Session: 04-15-01: Nanoengineered, Nano Modified, Hierarchical, Multi-Scale Materials and Structures

Paper Number: 144462

144462 - Deconvolution of Atomic Force Microscopy Data From the Effects of Destructive Indentation and Rigid Body Motion of Embedded Particles in Heterogeneous Systems 

Atomic force microscopy (AFM) is a crucial tool for nanoscale material characterization of soft materials including polymers. However, AFM data is easily convoluted by a multitude of real, non-ideal artifacts. Some of them have been identified by researchers and techniques have been developed to deconvolute AFM data and validate its reliability. Yet, several effects remain poorly understood. Two of these effects have been identified as destructive AFM indentation or matrix damage and rigid body motion undergone by hard particles embedded in a polymer matrix under an indentation load. Finite element analysis (FEA) and AFM are used to study the effects of these mechanisms on AFM data. Simulated and experimental data are combined to develop a correction technique to deconvolute AFM data, adding to the available methods AFM scientists have at their disposal.

In particle-matrix composites, varying degrees of stiffness across the sample make non-destructive AFM indentation challenging. While previous work has been done to examine nanoscale damage from various exogenous sources, and techniques have been developed to prevent destructive AFM, little if any investigation has been done into how to proceed with AFM experimentation after destructive indentation has already occurred. Research has also been done on characterizing the nature of the interphase region in nanocomposites using AFM experiments and FEA by simulating polymer models with large particle and interphase regions. However, the effect of rigid body motion undergone by these particle inclusions under load, which will occur for particles of both realistic densities and similar size to that of the AFM probe tip, has been seldom investigated.

This paper studies the effects of matrix damage caused by destructive indentation and rigid body motion undergone by hard particles as well as their combined effect on AFM sensed data through the analysis of several finite element geometries. A soft polymer matrix and spherical AFM probe are modeled, and indentations are simulated with limited and enhanced displacement control loads ranging from 1 nm to 20 nm. The dimensions of the matrix are extensive enough that the effects of boundary conditions are insignificant. The Derjaguin-Mulle-Toporov (DMT) and Johnson-Kendall-Roberts (JKR) contact models are applied to probe-matrix interactions. Force-displacement curves are obtained and compared to calculate the reduced contact modulus for the healthy and damaged cases. A soft polymer matrix with hard particle inclusions is also simulated to determine the threshold force for rigid body motion and the effect of rigid body motion of particles on the force-displacement curve. The combined effects of plasticity and rigid body motion are simulated and the combined effects on the reduced contact modulus are studied.

Presenting Author: Maximillian Westby Arizona State University

Presenting Author Biography: Maximillian Westby is pursuing a bachelor's degree in mechanical engineering at Arizona State University with a focus on structural mechanics, advanced materials, material science, and finite element analysis. He plans to develop these interests through the pursuit of a master's degree and he is currently working toward publishing his first journal paper.

Authors:

Maximillian Westby Arizona State University
Masoud Yekani Fard California Polytechnic State University
Tyler Norkus Arizona State University
William Boutin Arizona State University