Search

Research Data for Long-term retainment of a foreign body in the esophagus in an adult: a case report by Yong Li, Rongguo Wang, Qing Feng, Sai Zhang, Ce Wang and Xiaofei Song in Journal of International Medical Research

In this study, graphene/MoS2 quantum dots (G/M QDs) hybrid nanostructures were synthesized in two steps. The bulk materials were separately converted into quantum dots by combining physical exfoliation and solvothermal treatments. Then, the two QDs were assembled together in a hot water bath. The products exhibit excellent fluorescence and gas sensitivity to NO2 and NH3, which can be manipulated by adjusting the proportion of the components. The light-reinforced effect on the gas sensing properties of quantum dots was verified by analysing the photothermal heating curves. Due to these properties, the developed hybrid QDs are potentially suitable for gas sensing applications.

In this paper, we study the mechanical behaviors of variable-stiffness composite laminates by setting curvilinear fiber paths. We assume that the fiber orientation angles vary linearly with the reference axis. Based on the different fiber paths, we vary the fiber placement formats and the curvilinear fiber orientation angles of the composite laminates, and then make the simulation for the buckling loads of the three kinds of laminates: the straight fiber placement, the curvilinear fiber placement and the mixed fiber placement. By comparing and analyzing, we give the best fiber placement format and the curvilinear fiber orientation angle. The study provides references to the design of variable-stiffness composite laminates.

The heated-mandrel winding method (HMWM) is a new technology. However, the trial-and-error method usually used is not universally adopted in the manufacturing process of shells that have different shapes and performance requirements. Determining the heating process for the HMWM based on theoretical analysis has become an immediate problem. In this paper, a numerical simulation program for the HMWM is developed using the finite element software ANSYS and the programming language APDL. The entire process, which starts with the winding process and ends with the complete curing, is numerically simulated. The temperature distribution and change law, curing degree, and reactive calorific intensity are analyzed. The relationship between the heating process and the outer surface temperature changes of the composite shell is derived based on the principle of temperature control in the HMWM. The heating process is optimized in accordance with the analysis, and the experimental results show that, based on the optimized heating process, the outer surface temperature range of the shell can be controlled during the winding process. Furthermore, the complex interactions among the temperature, curing degree, film coefficient, and heat transfer coefficient of the composite are investigated. This provides the basis for the technology optimization based on theoretical considerations.

We studied interfacial shear strength (IFSS) in carbon fiber (CF)-reinforced poly (phthalazinone ether ketone) (PPEK) composites system, with emphasis on the influence of forming temperature of composite and sizing agent on CFs. To obtain apparent IFSS of CF-reinforced PPEK composites shaped at various forming temperatures ranged from 20 up to 370 degrees C, microbond test was carried out at single-fiber composites. Results of microbond test showed that apparent IFSS was directly proportional to the difference between the matrix solidification temperature (forming temperature) and the test temperature and approximately 80% of the apparent IFSS in CF/PPEK composite system was attributed to residual radial compressive stress at the fiber/matrix interface. By sizing CF with sizing agent, the wettability of the fiber by the matrix was improved and the final apparent IFSS was also improved. POLYM. COMPOS., 34:1921-1926, 2013. (c) 2013 Society of Plastics Engineers

Self-healing materials are inspired by biological systems in which damage triggers an autonomic healing response. Epoxy resin-based self-healing system was demonstrated using tungsten (VI) chloride catalyst with a co-activator (phenylacetylene) that initiates ring-opening metathesis polymerization of dicyclopentadiene. The microcapsules with diameter of 200 ± 40 µm and average wall thickness of 5 µm were synthesized. Crack trigger process was analyzed by using finite element methods, the results indicated that the crack will be attracted toward the microcapsules when the wall thickness of microcapsules is in the range of 5–20 µm. The mechanism of tungsten (VI) chloride catalyze polymerization was studied. Environmental stability of tungsten (VI) chloride was investigated. Self-activated and self-healing samples were prepared and the healing efficiency was evaluated. It was found the concentration of catalyst have a significant impact on the virgin properties of the composites and the healing efficiency. The highest healing efficiency 64.9% was obtained with 15 wt% catalyst at self-activated samples. In the case of 10 wt% tungsten (VI) chloride and 10 wt% microcapsules, in situ self-healing sample yielded a healing efficiency of approximately 38.0%.

The finite element method is used to study delamination problem of composite hull structure. Stress analysis and delamination analysis of the hull are based on laminated plate theory and exponential forms of cohesive models respectively. By using commercial finite element software ANSYS, a two-dimensional model of the hull structure is established. Interface element based on cohesive model is inserted into potential delamination field and contact element is used in the model to avoid adjacent mesh embedded, and slamming loads is imposed as a bending moment in structure stress analysis. The calculated results show that this method can be well predicted delamination initiation and growth of the hull. Under a certain given slamming bending loads, delamination first occurs near middle layer of the hull structure, and delamination location in the vicinity of the stiffeners. The results may provide favorable references to prevent delamination of composite hull in the structure work.

In this paper, we study the problem of effective engineering elastic constants of stator core lamination of water turbogenerator. The three-dimensional transformations of elastic constants of composite lamina between the principal material coordinate system and the reference coordinate system are given, then the stator core lamination is modeled as the composite laminate and by utilizing the thick laminated plate model, we determine effective engineering elastic constants of the stator core lamination. Finally, a simple example is included to demonstrate the validity of the model and the programme codes.

The macro-properties of CF/PPEK and CF/PPES, which are two kinds of high performance thermoplastic composites, depend greatly on their interfacial structures. In this paper interfacial morphological structures of the two composites were investigated and analyzed by X-ray photoelectron spectroscopy (XPS). The results revealed that some new functional groups were generated that promoted strong physical and chemical interactions on the interface between fiber and matrix of CF/PPEK and CF/PPES composites. High temperature bending properties were tested and analyzed, and the changes in high temperature mechanical properties and retention rates were followed. A T r –n model was used to predicted the high temperature mechanical properties of CF/PPEK and CF/PPES composites. The results were consistent with the test results, which verified the feasibility of the T r –n model.