Polypopylene/nanoclay three-dimensional parts were produced without intermediate steps by direct injection molding to explore the influence of flow features and nanoclay incorporation in their impact performance. The nanocomposite was obtained by direct compounding of commercial PP with nanoclay masterbatch. The as-molded morphology was analyzed by X-ray and TEM analyses in terms of skin-core structure and nanoclay particle dispersion. The nanoclay particles induced the reduction of b-form spherulites, a known toughener. The impact behavior was assessed in tensile and biaxial modes. The PP nanocomposite molding toughness was practically unaffected by the processing melt temperature and flow rate. Conversely the nanoclay presence is influent in the impact performance. Under biaxial stress impact, the regions close to weld lines are tougher than the bulk and the fracture develops with main crack paths along the flow direction and the weld line. Cracking along the weld line results from less macromolecular interpenetration and chain entanglement, and unfavorable nanoparticle orientation. It seems that a failure mechanism which involves nanoclay delamination and multiple matrix crazing explains the toughening of PP in the directions where the nanoparticle orientation with respect to loading is adequate. POLYM. ENG. SCI., 53:724-733, 2013. FIG. 7. Depth sensing indentation results. (a) Typical indentation load-penetration depth curves for PP-6 sample in the skin and core. (b) Er and H profiles through the thickness for PP-6 sample. (c) Average values of Er as a function of MB content in the skin and core. (d) Average values of H as a function of MB content in the skin and core. [Color figure can be viewed in the online issue, which is available at wileyonlinelibrary.com.]
This article demonstrates the importance of stress concentrations on the life of industrial components. The design review and analysis of maintenance tasks (repair) can foresee and avoid such harmful design defects and/or bad habits that can reduce component life in service. Three steel shop examples are mentioned and details of these selected situations are analysed using metallurgy and finite element tools.
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