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In this paper, we apply mesoscale numerical modeling to predict the effective elastic properties of conductive carbon-black/ultra-high-molecular-weight-polyethylene nanocomposites. The models are based on X-ray microcomputed tomography images. The images show that for the considered range of carbon additive weight fractions, the conductive carbon black (CB) particles are distributed around the ultra-high-molecular-weight-polyethylene (UHMWPE) granules forming a carbon-containing layer of a thickness on the order of 1-2 𝜇𝜇𝜇𝜇. Finite element models of representative volume elements (RVE), incorporating the CB-containing layer, are developed. The RVEs are generated based on the size and shape statistics extracted from processed microcomputed tomography images with further incorporation of the CB-containing layer by a custom image processing code. The layer is modeled analytically as a 2-phase composite consisting of spherical CB inclusions distributed in the UHMWPE matrix. Elastic moduli predicted in the models are compared to experimental data. Results show that the numerical simulations predict effective elastic moduli within the confidence intervals of the experimental measurements up to 7.5 wt % of CB inclusions. 

In this paper, we investigate ultra-high-molecular-weight-polyethylene (UHMWPE) doped with conductive carbon black (CCB) nanoparticles. This nanocomposite is considered a candidate for biomedical applications such as orthopedics. Micro-computed tomography (μCT) and scanning electron microscopy studies show that the composite has a complex microstructure consisting of larger particles of UHMWPE surrounded by a thin layer containing a high concentration of CCB nano inclusions. The overall mechanical properties of these composites depend on the volume fraction of CCB and the manufacturing procedures e.g., compression molding or equal channel angular extrusion. To predict the effective elastic properties of the CCB/UHMWPE nanocomposite, we propose a multiscale modeling framework based on a combined analytical-numerical approach. μCT images are processed to extract the size, shape, and orientation distributions of UHMWPE particles as well as the volume fractions and spatial distribution of CCB containing layer. These distributions are used to develop multiscale numerical models of the composite including finite element analysis of representative volume elements on the mesoscale, and micromechanical predictions of CCB containing layer on the microscale. The predictive ability of the models is confirmed by comparison with the experimental measurements obtained by dynamic mechanical analysis. 

Joint arthroplasty, specifically total knee arthroplasty (TKA) and total hip arthroplasty (THA), are two of the highest value surgical procedures. Over the last several decades, the materials utilized in these surgeries have improved and increased device longevity. However, with an increased incidence of TKA and THA surgeries in younger patients, it is crucial to make these materials more durable. The addition of nanoparticles is one technology that is being explored for this purpose. This review focuses on the addition of nanoparticles to the various parts of arthroplasty surgery comprising of the metallic, ceramic, or polyethylene components along with the bone cement used for fixation. Carbon additives proved to be the most widely studied, and could potentially reduce stress shielding, improve wear, and enhance the biocompatibility of arthroplasty implants. 

Ultra-High Molecular Weight Polyethylene (UHMWPE) is widely used as a bearing surface in total and partial joint arthroplasty. In addition to medical applications, this polymer is utilized in the fields of ballistic protection, sports, and industrial tribology. The addition of carbon allotropes, such as nanographite or carbon black powders, to UHMWPE offers potential benefits including added conductivity, increased wear resistance, and introduction of micro-tracers for understanding microstructural behavior and monitoring damage [1]. The mechanical properties of these Carbon/UHWPE nanocomposites can be enhanced by subjecting them to equal channel angular extrusion (ECAE) as a way to introduce large shear strains to achieve higher molecular entanglement of UHMWPE and better distribution of carbon nanoparticles [2, 3]. In this paper, micro-computed tomography (µCT) is used to characterize carbon black (CB) and nanographite (N27SG) reinforced UHMWPE polymers. It is shown that the procedure described in [1] results in almost uniform distribution of carbon inclusions around UHMWPE particles with both compression molding (CM), and ECAE processes. Multiscale numerical models of the composite are developed based on the µCT images, including mesoscale finite element (FE) models of representative volume element (RVE) on the mesoscale, and micromechanical predictions for carbon-rich interphase layers on the microscale.