Optimizing fatigue performance of nacre-mimetic PE/TiO 2 nanolayered composites by tailoring thickness ratio
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ng-Yuan Wan and Guang-Ping Zhangb) Shenyang National Laboratory for Materials Science, Institute of Metal Research, Chinese Academy of Sciences, Shenyang 110016, People’s Republic of China (Received 22 February 2018; accepted 18 April 2018)
Nacre-mimetic (PE/TiO2)4 nanolayered composites (NLCs) with the nanocrystalline TiO2 layer thickness less than 30 nm and different thickness ratios of inorganic/organic layers were successfully prepared by using layer-by-layer self-assembly and chemical bath deposition method. Mechanical properties, especially fatigue properties of the NLCs with different thickness ratios were evaluated. The elastic modulus, hardness and fracture toughness, strain amplitude to fatigue limits of the NLCs reached 27.78 6 5.69 GPa, 1.33 6 0.31 GPa, and 4.16 6 0.20 MPa m1/2, respectively. Fatigue performance of the NLCs in the high and low cycle fatigue regimes was optimized by tailoring the thickness ratio of the TiO2/PE layers. The PE/TiO2 NLCs with the larger thickness ratio of ;3 has the high fatigue limit (the critical strain amplitude of 0.0853%) in the high-cycle fatigue regime, while that with the smaller thickness ratio of ;1 and ;0.5 are of the good fatigue strength in the low-cycle fatigue regime. The basic mechanism for the enhanced fatigue performance is elucidated.
I. INTRODUCTION
Due to the superior combination of strength and toughness, some natural biomaterials like seashells have drawn strong interest of many researchers in the recent years. The ratio for different architectures of shells is different. For instance, the microarchitecture of the shell of Pectinidae is ordered at three size scales, with a fourth level of organization existing in the three distinct layers across the shell thickness.1 While, nacre, an attractive biomaterial for its excellent hierarchical “mud-brick” structure, is composed of multiscale inorganic mineral platelets and organic protein biopolymers.2 Remarkable mechanical properties may result from higher strength provided by the hard inorganic component and good toughness contributed by the soft organic component. Furthermore, the mechanical properties of nacre are enhanced by crack deflection caused by inorganic platelet sliding, intergranular crack propagation manner when the crack invades the inorganic platelet, organic viscoplastic energy dissipation at the interface, bridge bonding between adjacent mineral platelets, progressive locking generated by nanoasperities on the aragonite tablets, nanoparticle rotation mediated by the nanoparticle–biopolymer Address all correspondence to these authors. a) e-mail: [email protected] b) e-mail: [email protected] DOI: 10.1557/jmr.2018.134
architecture, and the partial dislocation and the deformation twinning within the nanoparticles.3–9 In recent years, the investigations on the fabrication and mechanical properties of various nacre-mimetic materials, especially ceramic/polymer configuration: Al2O3/chitosan,10 Al2O3/ cyanate ester,11 calcium phosphate microplateles/sodium alginate,12 hydroxyapatite scaffolds
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