Advanced Materials Research Vols. 123-125

Abstract: Shape memory polymers own many advantages compared with traditional shape memory alloys or ceramics. In order to improve their shape recovery stress and realize a stable recovery response during the deployable process, the structure of SMP sandwich beam composed of two metallic skin and one SMP core is considered. The recovery behaviors of pure SMP and SMP beams reinforced by one-layer metallic skin are also discussed for comparison. The results confirm that the deployable properties of SMP matrix can be significantly improved by using sandwich structure.

Abstract: Flexible fabric keyboard is a field of smart textile. It can overcome traditional horniness keyboard can’t be foldable and washing. Because conventional keyboard’s switch is matrix circuit, two conductive layers are not touchable due to action of a middle insulating layer in relaxing. When the key is pressed, two conductive layers contact and form electric current. In this laboratory study there are three kinds of structure designed such as through-thickness angle interlock, trapezia and X shape structure which consist of the support part and the orifice part. Conductive filaments are 8 roots for the warp and weft conductive material. Then the weaving time, elastic modulus and connection pressure are tested and analyzed for every kind of fabric keyboard switch. It is concluded that the weaving time of through-thickness angle interlock is the shortest and the elastic modulus of X shape structure is the best, but connection pressure of three kinds of structures is all big. These findings may assist in recommendations regarding the further development of flexible fabric keyboard.

Abstract: The purpose of this study is to present the optimal design technology on the broad band radar absorbing composite laminates. The design concept is based on the 2-layer Dällenbach type radar absorber, in which the composite laminates act as the lossy layers. The radar absorbing function was achieved by controlling the electromagnetic property of the composite laminates by means of adding carbon nano materials into the matrix resin of the fiber-reinforced composite laminates. The laminates were fabricated with the E-glass fabric/epoxy prepregs and cured in an autoclave. The electromagnetic properties were measured for the frequency band of 0.5 ~ 18.0 GHz using a coaxial air line and a vector network analyzer. The radar absorbers were designed to have optimal absorbing performance in 10 GHz. The optimization was conducted to get the optimal number of the plies of the laminates and filler contents of the carbon nano materials in the respective layers. The performances of the fabricated absorbers were measured to be compared with the design results. The discrepancy between the design and the measurement was discussed.

Abstract: A series of dimeric liquid crystalline (LC) epoxy monomers containing azo groups with different length of central spacers were synthesized. The mesogenic behavior of these monomers was characterized by differential scanning calorimetry(DSC), polarized optical microscopy (POM) and wide-angle X-Ray diffraction(WAXS). Like other dimeric LC epoxy monomers, the melting points, clear points and mesophase of these compounds were influenced by the carbon numbers of the central spacers. Cure kinetics of these monomers with anhydride was studied by non-isothermal DSC at different heating rates. With the increasing of conversion, the values of activation energy show a tendency to decrease. The formation and development of LC phase during curing were also studied by POM. Finally LC thermosets with nematic phase were obtained.

Abstract: This paper presents the discovery of a range of high-performance organic non-linear optical (NLO) materials, that arises from ‘smart material’ design and systematic search strategies. This systematization circumvents the previous use of iterative discovery methods, which can only ever afford incremental improvements to currently known NLO materials, and they have no capacity to reveal entirely new classes of suitable NLO materials. This new approach employs data-mining, using the world’s repository of all published organic crystal structures as a representative set of chemical space. Two independent search strategies are implemented, each predicting the best organic NLO materials. The first search method relies on the concept of ‘molecular lego’, taking particular types of molecular fragments that are known to be important constituents of an NLO active material (the ‘lego’), and searching for these through chemical space, with the assistance of graph theory algorithms and systematic enumeration and classification. The second search method uses quantum- mechanical calculations to evaluate the molecular hyperpolarizability, β, of every organic molecule in the aforementioned database. Since β affords the intrinsic measure of NLO output, all organic molecules listed in descending order of  values reflects a ranked list of their NLO potential. The NLO properties of selected materials that are highly-ranked in these two lists were then tested experimentally, using Hyper-Rayleigh Scattering (HRS). The predictions are shown to be borne out by such experiments: HRS results show β0 (static hyperpolarizability) values that are up to 10 x greater than those for the industrial reference Disperse Red 1. Due to the commercial potential of these results, four new classes of NLO materials identified by this study have recently been patented.

