Session: 16-01-01: Government Agency Student Poster Competition

Paper Number: 150794

150794 - Multi-Scale Analysis of Enhanced Interfacial Shear Strength via Frontal Polymerization 

  Thermoset composites, renowned for their exceptional strength, lightweight nature, thermal stability, and chemical resistance, are extensively applied in the automotive and aerospace industries. Frontal polymerization (FP) is a superior alternative to manufacturing thermoset composites compared to conventional curing techniques like ovens or autoclaves due to its utilization of a self-propagating, highly exothermic reaction that accelerates production, saves energy, and lowers costs. However, the underlying mechanisms by which FP enhances performance remain unclear, and their potential has not been thoroughly explored, necessitating further in-depth research. It is well known that the adhesion between fibers and the matrix, i.e., the interphase, plays a crucial role in determining the load-carrying capacity and closely relates to the mechanical properties of the composite, apart from the inherent properties of the matrix and fibers. Thus, assessing the fiber-matrix interphase and identifying the predominant factors that contribute to the enhancement of composite material properties is imperative.

  Herein, we will first conduct the single fiber fragmentation test (SFFT) to determine the interfacial shear strength (IFSS) of carbon fiber-reinforced thermoset composites with three different resin matrices: epoxy resin, frontal resin, and hybrid resin. Furthermore, similar to how we evaluated tensile and bending properties, we will also analyze the impact of the weight content of the photo-initiator (PI) on IFSS. The purpose of these results is to illustrate the relationship between IFSS and mechanical parameters. Notably, one challenge in FP is the generation of bubbles from small-molecule volatilization, especially from gases produced during the initiator's decomposition. These bubbles lead to pores that can have a detrimental effect on composite performance. Therefore, we will intentionally introduce bubbles around the fiber monofilaments to create comparative specimens and assess the impact of bubbles on IFSS.

  To gain insight into the mechanisms behind the elevated IFSS, we will perform several analytical methods, including Fourier transform infrared spectroscopy (FTIR), X-ray photoelectron spectroscopy (XPS), atomic force microscopy (AFM), and scanning electron microscopy (SEM). FTIR will confirm the degree of resin curing, whereas XPS analysis will identify variations in the quantity of functional groups, specifically hydroxyl (-OH) and carboxyl (-COOH), within the interphase between carbon fiber and resin. Moreover, the AFM results will directly distinguish the interphase zones and provide measurements of the interface modulus.

  Additionally, we will focus on the distinct birefringence patterns exhibited by the three resin specimens, as well as disparate fracture modes as captured by SEM images. Typically, poor wettability and weak interfacial bonding diminish the mechanical properties of the composite, leading to premature carbon fiber fragmentation and interfacial damage. On the other hand, robust interfacial bonding will facilitate the release of energy through mechanisms such as breakage, pullout, and bridging, which improves the performance of the composites as a whole.

  The results and discussions aim to advance FP technique development, promote sustainable and rapid additive manufacturing or repair of thermoset composites, and create opportunities for large-scale industrial applications.

Presenting Author: Haining Zhang Syracuse University Composite Materials Lab

Presenting Author Biography: I received my Master's degree in Mechanical Engineering from Shanghai Jiao Tong University (China) in 2024 and my Bachelor's degree in Aircraft Propulsion from Xiamen University (China) in 2019. I joined Syracuse University Composite Materials Lab in May 2024. My research focuses on the design and advanced manufacturing of composites.

Authors:

Haining Zhang Syracuse University Composite Materials Lab
Amirreza Tarafdar Syracuse University Composite Materials Lab
Yeqing Wang Syracuse University Composite Materials Lab