THE SCANNING FORCE MICROSCOPE AS A TOOL FOR THE DETECTION OF LOCAL MECHANICAL-PROPERTIES WITHIN THE INTERPHASE OF FIBER-REINFORCED POLYMERS

Scanning force microscopy (SFM) has been used to assess the local mech anical properties of fibre-reinforced polymers. Using a sinusoidal dis placement modulation (DM) and lock-in technique the method allows to c haracterize local viscoelastic properties with a high lateral resoluti on. The simultaneous measurement of the local electrical conductivity is proposed which facilitates the interpretation of the mechanical dat a. The investigation of cross-sections perpendicular to the axis of ca rbon fibres embedded in PPS delivers some information about the change in local stiffness within the interfacial region. As a first approach , assuming a single-exponential decrease in local stiffness along a ra dial line from fibre to polymer we find characteristic decay lengths w hich are distributed in a range between 20 and 80 nm. Further, a modif ied DM-mode is proposed which is expected to provide a contrast enhanc ement of the signal which is related to local stiffness. This can be a chieved by installing an additional feedback loop which keeps constant the amplitude of dynamic indentation (CDI-mode). (C) 1998 Elsevier Sc ience Ltd. All rights reserved.