Wenbo Liu

Surface Modification of Poly(urea-formaldehyde) Microcapsules and the Effect on the Epoxy Composites Performance

The surfaces of poly(urea-formaldehyde) (PUF) were modified by γ -glycidoxypropyltrimethoxy silane (KH560) in order to improve the interfacial bonding between self-healing PUF microcapsules and epoxy matrix. The modification mechanism between PUF microcapsules and KH560 was studied. X-ray photoelectron spectra (XPS) analyses showed that the silane coupling agent molecular binds strongly to the surfaces of PUF microcapsules. Chemical bond (Si–O–C) and hydrogen bond were formed at interface by the reaction between Si–OH and the hydroxyl group of PUF microcapsules surface. The tensile and impact resistance tests revealed that strength and toughness of the composites was improved significantly. Furthermore, scanning electronic microscopy (SEM) photographs of the fractured surface confirmed that the silane coupling agent plays an important role in improving the interfacial performance between microcapsules and resin matrix.

Effect of Arc Spraying Power on the Microstructure and Mechanical Properties of Pb-Sn Coating Deposited onto Carbon Fiber Reinforced Epoxy Composites

In this study, Pb-Sn coatings were deposited on carbon fiber reinforced epoxy composites (CFRE composites) by means of plasma spraying as a permeation barrier in the applications of composite pressure vessels. The bonding strength of the Pb-Sn coatings-substrates with different plasma spraying power was tested on a RGD-5 tensile testing machine. The microstructures of the as-sprayed coatings have been examined by scanning electron microscopy (SEM), respectively. The result showed that the melting extent and the bond strength of the coatings were evidently improved with the increasing of spraying power. Observation of fracture surfaces shows that carbon fiber bundles can bond well with Pb-Sn coatings using 42 kW spraying power.