Key Engineering Materials Vols. 326-328

Abstract: This paper presents the results of an experimental study on the seismic performance of reinforced concrete (RC) bridge piers wrapped with FRP at the lap-spliced region. It is well known that the FRP wrapping on the surface of concrete bridge pier can prevent concrete cover from spalling and it can reduce the slip displacement of lap-spliced longitudinal re-bars due to confinement. In order to develop the effective way of strengthening the concrete bridge pier with poor lap-spliced longitudinal re-bars, which is not designed under seismic design consideration, a series of pier test under seismic loading condition is conducted. As a result, FRP wrapped bridge pier under seismic loading exhibits ductile behavior with plastic deformation at lap-spliced region. Half-scaled six circular and nine square pier specimens were tested under uniform concentric axial compression and quasi-static lateral loading at the top of the pier. For the purpose of comparison, two piers without lap-splice and two piers with lap-splice were not wrapped with FRP and tested under same loading condition. Other experimental parameters were the height of FRP wrapping and the reinforcing method. The experimental results showed that the FRP wrapping could significantly increase ductility of piers with lap-spliced longitudinal re-bars at the potential plastic hinge region.

Abstract: To quantitatively evaluate the mechanical effect of plants’ roots on slope reinforcement, this paper probes into the application of composite material theory and finite element method (FEM) to analysis of mechanical properties of soil and soil/root respectively. Soil with herbage roots is regarded as a kind of special composite material, soil is matrix and root is intensifier. Comparing to the test result, the result obtained by composite material model is not perfect but can be used to estimate the effect of roots on soil reinforcement. Moreover, the result obtained by FEM analysis confirms the effect of root on soil reinforcement, especially along the direction of root length.

Abstract: Microwave curing is a kind of technique that heat up the adhesive containing pole molecule by means of microwave and let it curing rapidly. The characteristic of microwave curing is discussed, and the technique and application of microwave curing are introduced.

Abstract: Since composite materials have high specific strength and stiffness, they are used for many fields such as aerospace and marine structures. According to such utilities, joining method between composites and metals must be developed. In this study, dimple treatment is carried out as a new reinforcing method for FRP/metal co-cured joint. Dimple treatment is applied to the adhesive surface of metal so that resin of FRP permeates into dimples and the strength of joints increases. It is revealed that dimple treatment achieves as high bonding strength as chemical surface treatment.

Abstract: The use of pultruded fiber reinforced polymeric (FRP) members in civil engineering applications can greatly reduce construction time and maintenance cost of structures, because pultruded members have high specific strength and excellent corrosion resistance compared to steel and concrete. Pultruded members for civil engineering application are mostly made of a polymeric resin system reinforced with E-glass fibers and, as a result, they have low elastic moduli. Therefore, stability is an important issue in the design of pultruded members. In this paper, the results of an experimental investigation into the global buckling behavior of pultruded thin-walled members subjected to axial compression are presented. The analytical solutions are validated through a comparison with the results of FE analysis as well as the experimental results.

Abstract: A simple and mass producible method was developed to incorporate multiwalled carbon nanotubes (MWCNTs) into electrospun silk fibroin (Bombyx mori) nanofibers. The process consists of dispersing the acid-treated MWCNTs in an aqueous silk fibroin solution, and blending this solution with a water-soluble polymer, poly(ethylene oxide) (PEO), followed by electrospinning of the composite solution. The morphology and microstructure of the electrospun nanofibers were characterized using field emission scanning electron microscopy (FESEM) and transmission electron microscopy (TEM). The FESEM and TEM images show that the MWCNTs are embedded along the nanofibers. Aqueous-based electrospinning of silk/PEO/MWCNTs composites provides potentially useful options for the fabrication of biomaterial scaffolds, e.g. wound dressings, based on this unique fibrous protein.

Abstract: Low pressure casting process was considered for fabrication of FeCrSi metal fiber reinforced A366.0 aluminum composites. FeCrSi/A366.0 alloy composite was fabricated by applied pressure 0.8MPa. The microstructure features, tensile strength and fatigue life of composites were investigated from room temperature to high temperature. It was confirmed that the FeCrSi metal fiber did indeed have a strengthening effect on the composite, lending it good mechanical properties and a good fatigue life at high temperatures.

Abstract: Superplastic boronizing (SPB) is a new surface hardening technique utilizing the ultra high plasticity phenomenon in metals in carrying out boronizing process. In boronizing, boron atoms are diffused into the metal substrate to form a hard boride layer. In this research, a new compression method for the SPB process was introduced. A clamp with an initial compressive load of about 1960 N was used. Thermo-mechanical treated duplex stainless steel (DSS) with fine grain microstructure which can show superplastic behavior at high temperatures was used as the superplastic material. SPB experiments were conducted at temperatures between 1123 and 1223 K for durations of 1 - 6 hours. The boronized specimens demonstrated thin, smooth and compact morphology of boride layer. The boride layer thickness was within ±10 0m - ±46.2 0m. On the boride layer, only the favorable single phase of Fe2B was detected. High value of surface hardness was observed in the range of ±847 HV - ±2914 HV. The overall results from the study show that the SPB process can significantly improve the surface properties of DSS.

Abstract: The silicon-containing polyimide/BaTiO3 nanocomposite films were prepared by mixing the silicon-containing poly(amic acid) based on bis(3,4-dicarboxyphenyl)dimethylsilane dianhydride and 4,4'-Oxydianiline with BaTiO3 nanoparticles, followed by thermal imidization. Structure and properties of the nanocomposite films were measured with FTIR, SEM, XPS and DMTA. The results indicated that the interfacial interaction between BaTiO3 nanoparticles and the silicon-containing polyimide was conspicuous, and that BaTiO3 nanoparticles appeared to be better dispersed in the polyimide matrix at a higher BaTiO3 concentration than at a lower one. The siliconcontaining polyimide/BaTiO3 nanocomposite films exhibited higher storage modulus and glass transition temperature than the original polyimide. It was also found that the infrared emissivity of the nanocomposite films varied with the content of BaTiO3 in the nanocomposites, and the nanocomposite films exhibited lower infrared emissivity value than the corresponding polyimide by measure of infrared emissivity.

Abstract: Stitched laminates is a low-cost structure panels with carbon fiber face sheets, and through-the-thickness Kevlar stitching. Through-the thickness stitching is proposed to increase the interlaminar strength and damage tolerance of composite laminates. Tensile and shear experiment of stitched laminates at room temperature and in hygrothermal environment was carried out according to corresponding national standards. Experiment results indicate that the tensile and shear modulus and strength were much reduced by the stitching, especially in hygrothermal environment. Micrographs of fracture appearance showed that the exist of resin-rich area is the source of crack both in normal room temperature environment and hygrothermal environment. It is concluded that hygrothermal environment and initial crack in resin-rich area were prime reason for performance lost of stitched laminates.