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The silo has the advantages of small area, good sealing conditions, low circulation costs, low cost and etc. It is currently the leading warehouse type of grain storage in China. Most silos still use gravity-based discharging methods, however, arches often form during silo discharging, it causes the pressure that should have been taken from the bottom of the warehouse to the wall of the warehouse. As a result, cracks may form in the silo walls causing serious damage. In addition, when there are workers above the grain surface or when the arch is manually broken, the collapse of the arch will not only result in personal injury or death of the grain surface staff, but also may damage the warehouse structure and facilities in the warehouse. In recent years, with the development of building technology, the silo volume has been continuously increasing, the diameter and height of the silo have also become larger and larger, and the related accidents caused by unloading and arching silos have also become more frequent Silo arch accidents in Daqing 2013, Lanxi 2015, in Heilongjiang province, and in Jing County in 2016 in Anhui province, for example, have resulted in the destruction of some silo facilities and casualties. Existing studies have shown that silo unloading and arching are closely related to the internal and external friction of grain. However, in those studies, a single circular particle is used in the current discrete element simulation. The real contact area of simulated grain is much smaller. As such, the simulation cannot objectively reflect the grain of the unloading process. The frictional situation is also more difficult to restore the mesoscopic dynamic process of unloading grain arching. In this paper, based on the existing PFC3D discrete element program, the micro particle simulation dust with larger viscosity coefficient was added to create an improved particle for the defect that the internal friction force of the circular particle in the discrete element simulation was smaller than that in the real grain. We used geometric methods in the structural mechanics model to determine the contact between the circular particles and derives the force-displacement relationship between the basic units. Based on typical accident cases and laboratory test results, the established particle structure mechanics model was used to simulate the force-displacement relationship between circular large particles and between small round particles and walls in the dynamic process of unloading grain and arching. The displacement map of shear stress and its stress characteristic curve were basically consistent with the experimental results. By using this model, the dynamic meso-mechanism of unloading and arching silos can be objectively reflected. The improved particle structure mechanics model proposed in this paper can not only be used to simulate the unloading and arching mechanism simulation, but also has certain reference value for the simulation of the characteristics of loose particles flow and the mechanism of the interaction between the bulk and the silo wall. [ABSTRACT FROM AUTHOR]

Graphene nanoplatelets (GNPs), the most important mass-produced graphene, are fabricated as a mechanical reinforcement for epoxy matrix nanocomposites. Current performance of GNPs as a reinforcing filler is limited by their agglomeration and weak interfacial interaction with certain polymer matrices. Herein, an approach to produce noncovalently functionalized GNPs (F-GNPs) is reported that can be extended to the industrial level of mass production. The one-step functionalization process uses melamine, a low-cost chemical, to improve the interfacial adhesion and dispersion in an epoxy matrix. The mechanical properties of nanocomposites prepared with the F-GNP flakes are much better (94.3% and 35.3% enhancements in Young's modulus and tensile strength, respectively) than those of the unfilled pure epoxy. Experimental data are analyzed using the Halpin-Tsai model. The fabrication process developed in this paper provides a strategy to use GNPs at the industrial level in lightweight and high-strength structural applications. [ABSTRACT FROM AUTHOR]

Polymer concrete (PC) has been widely used for quick repairing of concrete pavement and structures in recent years. This paper studies the mechanical behavior of the rubberized polymer concrete. Crumb and chipped rubber were used to replace fine and coarse aggregates in PC, respectively. A complete series of destructive tests including impact test, compression and splitting tensile tests and non-destructive methods including ultrasonic test, digital signal processing, electrical conductivity, and microstructure analysis was performed to demonstrate the various potential applications of the rubberized PC. X-ray diffraction (XRD) also provided information regarding the chemical composition and crystal structure of three different epoxy resin ratios. The results indicated that the rubberized PC reduced the workability and increased the porosity and air content of the mixture; however, reduced the cost and density, and improved ductility. Scanning electron microscope was used to analyze the interface between aggregates and adhesive materials. The correlation between the compressive strength and ultrasonic pulse velocity was determined and proposed for the rubberized PC. PC containing crumb rubber had a lower pulse velocity and higher damping properties than that of chipped rubber. Further, the Taguchi method was used to determine the optimum conditions for mechanical properties of the rubberized PC and ANOVA was then utilized to evaluate the level of influence and existence of interaction parameters. Based on this investigation, the rubberized PC can be an appropriate candidate for repair and rehabilitation applications. [ABSTRACT FROM AUTHOR]

