Interphase characterization in polymer composites monitoring of interphasial behavior in dependence on the mode of loading

Single fiber model composites consisting of epoxy resin matrix and differen tly sized glass fibers were investigated using pull-out tests, scanning ele ctron microscopy (SEM), scanning force microscopy (SFM) and single fiber dy namic load test (SFDL). The inhomogeneous stress distribution along the emb edded fiber length could be visualized by monitoring. SEM images showed eit her cohesive fracture or adhesive failure on pulled-out fibers with differe nt sizings. The crack initiation and propagation were detected randomly and multiply distributed as the inhomogeneous interphase itself and depending strongly on the fiber-matrix model combination. The meniscus region acts as a material inhomogeneity and its appearence dep ends on the surface free energies of fiber and matrix and on the curing con ditions of the resin. SFM in force modulation mode has visualized different interphase thicknesses and gradients of local stiffness. The SFDL test has been shown as a worthful tool for the comprehensive determination of fiber -matrix interaction.