STOCHASTIC ANALYSIS OF THE INTERPHASE THICKNESS AND MODULUS IN CARBON FIBER REINFORCED POLYMER MATRIX COMPOSITES

Atomic Force Microscopy based Peak Force Quantitative Nanomechanics Mapping (PFQNM) technique with the high lateral resolution was used for the characterization of the interphase in polymer matrix composites (PMC) at the nanoscale. Details of the calibration parameters include probe stiffness, real spring constant, tip radius, tapping force, deformation level, synchronous distance, drive3 amplitude sensitivity (DDS3), and deflection sensitivity for heterogeneous PMC, were discussed. Reduced modulus, adhesion, and deformation results were used to examine the interphase zone thickness and properties. The symmetric composite laminate plates have a thickness of similar to 8mm. Specimens from the subsurface (similar to 400 mu m from the surface) and the depth (similar to 4mm from the surface) were considered. The polymer matrix composite samples have been exposed to heat and humidity. AFM Multimode 8, scanner type J with a maximum scanning window of 125 mu m x 125 mu m, was used. The Derjaguin, Muller, Toropov (DMT) equation was applied to the retract curve to calculate the elastic modulus. The Weibull model was used to examine material properties' statistical distribution. The scale parameter and the Weibull modulus (shape parameter) of the distribution characterize the data's scattering. A higher Weibull modulus means a steeper function and a lower dispersion. The Weibull analysis results illustrated the effects of the local moisture content on the interphase thickness and the reduced modulus.