Conductive composite of UHMWPE and CB as a dynamic contact analysis sensor

There has long been a need to experimentally measure the dynamic contact conditions of important engineering tribological systems, especially those with polymeric bearing surfaces that prove difficult to model. In order to experimentally quantify the dynamic contact conditions of geometrically complex polymeric bearing surfaces, a composite sensor material has been developed. In this study, qualitative morphological analysis of virgin ultrahigh molecular weight polyethylene (UHMWPE) and carbon black (CB) powders, as well as UHMWPE and CB powder mixtures of varying percentages was performed using field emission scanning electron microscopy (FESEM). Quantitative structure and friction analysis using atomic force microscopy (AFM) was performed on cryoultrasectioned block surfaces of compression-molded CB/UHMWPE composite. In addition, the mechanical properties of the composites were quantified using tensile testing, and the force dependence of the electrical properties was examined under dynamic compressive loading. The AFM results illustrated 5 mu m wide CB-containing channels enclosing 150 put diameter areas of UHMWPE within the CB/UHMWPE compression molded composite. Additionally, the dynamic coefficient of friction (Rho) of UHMWPE-dominant regions was 0.18, similar to that reported in the literature (0.2). A Student's t-test with 95% confidence level indicated no significant difference (p > 0.05) between the elastic modulus of 8 wt % CB/UHMWPE composite (208.9 +/- 11.1 MPa) and that of virgin UHMWPE control specimens (214.8 +/- 21.1 MPa) processed under the same experimental conditions. Measurement of the force-dependent nature of the electrical resistance of different CB wt % composites showed that the resistances decreased nearly two orders of magnitude when the compressive loads were increased from 0 to 5 kN. The structure, friction, mechanical, and electrical property results of this study collectively showed that a partially conductive, segregated network composite of nanometer size CB in UHMWPE was obtained without high-shear mixing, that has electrical properties allowing the material to be used as a dynamic contact sensor. (c) 2005 Elsevier Ltd. All rights reserved.