Advanced Materials Research Vol. 410

Abstract: This work was try to study the relationship between the damping properties and the hydrogen bonds, fractional free volumes of nitrile-butadiene rubber (NBR)/hindered phenol (AO-80) composites from the microstructural point of view by combining the experimental and molecular simulation studies. The results indicated that the hydrogen bonds (HBs) were formed between AO-80 small molecules and NBR polymer chains. According to simulation results, because of the formed strongest HBs, highest binding energy and the smallest fractional free volume in the NBR/AO-80 composites with the blending ratio of 100/68, it contributed the maximum loss factor and highest modulus. It concluded that there was a suitable proportion of rubber blended with small hindered phenol molecules in the design of damping materials.

Abstract: A one-dimensional analytical scheme is developed for the dynamical response of sandwich plates having strength graded cores to shock impact. Results for in-air blast show that strength gradient distribution affects significantly the dynamic behavior of the sandwich. With fluid-structure interaction (FSI) taken into account, the approach is extended to underwater blast. It is demonstrated that whilst the influence of strength gradient distribution is noticeable on the impulse resistance, it depends strongly upon the core strength and FSI index. A gradient influence factor (GIF) is introduced to quantify the influence of different strength gradient distributions.

Abstract: Hail impact has been a long lasting threat for aircraft structures such as leading edges and forward sections. To mimic the physical process of hail impact on aircraft structures, a FEM model is established for all-metal sandwich structures having four different kinds of cores: corrugated core, pyramidal lattice core, metal foam core, and corrugation-foam hybrid core. Smoothed particle hydrodynamic (SPH) method is employed to predict the failure behavior of the hail, whilst the sandwich structures are described by a Lagrangian reference configuration. It is demonstrated that the sandwich structures with hybrid core outperforms the other three types for withstanding hail penetration as well as absorbing impact energy.

Abstract: Silicone rubber compounded with three different types of antibacterial agents: namely; nanoAg colloids, Silver substituted Zeolite compound (SSZ) and 2-Hydroxypropyl-3-Piperazinyl-Quinoline Carboxylic Acid Methacrylate (HPQM) were prepared and changes in antibacterial performance were assessed before and after exposure to UV light at different aging times. Drop plate and halo tests were performed to study the antibacterial performance of silicone rubber compounds. The results indicated that antibacterial activity of silicone compound changed when the UV aging time was increased. The antibacterial activity of the rubber added with HPQM extremely decreased considered by the inhibition zone and %reductions of Staphylococcus aureus and Escherichia coli bacteria for any given contact times. On the other hand, the UV light did not affect the antibacterial activity of silicone rubber compounds added with nanoAg colloids and SSZ agents.

Abstract: In this work, degummed (Bombyx mori)silk fabric was used as a bio-reinforcement for epoxy composite.The silk fabric was in a form of plain weaving with 177 ends/10 cm x 201 picks/10 cm. The degummed silk fabric (dSF)/epoxy composites were prepared by hand lay-up with dSF weight fraction of 0.18-0.35. The dSF was characterized using a universal testing machine (UTM) and a thermogravimetric analyzer (TGA). Mechanical properties including tensile properties, and impact property of neat epoxy and epoxy composites were investigated using a UTM and a impact testing machine, respectively. Thermal properties of neat epoxy and dSF/epoxy composites were investigated using a TGA. In addition, morphology of fracture surface of neat epoxy and dSF/epoxy composite were examined via a scanning electron microscope. Tensile strength of dSF was not significantly dependent in direction, was 537.1 N in warp direction, and 555 N in weft direction. In addition, dSF decomposed at 324°C under nitrogen atmosphere. The tensile strength and impact strength of the neat epoxy were higher than those of dSF/epoxy composites. However, tensile strength and impact strength tended to increased with increasing dSF content. On the other hand, Young’s modulus was improved by addition of dSF. The dSF/epoxy composites still fractured in a brittle manner.

Abstract: Hexagonal boron nitride (h-BN)/polyetheretherketone (PEEK) composite powders were deposited on carbon steel substrate via the flame spray coating technique. The content of hexagonal boron nitride with a mean particle size of 0.5 micrometer was varied from 2 to 8 wt% in this work. Tribological properties, namely specific wear rate and friction coefficient, at room temperature, 100 °C and 200°C were performed using Ball-on-Disc sliding wear test. At elevated temperature, h-BN could result in marked decrease in the friction coefficients and specific wear rates.

Abstract: In this work, hydroxyl-terminated lactic acid prepolymer was firstly prepared by adding diethylene glycol in the condensation of lactic acid. Molecular weight, acid value and structure of prepolymer were characterized. The results showed that the prepolymer was hydroxyl-terminated with weight average molecular weight (M_W) of 10,000 g/mol. After that, the chain linking polymerization of the prepolymer was carried out in a glass tube at 160 °C for 1 h employing 1,6-hexamethylene diisocyanate (HMDI) as a chain extender. By varying the hydroxyl/isocyanate ratio, it was found that the OH/NCO ratio of 1:2 seemed to be the most suitable ratio which gave PLA with the maximum M_W of 93,000 g/mol.

Abstract: Reaction injection molding process of phenolic foam sandwich plate was introduced in order to resolve the difficulties in repetitive continuous manufacturing process of such product. The phenolic foam produced here have uniform pore diameter, good fireproof property and there need not any glue between phenolic foam and color steel plate which could make it a potential building material instead of polysterol sandwich plate.

Abstract: Recently, the market for composite materials is dominated by small and medium series production and prototyping [1]. And the VaRTM (Vacuum assisted Resin Transfer Moldings) process is thought to be low cost composite fabrication technique [2]. The preforms in VaRTM are placed on one–side mold and they are sealed by a flexible vacuum bag [3]. The resin is infused into dry fabric formed on a mold near product shape under vacuum pressure and cured in an oven. In general, part defects often arise during the mold filling stage of the process, where a resin is drawn into performs through the use of vacuum. Uniform fill of resin and complete fiber saturation are required for fabricating high quality products [5]. So the resin flow control is extremely required. To solve these problems and short time fabrication, this article investigates the new molding process of C-FRP plate with using the combination of induction heating for quick heating and vacuuming method. To control of the volume fraction easily and to achieve homogeneous impregnation, thermoplastic resin sheet was chosen instead of liquid type. And the C-FRP in a size of 120mm*120mm and the thickness is 6.6mm was able to fabricate by this method.

Abstract: The polymer matrix composites (PMCs) are increasingly being used in structural applications owing to their superior mechanical properties. The in-service performance of composite materials requires them to perform under a variety of loading environments. Although a lot of research work has been done towards the mechanical characterization of PMCs, a lot remains to be done in special cases such as characterization of glass fiber reinforced plastics (GFRP) laminates with drilled hole. It is an established fact that drilling in composite laminates causes damage around the drilled hole and the damage influences the mechanical behavior of GFRP laminates under different loading conditions. The present investigation aims at studying the compressive behavior of GFRP laminates with drilled holes. The holes have been drilled at various input parameters (cutting speed, feed rate and drill point geometry) and the effect of these parameters on the compressive behavior of the GFRP laminates has been investigated using statistically designed experiments. It has been found that the drilling parameters significantly affect the compressive behaviour of laminates with drilled holes.