Functional interlayers in multiphase materials

journal article - other

English

Multiphase materials, e.g. composites, combine materials of distinct physical and chemical properties. The type of adhesion bonding gives characteristics of the interface between two phases in contact. Strong bonding is often demanded for multiphase materials under loading. However, a strong interfacial bonding increases the strength of multiphase material at the expense of the material toughness. A functional interlayer deposited between two phases can eliminate this conflict of material parameters. A proper thin film with adhesive bonding to both the phases results in an improvement of the material strength and toughness simultaneously [1]. Functional interlayers are successfully used in fiber-reinforced composites, where the interlayer has to enable the stress transfer from the matrix to the fiber. There is a schematic illustration of composite cross-section together with a detail of composite interphase in Figure. The interphase is an intermediate region between the fiber and the matrix and it comprises the interlayer and a part of the matrix affected by the presence of the coated fiber. Glass fibers, used as reinforcements for thermosetting resins, are coated by silane coupling agents using the wet-chemical process. However, these commercially prepared interlayers are not fully functional [2]. Plasma polymer films deposited from organosilicon monomers are potentially applicable as effective functional interlayers for glass fiber/polymer composites [3]. We have developed a new RF helical coupling system for the plasma-polymer deposition on flat substrate, single filament and continuously rewinding bundle of fibers. Selected organosilicon monomers (hexamethyldisiloxane, dichloro (methyl) phenylsilane, vinyltri-ethoxysilane, tetravinylsilane) were tested for preparation of functional interlayer using continuous and pulsed plasma. The adhesive bonding at the glass/interlayer interface was characterized using a scratch test together with optical microscopy. Our results revealed that the critical load could be higher by one order than that one for an interlayer prepared by the wet-chemical process. Chemical composition and structure of deposited plasma polymers were analyzed by infrared and X-ray photoelectron spectroscopies using the depth profiling. Scanning electron and atomic force microscopies enabled to determine the film surface morphology, which is very important factor for strong bonding at the interlayer/matrix interface. Functional species at the film surface were checked by photoelectron spectroscopy. Functional interlayers deposited on glass fibers were tested in a form of model composites with respect to the interfacial shear strength (microbond test) and the interfacial toughness (fragmentation test). Our results on functional interlayers stimulate researchers to continue in their effort to form controlled interphases.

[B] Fourier transform infrared spectroscopy, Photoelectron spectroscopy, Atomic force microscopy (AFM), Scratch test; [C] PACVD; [X] Plasma polymer

PŘIKRYL, R.; ČECH, V.; BÁLKOVÁ, R.; VANĚK, J.

2003

1. 1. 2003

0257-8972

Surface and Coatings Technology

173-174

173-174

Swiss Confederation

858

863

5