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Decoupling subsurface inhomogeneities: a 3D finite element approach for contact nanomechanical measurements



Veruska D. Malave, Edward Garboczi, Jason Killgore


Novel material properties can be attained when embedding three-dimensional (3-D) nanoparticles in a variety of polymeric matrices. These inhomogeneities influence the bulk mechanical response due to the local high modulus mismatch between the particles and the matrix. The degree of the mechanical mismatch that is seen near a composite surface depends on the geometry/shape and spatial location and orientation of the particle with respect to the external contact loading. Isolating each's particle contribution to the surrounding elastic fi eld can be numerically discerned but experimentally complex as there are limited direct characterization approaches available at the nanoscale. Atomic force microscopy (AFM) instrumentation is one such method that can quantify subsurface particle stiffness effects on nanocomposites with a resolution of a few nanometers. This work studies the spatial and geometrical effects of subsurface silver nanoparticles on the local composite stiffness of a polystyrene matrix using 3-D finite element (FE) models to interpret contact-resonance (CR) AFM measurements. The present FE-AFM fi ndings suggest both particle shape and particle orientation have a signi ficant role in the degree of uniformity of the stiffess distribution in the embedding matrix. The applied CR-AFM technique shows that the nanoparticle geometry can be clearly distinguished when such inhomogeneities are relatively close, 17 nm, to a free surface whereas material-interface measurements at deeper subsurfaces are obscured by experimental noise. This work demonstrates that (i) numerical solutions can assist in qualitatively elucidating nanoinstrumentation stiffness profi les in terms of particle shape and orientation and (ii) CR-AFM measurements can quantify the influence of particle geometry and orientation on the surface nanomechanics of nanocomposite materials.


Finite-element modeling, Atomic force microscopy, Nanoindentation, Nanoparticle geometry/orientation, Contact mechanics, Polymer-reinforced nanocomposites


Malave, V. , Garboczi, E. and Killgore, J. (2019), Decoupling subsurface inhomogeneities: a 3D finite element approach for contact nanomechanical measurements, Nanotechnology, [online], (Accessed July 15, 2024)


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Created April 23, 2019, Updated October 12, 2021