Thermoplastic resin used as a matrix of fiber reinforced thermoplastics (FRTPs) is composed of high polymers that remain highly viscous even at a higher temperature than their melting points. As a result, they need a higher temperature, a higher pressure and longer process time to allow them to bond with fibers and consequently require large and specialized facilities. In this paper, a simple and fast fabrication method of vacuum assisted resin transfer molding (VARTM) method for hybrid fiber reinforced thermoplastic (HFRTP) was introduced. In order to fabricate HFRTP with the VARTM, glass and carbon fabrics were used as reinforcement and in-situ polymerizable epsilon caprolactam (ɛ-caprolactam) was used as the matrix. The obtained HFRTP had neither voids nor unfilled parts because the liquid state of ɛ-caprolactam was very low viscosity before polymerization. The fabrication method of the HFRTP proposed here showed a faster fabrication one compared with conventional fabrication methods. In order to apply this HFRTP to automotive structures, the performances of the HFRTP showed not only superior mechanical properties but also suitable for high-speed molding without expensive facilities, namely, within a few minute process time with a vacuum pump because they could be released from the mold without a cooling process. [ABSTRACT FROM AUTHOR]

In this paper, a novel computationally efficient multiscale framework based on the extended mechanics of structure genome (XMSG) is presented for predicting mechanical properties based on microstructure for Ti6Al4V parts fabricated by additive manufacturing (AM). The XMSG offers its novel capability to account for the effects of microstructure heterogeneity, porosity growth, and crack propagation for the multiscale calculations of the elastic/plastic/damage behavior of the AM parts in a computationally efficient manner. It is shown that XMSG can provide several orders of magnitude improvement in computational efficiency with the same level of accuracy compared to other conventional methods such as representative volume elements. The XMSG framework was applied to predict the tensile and compression behavior of AM Ti6Al4V, which showed very good agreement with the experimental results. In addition, the XMSG framework was able to predict the asymmetry in Young's modulus of the AM Ti6Al4V under tensile and compression loading as well as the anisotropy in the mechanical behavior under tension. • The proposed extended mechanics of structure genome is a novel computationally efficient multiscale homogenization method. • The method is used to successfully predict the mechanical behavior of additive manufactured Ti6Al4V with porosity. • The method is capable of predicting the anisotropy and asymmetry in the mechanical behaviors of Ti6Al4V. • The method is computationally superior to the existing homogenization method by more than two orders of magnitude. [ABSTRACT FROM AUTHOR]

• A nonlinear molecular structural mechanics model is proposed for microtubules (MTs). • Lattice defect in MTs can reduce both their Young's modulus and fracture strain. • Predictive equations are developed for MTs with different lattice defect levels. A nonlinear molecular structural mechanics (MSM) model is proposed in this paper for studying the tensile properties of microtubules (MTs). In the nonlinear MSM models, the interactions between tubulin monomers in MTs are treated as nonlinear axial and torsional springs, whose stiffness coefficients are extracted from all-atom molecular dynamics simulations. The Young's modulus and fracture properties of MTs under tension extracted from the present nonlinear MSM models are found to agree well with the existing simulation and experiment results, which shows the efficiency and accuracy of the proposed nonlinear MSM models. In addition, the nonlinear MSM models are also extended to investigate the tensile properties including Young's modulus and fracture strain of MTs possessing lattice defects. The results obtained from nonlinear MSM models are utilized to develop a predictive equation for quickly predicting the tensile properties of MTs with different lattice defect levels. [ABSTRACT FROM AUTHOR]