Interfacial phenomena, adhesion and macroscopic properties in polymer composites

The microfragmentation or the single-fiber composite method for the evaluation of,fiber-matrix adhesion in polymer composites is presented emphasizing advantages and drawbacks. The improvements of the methods introduced in recent years (laser Raman spectroscopy, optical examination of interfacial region, estimation of the stress state at the interface, consideration of viscoelastic properties of the matrix) to obtain more detailed information on the interface failure mechanisms are described. A modified method with a coaxial geometry, which extends the applicability of the test to brittle matrices, is shown. A number of experimental results obtained both with thermoplastic and thermoset matrices containing carbon and glass fibers is reported. Chemical modifications of carbon fiber surfaces were carried out, which effectively changed the adhesion to the high-performance bismaleimide matrix. In particular, the treatment with ammonia is shown to be promising for improvement of adhesion in graphite/bismaleimide composites.