Collaborative Research: Damage Reversal in Composites — Elucidating the balance between Healability and Glass Transition Temperature

Due to their exceptional strength-to-weight ratios, fiber-reinforced plastics (FRPs) are increasingly used in high-performance applications such as aerospace, automotive, wind energy, sports equipment, and medical devices. However, they face challenges due to damage from repeated fatigue loading and poor recyclability. This can result in deficiencies in terms of performance, cost, safety, and reliability of structural components.

Existing approaches to improve fatigue life, such as adding nanomaterials or self-healing agents, provide limited benefits, as they cannot fully reverse accumulated damage. This research aims to overcome these challenges by developing a new class of FRPs based on vitrimers. Vitrimer polymers allow for the "reversal" of fatigue-induced damage when exposed to heat.

By exploring the balance between material stiffness, healability, and glass transition temperatures, the project seeks to develop vitrimers that not only enhance mechanical properties but also maintain the ability to heal repeatedly, significantly improving the durability, safety, and lifecycle of FRPs in demanding applications. The project will also develop interactive learning modules and mobile apps to teach students about the design of sustainable polymers and their applications.

Additionally, the project will involve outreach initiative for underrepresented groups, partnering with Montclair State University (a Hispanic Serving Institution), and engaging K-12 students through hands-on workshops and virtual demonstrations.

Vitrimers are polymers with associative dynamic covalent adaptive networks; these polymers have gained traction in the last decade, yet their potential for fatigue damage reversal remains largely unexplored. The researchers hypothesize that fatigue damage in vitrimers can be reversed by periodic heating above the topology freezing transition temperature (Tv) – at which rearrangement reactions occur.

Previous work on examining the mechanics of vitrimers has mainly focused on low glass transition temperature (Tg) variants; this compromises their creep resistance and limits their applicability in high-performance sectors. To address these challenges, this project will develop high Tg vitrimers using tri- and tetra-functional epoxides to enhance stiffness and creep resistance while maintaining reversible healing properties.

This project will systematically explore the “tug-of-war” between healability and Tg as a function of various parameters such as, polymer chemistry, catalyst type, and concentration, etc., thereby generating new fundamental knowledge. By combining reactive molecular dynamics simulations with experimental techniques, we aim to address three core scientific challenges: (1) understanding the trade-off between increasing Tg and maintaining healability, (2) elucidating the processing-structure-property relationships in high Tg vitrimers, particularly the influence of cross-linking density and molecular architecture on thermo-mechanical properties and healing efficiency, and (3) examining the impact of fiber reinforcement on the healing behavior of fiber-reinforced vitrimer composites, focusing on how the polymer-fiber interface responds to cyclic loading and periodic healing.

This research could transform the design of FRPs by enabling materials that not only resist but actively reverse fatigue damage, significantly enhancing durability, safety, and lifecycle performance across various industries while also promoting educational and diversity outreach.

This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.