Characterization of light weight composite proppants



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The research objectives are to develop experimental and computational techniques to characterize and to study the influence of polymer coating on the mechanical response of walnut shell particles to be used as proppants. E3-ESEM and Zeiss Axiophot LM are used to study the cellular microstructure and feasibility of polymer infiltration and uniform coating. Three main testing procedures; single particle compression, heating tests on coated and uncoated walnut shell particles and 3-point flexure tests are undertaken. In in-situ ESEM observations on both the coated and uncoated particles showed signs of charring at about 175 ? 200 ?C. Single particle compression test are conducted with random geometry particles and subsequently with four distinct shape categories to minimize the statistical scatter; flat top, round top, cone top, and high aspect ratio. Single particle tests on uniformly cut cuboid particles from walnut shell flakes are used to capture the nonlinear material response. Furthermore cyclic compression loads are imposed on flat top particles which reveal that significant permanent deformation set in even at low load levels. Computational models include Hertzian representation, 2D and 3D finite element models to simulate single coated and uncoated particles under compression. The elastic material with geometric nonlinear representation is not able to simulate the compression response observed during testing. The inelastic material representation is able to significantly improve the compression response and address the influence of geometric shape on particle response. A single uniform layer of polymer coat is introduced on the 3D models with nonlinear material definition. Coating provides a marginal improvement in load vs displacement response of the particles while increasing the ability of the particle to withstand higher loads.