Hygrothermal effect and statistical analysis of the interfacial performance of nano and microscale polymer composites

ABSTRACT

Hygrothermal exposure significantly impacts polymer composite (PMC) performance, affecting various industries. This study evaluated the short-term hygrothermal effects on PMCs by examining interfacial shear strength (IFSS), water uptake, glass transition temperature (Tg), and morphology. Data-driven techniques minimized experimental time while analyzing multiple factors. Specimens were immersed in water at 25°C and 70°C for 3, 7, and 14 days. The IFSS between carbon nanotube yarns and carbon fiber with epoxy (EPON™ 862) was measured before and after exposure. Statistical analysis indicated that fiber type significantly influenced IFSS, while time had a marginal effect and temperature had no impact. The IFSS decreased by 4.14% for CF/epoxy and 14.9% for CNT/epoxy. Water uptake analysis revealed weight gains of 0.465% and 1.566% for epoxy after 14 days at 25°C and 70°C, respectively. Morphological studies showed moisture penetration between 7 and 14 days. Thermomechanical analysis (TMA) indicated that pristine epoxy expanded by 0.318% of its original height. After 14 days, the Tg of epoxy decreased by 6.4% at 25°C and 9.7% at 70°C. Dynamic mechanical analysis (DMA) on dried epoxy samples showed similar Tg but varied tan delta curves due to plasticization. Short-term hygrothermal evaluation revealed degradation in interface quality and viscoelastic properties.

GRAPHICAL ABSTRACT

KEYWORDS:

• Carbon nanotubes
• carbon fibers
• interfacial shear strength
• hygrothermal
• polymer matrix composites

Acknowledgements

The authors want to thank Malik Lewis for SEM images, Cecil Evers for providing fixtures to cut specimens, Aspen Reyes for providing help with the TMA, Ivan Zheng for finishing preparing pull-out samples, Alex Hamberg for epoxy preparation and testing, and Trinity Francis and Alyssa Bauer for epoxy measurements.

Disclosure statement

No potential conflict of interest was reported by the author(s).

Author contributions statement

All authors contributed to the writing of the manuscript. Ana De Leon, Zipporah Harlan, and Rebekah Sweat devised the project, the main conceptual ideas, and the proof outline. Matthew Wadsworth and O. Arda Vanli developed the design of the experiments and analyzed the data using statistical programming. Okunzuwa Austine Ekuase and Tripp Lappalainen assisted with polymer weight and TMA measurements and performed their analyses. De Leon took the lead in writing the manuscript, performed the pull-out test measurements, and was in charge of the overall direction and planning. O. Arda Vanli and Rebekah Sweat helped supervise the project and the final version of the manuscript.