Abstract: Authors’ group has been done researches on the damage monitoring of the laminated Carbon Fiber Reinforced Plastic (CFRP) using the electrical resistance change method. The method adopts reinforcement carbon fibers as sensors, and it is called self-sensing method. Using thin CFRP laminates, delamination crack location and dimension are identified with the electrical resistance change method. However, the electrical resistance decreases when a delamination crack is made in a thick CFRP beam. The present paper experimentally investigates the effect of the dent for the measurements of electrical resistance change. Indentation tests are performed for the thick CFRP plates. The effect of the dent is calculated compared with the effect of piezoresistivity caused by the residual stress relief. As a result, the effect of the dent is larger than the effect of the residual stress relief for the thick CFRP. For the thick CFRP, dents cause the significant reduction of the electrical resistance in the thickness direction, and that causes electrical resistance decrease.

Abstract: In order to fabricate textiles with electromagnetic shielding effectiveness (EMSE) and far infrared emissivity, we fabricated bamboo charcoal/metal (BC/M) composite wrapped yarns with metal wires (stainless steel wires or copper wires) as the core yarn and bamboo charcoal textured yarn as the wrapped yarns using a rotor twister machine. The optimum manufacture parameters included: the speed of the rotor twister was 8000 rpm and the wrapped amounts of the BC/M composite wrapped yarns were 4 turns/cm. The BC/M composite wrapped yarns were made into the BC/M composite woven fabrics using a loom machine. Moreover, we tested the BC/M composite woven fabrics in EMSE and then changed the lamination angles. When the lamination amount was 6, laminated angles were 0°/45°/90°/-45°/0°/45°, 0°/ 90°/0°/ 90°/0°/ 90°, and the frequencies of the incident waves were between 1.83 and 3 GHz, the EMSE of the BC/M composite woven fabrics reached 50 to 60 dB which was satisfactory.

Abstract: The main objective of this study is to examine the two dimensional surface crack problems in a system with an interface between two elastic-plastic solids of different yield strength subjected to mode I mechanical loading. The surface cracks growth is considered to occure along the interface direction of bimaterials which is perfectly bonded to each others. A two dimensional finite elementmethod is used to solve the structural problem. Solid 183-node elements are utilized to simulate the strain singularity around the crack front. The crack surface is subjected to a compressive load by three point bending. The stress intesity factors are computed by using the displacement correlation technique. The primary goal is to develop a model crack tip stresses and strains in a manner that is useful for crack growth initiation and propagation in a FGM.

Abstract: Electrospinning has been used in a wide variety of applications, such as tissue engineering, filtration and biomaterial scaffolds for vascular grafts or wound dressings. Recently, wound dressings have become more important in human life. They must have the superior biocompatibility, water absorption, water vapor permeation and antibacterial ability. Chitosan has been employed in clinical applications and exhibits excellent biocompatibility, biodegradation and bacteriostasis. In this investigation OR study, experiments were performed on a series of poly (vinyl alcohol) (PVA)/Chitosan (CS) fiber membranes at various blend ratios and electric fields to evaluate their spinnability. The morphology, diameter and structure of electrospun nanofibers were examined by scanning electron microscopy (SEM). When PVA/Chitosan=80:20 and electric field=0.67 kV/cm, the spinnability of electrospun membrane was good. IR spectra demonstrated strong intermolecular hydrogen bonds between the molecules of Chitosan and PVA. Furthermore, cell cultures demonstrate that both PAV and chitosan have good biocompatibility and are non-toxic.

Abstract: Sodium alginate (SA) is a polyanionic copolymer consist of mannuronic(M) and guluronic(G) sugar residues, it has been comment used in biomedical applications. In this research, polylactic acid (PLA) and Tencel fiber were fabricated into PLA/Tencel composite nonwoven fabric. Then the gel aqueous Ca-SA was combined with PLA/Tencel composite nonwoven fabric by three-dimensional (3D) coating method to form porosity coating layer. Then LMWCS was sprayed on the whole surface to form antibacterial layer. The physical properties of novel wound dressing were evaluated such as tensile strength, tear strength, water absorption rate, stiffness and SEM. In SEM observation result indicated, the coating layer performs highly porosity structure. Between coating layer and PLA/Tencel composite nonwoven fabric was combined by physical bonding. In this way, PLA/Tencel composite nonwoven fabric can remain some part of air permeability and also enhance the strength of dressing.