Functional interlayers in multiphase materials

Properties of a three-dimensional interlayer formed between the reinforcement (fiber) and the matrix are final properties of composite materials. It means that surface properties, chemistry of the coated fiber and the matrix play a very important role for achieving good adhesion (a primary factor for stress transfer from the matrix to the fiber) and strong bonding between the fiber and the matrix (to gain the best possible composite mechanical properties). The aim of this work was to prepare thin films with siloxane structure by glow discharge polymerization technique, and the film serves in the end as an adhesion interlayer between the glass fiber and the polyester resin. Plasma polymerized dichloro(methyl)phenylsilane, hexamethyldisiloxane and vinyltriethoxysilane thin films were deposited on the surface of glass slides, silicon wafers and glass fibers. Chemical composition of the plasma polymers on planar substrates was examined by Fourier transform infrared and X-ray photoelectron spectroscopies, surface morphology was studied by atomic force microscopy and surface properties were evaluated by contact angle measurements as the free surface energy. Adhesion between the plasma polymerized film and the glass slide was tested using fully PC-controlled scratch tester with the Rockwell diamond tip. Performance of glass fiber/polyester composite was assessed using a short beam shear and the test revealed that the plasma-polymerized vinyltriethoxysilane interlayer was the best and the interlaminar shear strength was 75% higher than that for untreated fibers.