The influence of silane coupling agent composition on the surface characterization of fiber and on fiber-matrix interfacial shear strength

摘要

It is welk known that the fiber-matrix interface in many composites has a profound influence on composite performance.The objective of this study is to understand the influence of composition and concentration of coupling agent on interface strength by coating E-glass fibers with solutions containing a mixture of hydrolyzed propyl trimethoxysilane (PTMS)and gamma-aminopropyl trimethoxysilane (APS).The failure behavior and strength of hte fiber-matrix interface were assessed by the single-fiber fragmentation test (SEET),while the structure of silane coupling agent was studied in terms of its thickness by ellipsometry,its morphology by atomic force microscopy,its thickness by ellimpsometry,its morphology by atomic force microscopy,its chemicalo composition by diffuse reflectance infrared Fourier transform (DRIFT),and its wettability by contact angle measurement.Deposition of 4.5 x 10~-3 mol/L solution of coupling agent in water resulted in a heterogeneous surface with irregular morphology.The SFFT results suggest taht the amount of adhesion between the glass fiber and epoxy is dependent not only on the type of coupling agent but also on the composition of the counling agent mixture.As the concentration of APS in the mixture increased,the extent of interfacial bonding between the fiber and matrix increased and te mode of failure changed.For the APS coated glass epoxy system,matrix cracks were formed perpendicular to the fiber axis in addition to a sheath of debonded interface region along the fiber axis.