In Situ Nanostress Visualization Method to Reveal the Micromechanical Mechanism of Nanocomposites by Atomic Force Microscopy

Abstract

An in situ atomic force microscopy (AFM) nanomechanical technique was used to directly visualize the micromechanical behaviors of polymer nanocomposites during compressive strain. We obtained a stress distribution image of carbon black (CB)-filled rubber at the nanoscale for the first time, and we traced the microscopic deformation behaviors of CB particles. Through this experiment, we directly revealed the microscopic reinforcement mechanisms of rubber composites. We found that CB-filled rubbers exhibited heterogeneous local microscopic deformations, which were related to the dispersion of CB particles in rubber matrices. The local stress distributions of the rubber composites showed heterogeneity, and the stresses were concentrated in the regions near the CB particles during compression. The area of stress concentration gradually expanded with increasing strain and eventually formed a stress network structure. This stress network bore most of the macroscopic stress and was considered the key reinforcement mechanism of CB-filled rubber. The stress transfer process in the rubber matrix was visualized in real space for the first time. Based on the image data from the AFM experiments, we used finite-element method (FEM) simulations to reproduce the microscopic deformation process of CB-filled rubber. The stress distribution images simulated by FEM showed heterogeneity consistent with AFM. In this study, an in situ visualization of material deformation confirmed the predictions of microscopic deformation behavior from previous theories and models; it also provided new insights into the microscopic reinforcement mechanisms of CB-filled rubber composites based on microscopic stress distribution images.

Performance Enhancement of Silicone Rubber Using Superhydrophobic Silica Aerogel with Robust Nanonetwork Structure and Outstanding Interfacial Effect

“…Also, the XLD is well correlated in tensile strength, which can be used to indicate partly the mechanical property of rubber nanocomposites. Moreover, the filler–rubber interfacial interaction (bound rubber) is crucial to the properties of the rubber nanocomposites. , …”

“…Moreover, the filler−rubber interfacial interaction (bound rubber) is crucial to the properties of the rubber nanocomposites. 38,39 For quantitative analysis of the bound rubber in composites, all extracted solids were thermogravimetrically analyzed to quantitatively determine the bound rubber (Figure S11). The bound rubber can be quantified through the mass ratio of unextractable PVMQ to silica (R BR ) and the mass percentage of unextractable PVMQ to the original PVMQ matrix (P BR ) (Figure 5b,c).…”

Simultaneous Visualization of Microscopic Conductivity and Deformation in Conductive Elastomers

“…In our recent work, we developed a novel approach based on nanomechanical AFM to successfully track the microscopic deformation and stress distribution of nanocomposite materials in situ. 38 This unique approach will make it possible for us to simultaneously track the mechanical response and the electrical response of a material during deformation at the nanoscale. In this work, we introduce a novel method combining in situ deformation, nanomechanical AFM and C-AFM, successfully characterizing the microscopic deformation and conductivity of conductive elastomer composites of carbon black (CB)/isoprene rubber (IR) and carbon nanotubes (CNTs)/hydrogenated nitrile rubber (HNBR).…”

Simultaneous Visualization of Microscopic Conductivity and Deformation in Conductive Elastomers

“…AFM can measure the microscopic mechanical properties of a sample by pressing a nanoprobe against the material’s surface, which is known as the nanomechanical AFM technique. − Furthermore, the conductive AFM (C-AFM) mode allows visualization of the microscopic electrical properties of the sample surface by forming a conductive loop between the probe and the sample. − This feature of multiple functional characterizations gives AFM the potential to be an important tool for studying the microscopic mechanisms of conducting elastomers. In our recent work, we developed an approach based on nanomechanical AFM to successfully track the microscopic deformation and stress distribution of nanocomposite materials in situ . This approach will make it possible for us to simultaneously track the mechanical response and electrical response of a material during deformation at the nanoscale.…”

“…In our recent work, we developed an approach based on nanomechanical AFM to successfully track the microscopic deformation and stress distribution of nanocomposite materials in situ. 43 This approach will make it possible for us to simultaneously track the mechanical response and electrical response of a material during deformation at the nanoscale. In this work, we introduce a method combining in situ deformation, nanomechanical AFM and C-AFM, successfully characterizing the microscopic deformation and conductivity of conductive elastomer composites of carbon black (CB)/isoprene rubber (IR) and carbon nanotubes (CNTs)/hydrogenated nitrile rubber (HNBR).…”