It is known that for creating advanced polyole n/ cement-based composites the polymer surface should be converted into a layer which is compatible with the inorganic component. In this respect, plasma chemistry offers additional solutions to the wet chemistry approach. It has been demonstrated during the last decade that cold plasma-mediated reactions are suitable for etching and surface functionalizing even the most inert polymeric substrates, including Te on, polypropylene (PP), and polyethylene (PE). In this paper composite preparations from SiCl 4 -cold plasma and chromic acid-treated brillated PP substrates and cement are described. The nature of plasma-and wet chemistry-induced surface functionalization and etching processes was monitored using survey and high-resolution X-ray photoelectron spectroscopy (XPS), attenuated total re ectance Fourier transform infrared (ATR-FTIR) spectroscopy, atomic force microscopy (AFM), and dynamic water contact angle measurements. It has been demonstrated that the plasma-exposed surfaces result in increased adhesion between the bers and the cementitious matrix in comparison with the chromic acid-modi ed bers. It has been shown that the improved tensile strength values can be related to the treatment-generated polar surface functionalities as well as roughness.
In this paper, to determine the dynamic strength model for steels, a new approach which does not rely on the Hopkinson bar test has been proposed. As the DH36 steel for example, using the results of Taylor impact test and the quasi-static compression test, the initial parameters of Johnson-Cook plastic strength model have been fitted out, then the initial strength parameters have been optimized using the optimization techniques of the sparse Taylor impact cylinder. It has been shown that the optimized results in numerical simulation are consistent with results of Taylor impact test, and the optimized Johnson-Cook model can also well describe flow stress curve fitted from the Hopkinson bar test.
The mechanical behavior of two composites, i.e., CF3031/QY8911 (CQ, hereafter in this paper) and EW100A/BA9916 (EB, hereafter in this paper), under dynamic loadings were carefully studied by using split Hopkinson pressure bar (SHPB) system. The results show that compressive strength of CQ increases with increasing strain-rates, while for EB the compressive strength at strain-rate 1500/s is lower then that at 800/s or 400/s. More interestingly, most of the stress strain curves of both of the two composites are not monotonous but exhibit double-peak shape. To identify this unusual phenominon, a high speed photographic system is introduced. The deformation as well as fracture characteristics of the composites under dynamic loadings were captured. The photoes indicate that two different failure mechanisms work during dynamic fracture process. The first one is axial splitting between the fiber and the matrix and the second one is overall shear. The interficial strength between the fiber and matrix, which is also strain rate dependent, determines the fracture modes and the shape of the stress/strain curves.
In this paper, dynamic mechanical property tests under different tempreture and strain rate of high strength steel 18NiC250 are conducted by means of Hopkinson pressure bar technique. The results of tests show 18NiC250 steel is not only very sensitive on strain rate, but also sensitive to temperature. The rate relative constitutive model of this steel is obtained and well predicts dynamic mechanical property after yielded.
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