Nanoscale Stress Distribution in Silica-Nanoparticle-Filled Rubber as Observed by Transmission Electron Microscopy: Implications for Tire Application

Abstract

Nanoparticle-filled rubber under tensile deformation was observed in situ by transmission electron microscopy (TEM), and the spatial distributions of the local maximum and minimum principal strains (ε max and ε min ) under tensile deformation were determined experimentally for the first time. The local ε max showed that deformation behavior depends heavily on the local structures and their spatial arrangements. Additionally, greatly deformed rubbery regions were found to appear along a network consisting of silica aggregates (silica-aggregate network). The distribution of the local ε min revealed the reorganization mechanisms of the internal hierarchical structures. The finite element method (FEM) was then applied to a series of TEM images under tensile deformation to simulate the structural changes, principal strains, and von Mises stress. The simulated morphology and ε max were in excellent agreement with the experimentally obtained morphology and strain. The distribution of the simulated von Mises stress, obtainable only from the FEM based on the experimental results, revealed that large stress propagates along the silica-aggregate network parallel to the tensile direction, suggesting that the silica-aggregate network may be primarily responsible for providing mechanical strength to the nanoparticle-filled rubber under deformation. Since the stress concentrates along the silica-aggregate networks, cavities appeared along these "stress pathways." The present study would pave the way to understanding the microscopic factors determining the macroscopic mechanical properties of rubber nanocomposites mainly used for automobile tires and seismic isolation rubber.

In situ transmission electron microscopy observation of the deformation and fracture processes of an epoxy/silica nanocomposite

“…Herein, we used in situ transmission electron microscopy (TEM) to study the deformation and fracture processes of a glassy epoxy film containing independently dispersed silica nanoparticles during the stretching process. 20–22 We first confirmed the wide area of deformation for the epoxy nanocomposite film in which a crack propagated. This enabled us to evaluate (1) how a silica nanoparticle affected crack propagation and (2) how a nanovoid was formed in close proximity to the epoxy/silica interface.…”

Analysis on Microstructure–Property Linkages of Filled Rubber Using Machine Learning and Molecular Dynamics Simulations

“…This means that the i-th and j-th loops in Figure 16 represent different aggregates, although they were connected physically with the filler particles surrounded by the orange circles. On the other hand, it was reported in some studies that the stress induced in the rubber region between the filler aggregates that were considerably deformed during the deformation process was the main source of stress in the entire system [ 12 , 25 , 63 ]. This conclusion implies that the distribution of filler aggregates may be a key factor affecting the mechanical properties of filled rubber.…”

“…In addition, the difference between the distributions of the filler aggregates in the positive and negative examples extracted by the CNN was investigated because the CNN-extracted aggregate was a subset of the PH-extracted aggregate and could be considered a core structure, as described above, and some studies reported that the filler aggregate distribution was a factor determining the mechanical property [ 2 , 3 , 12 ]. The positions of the filler aggregates extracted by the CNN represented by the coordinates of the pixels with positive values were analyzed by the PH.…”

“…Filled rubber is a composite material fabricated from polymers and fine filler nanoparticles, and its mechanical properties are directly related to tire performance, such as rolling resistance, abrasion resistance, and wet traction [ 1 , 2 , 3 , 4 ]. To establish a relationship between the mechanical properties of the rubber and filler morphology, X-ray scattering, electronic microscopy, and atomic force microscopy studies were conducted [ 3 , 5 , 6 , 7 , 8 , 9 , 10 , 11 , 12 , 13 , 14 ]. However, these techniques could only infer their mechanical properties from the observed differences between the microstructures in the sample.…”

Covalently integrated silica nanoparticles in poly(ethylene glycol)-based acrylate resins: thermomechanical, swelling, and morphological behavior

“…29,36,37 Several studies have investigated the influence of silica nanoadditives on the composite properties for use in applications such as automobile tires, electrical products, and coatings. [38][39][40][41][42][43] Dizon et al analyzed the thermomechanical properties of 3D-printed nanocomposites to be used as biomedical and microfluidic devices and discovered that increasing the loading of silica nanoparticles lead to higher stiffness. 32 Earlier work from our laboratory noted that nanocomposites containing unfunctionalized SiO 2 nanoparticles exhibited the behavior that the addition of particles caused the composite's Young's modulus and ultimate compressive stress to increase by 2Â and 3Â, respectively.…”