Effects of Different Surface Characteristics on the Fracto-Emission of Carbon Fiber Reinforced Composite Adhesive Bond Failures

The advent of fiber reinforced composite materials with superior properties over conventional metallic components have allowed rapid adaptation of these materials in a variety of industries. The aerospace, automobile, and marine industries have incorporated composite materials heavily into the vehicle structure, increasing the need to develop and investigate proper bonding and joining techniques. However, a proper understanding of such mechanisms with various surface characteristics is still under investigation. Fractures in structural components are accompanied by emission of electrons, positive and neutral ions, photons, and so on. Collectively these emissions are known as ‘fracto-emissions.’ This work focuses on utilizing fracto-emissions to improve understanding of bonding mechanisms. Carbon fiber composite samples with two different methods of surface preparation will be produced: roughening and chemical contamination. Prior to bonding, surfaces of these samples were characterized to determine surface free energy, surface roughness, and chemical profile. Following bonding, dielectric properties of the bonded specimens were collected. Bonded samples were then subjected to Mode I testing for fracture analysis, as well as the charges released by fracto-emission during bond failure were recorded using a mixed domain oscilloscope. An inverse relation between peak forces and dielectric relaxation strengths were observed. Strong correlations between the crack propagation and fracto-emission in terms of EM wave signal were observed.