Session: 03-04-01: Emerging Materials Technology

Paper Number: 121148

121148 - Rapid Welding of Fiber Reinforced Vitrimer Composites Using Ultrasonic Welding 

Healable polymers, particularly a new class called vitrimers, offer a potential solution to enhance the sustainability and longevity of polymers. Unlike traditional polymers like thermosets and thermoplastics, vitrimer polymers have a dynamic covalent adaptive network (CANs) that allows the fundamental building blocks of the chain to “unclick” and “re-click” by providing an external stimulus such as heat. This unclicking and reclicking is termed as rearrangement reaction. This rearrangement reaction usually takes minutes to hours to complete and achieve healing behavior in vitrimer polymers. We have made an exciting discovery that by using mechanical agitation, through ultrasonic horn, we can achieve this rearrangement reaction in a matter of miliseconds. In this presentation, we will demonstrate the weldability of both glass and carbon fiber-reinforced vitrimer composites through ultrasonication, yielding robust bonds. The core principle underpinning this process is the employment of ultrasonic vibrational energy as an initiator for bond exchange reactions. Lap shear tests performed on the welded specimens showed cohesive failure. The resulting weld joints for carbon fiber vitrimer composite showed a shear strength of 17.6 ± 2.1 MPa and shear modulus of 39.6 ± 1.6 MPa, while glass fiber vitrimer composite on the other hand, showed a shear strength of 10.8 ± 0.9 MPa and shear modulus of 19.4 ± 2.2 MPa. Since carbon fibers have higher thermal conductivity, they are able to dissipate the thermal energy generated by ultrasonication, resulting in better weld strengths.

Investigations were also carried out to understand the effect of catalyst concentration and repeatability of welds. Sufficient amount (5 mol%) of catalyst concentration is required for facilitating bond exchange reactions and to form a stronger bond. Higher concentrations, (10 mol%) of catalyst makes the polymer more viscoelastic and consequently leads to low bond strength whereas lower concentration of 2 mol% makes the material brittle leading it to behave like a thermoset with negligible dynamic bond exchange. For repeatability, five welds were performed on the same spot and the weld strength were found to be within the error limits. This investigation opens avenues for the swift and energy-efficient deployment of vitrimer composites across industrial domains, particularly in structural applications where ultrasonic welding can be used for assembling structures rapidly without the need to secondary bonding or specialized tooling.

Presenting Author: Ankush Nandi University of Washington, Seattle

Presenting Author Biography: I am a third year PhD student at the Mechanical Engineering department at the University of Washington, Seattle. My research area is focused on materials science, applied mechanics, high energy interaction of materials and automation.