can accelerate the aging process of composite materials and <br>
negatively impact mechanical properties, thus shortening their service life. Environmental aging coupled <br>
with elevated temperature constitutes a severe case of accelerated aging. Notably, different composite <br>
constituents are impacted by environmental aging in different ways. As a result, it is crucial to comprehend<br>
for each constituent the kinetics and mechanisms of environmental aging to ensure the composite’s <br>
environmental durability. Data for service time assessments must currently be obtained via expensive and <br>
time-consuming test procedures.<br>
In recent years, thermoplastic matrix-based composites have been gaining popularity over their <br>
thermoset counterparts due to a practically infinite shelf life of raw materials, the ability to recycle <br>
thermoplastic polymers, and possible reductions in manufacturing cost that can be achieved using rapid and <br>
continuous fabrication processes. While thermosetting matrices typically offer excellent resistance to water, <br>
moisture exposure may significantly affect fibers embedded in thermoplastic polymers. Additionally, some <br>
structural applications use fibers devoid of any matrix (‘dry’ fibers), in which water exposure must be <br>
avoided. In both cases, moisture may significantly impact the reinforcing elements and the degradation rate.<br>
Comprehending the degradation of reinforcements is crucial for service applications involving dry and wet <br>
conditions, especially when prolonged contact with water above room temperature is present. Knowing and <br>
forecasting the extent of the material property deterioration in water is of great interest to designers and <br>
users of FRP structures. Environmental durability becomes a limiting factor in using composites for <br>
structural applications since the uncertainty of the material interaction with the environment compromises <br>
the superior material properties. The present work focused on the effects of hydrothermal aging on the <br>
mechanical durability of long glass, carbon, and basalt fibers by immersion in water at 60°C, 71°C, and <br>
82°C. Unidirectional thermoplastic composite tapes were also exposed to water at elevated temperatures to <br>
extend the study to composites. The main application of interest in the context of this research is <br>
thermoplastic composite piping where dry reinforcements or thermoplastic composite tapes are used as the <br>
load-carrying components. A service life forecast model was created for the fibers utilizing the Arrhenius <br>
technique. Using this modeling approach, it is possible to approximate the time it will take to attain a given <br>
degradation level over a specified range of temperatures. Scanning electron microscopy was used to <br>
evaluate morphology changes of fiber surfaces due to hydrothermal exposure. Fourier transforms infrared <br>
spectroscopy and mass dissolution studies were used to elucidate the mechanism of the strength loss.</p>