INVESTIGATION OF NANOMECHANICAL PROPERTIES AND INTERPHASE OF VARIABLESIZE HARD PARTICLES IN A SOFT MATRIX IN ATOMIC FORCE MICROSCOPY AND FINITE ELEMENT ANALYSIS

Hard particles suspended in a soft matrix significantly change the properties of the surrounding matrix via interactions with matrix and through the interphase that surrounds the particles, and atomic force microscopy ( AFM) is one of the techniques that has been used to characterize the nanoscale properties of such composites. AFM performed on particle-matrix composites results in complicated force-displacement data, and significant effort must be made to analyze that data. Finite element analysis (FEA) will be used in conjunction with experimental data to deconvolute and analyze the complex interactions between the AFM probe and particle-matrix composite. Previous work has been done to characterize both filled rubbers and biomaterials-which can be modeled with simpler particle-matrix composites-but the scenarios that were considered did not portray the full extent of the AFM probe's interactions with the hard particles or matrix. A neo-Hookean constitutive material relation is assigned to the soft matrix, and the Derjaguin-Muller-Toropov (DMT) and Johnson-Kendall-Roberts (JKR) contact mechanic models are considered during analysis of the probe-particle interactions. Data from AFM performed on hard carbon nanotube (CNT) particles embedded in thermoset epoxy resin will be collected to supplement and verify FEA. Simulated force-displacement and stress field data are analyzed to extract nanoscale mechanical properties and identify the key impacts different geometries have on collected AFM data.