Advanced Materials Research Vols. 160-162

Abstract: In-situ FT-IR technique is used to investigate the polymerization of propylene oxide with potassium t-butoxide as initiator. The epoxy absorbance at 828 cm-1 is the most useful peaks to monitor the reaction. The absorbance of C-O-C stretching vibration at 1107 cm-1 is very strong and also very useful. Yet, the absorbance of C-H stretching vibration in 3000~2800 cm-1 region is very weak and not reliable for In-situ FT-IR analysis. By monitoring the consumption of propylene oxide, the polymerization rate constant k at 33°C was calculated out and an interesting auto acceleration phenomenon was discovered. Moreover, the chain-transfer process was analyzed by measuring the formation of C=C double bonds, which clarified a former confusion about the course of propylene oxide rearrangement.

Abstract: With the extensive use of composite materials in aviation industry, the research of factors which affect their basic performances in production and usage has become very important. In this paper, a finite element analysis model is built by the commercial software MSC.Nastran / Patran to research the effect of fiber lay-up direction misalignment on the natural frequency of composite laminates. The results show that, in the same boundary conditions, stacking sequence has a significant impact on the natural frequencies and vibration modes of composite laminates, and in the lay-up process, the natural frequency change of laminates caused by 0° fiber lay-up direction misalignment is much larger than the natural frequency change of laminates due to 90° fiber lay-up direction misalignment. In the process control and certification of composite laminate plates lay-up, special attention should be taken to the inspection of 0° direction fibers.

Abstract: With the extensive use of composite materials in aviation industry, the research of holes which affect composite residual strength has become very important. Based on MSC.Nastran, the stress of each laminate unit was calculated. Failure factor of composite laminates containing holes were calculated with the Tsai-Wu failure criterion. In this paper, the influence of hole shape and size on the composite laminate failure factor under compressive loading was studied. The relationship of hole shape, size and residual strength of composite laminates was briefly discussed. The results show that, under compressive loading, the stress concentration appears near the hole, there is a proportional relationship between the failure factor and hole size, the hole size and residual strength is the inverse relation.

Abstract: Phase structure and micromorphology of gibbsite after hydrothermal treated in different solvents were studied. Results showed that there was a relationship between micromorphology and phase structure of as-synthesized product. The cubic slice-like boehmite microstructure can be obtained in water. The 3D flowerlike boehmite microstructure can be obtained in isopropanol or sodium carbonate solution. The global ammonium aluminum carbonate hydroxide (AACH) architectures assembled by the lathes can be obtained in urea solvent. Gibbsite can transform to boehmite after 12h hydrothermal treatment in water. In isopropanol or sodium carbonate solution, this time decreased to 6h. In urea solution, Aluminum hydroxide turned from gibbsite to the mixture of boehmite, gibbsite and AACH. Finally, AACH is synthesized. This procedure needs 24h.

Abstract: The three dimensional finite element model of composite laminates made of carbon fiber reinforced bismaleimide resin is built, and the stress state of the composite laminates under unidirectional tensile force is analyzed. The strength criterion and damage mode are given based on the stresses of material principal direction. The three dimensional finite element models of the same laminates with non-penetrating damage repaired by two kinds of bonding methods are built. The strength criterion and the damage mode of the two kinds of repaired models are also given. The influence of the interlaminar stress is considered in these analysis models. It is showed that the three dimensional models can simulate the geometric and physical features of the real composite laminates. It is concluded that the original composite laminates and the repaired ones both damage first in the laminar whose second material principal direction coincides with the axial tensile force. The damage mode is resin crack under tensile stress. The strength of the bonding patches is higher than the mother laminates. After scarf bonding repair, the strength of the damaged laminates recovers up to about eighty-four percent. With additional surface patch, the strength of the damaged laminates recovers up to about eighty-nine percent. Surface patch can improve the strength of damaged laminates.

Abstract: The three dimensional finite element model of composite laminates made of carbon fiber reinforced bismaleimide resin is built, and the natural vibration of the square composite laminates with clamped edges is analyzed. The natural vibration frequencies and modes of laminates without damage are given based on finite element method. The three dimensional finite element models of the same square laminates with non-penetrating damage repaired by two kinds of bonding methods are built. The natural vibration frequencies and modes are also given. It is showed that the three dimensional models can simulate the geometric and physical features of the real composite laminates. It is concluded that the natural vibration frequencies of the composite laminates all increase after it is repaired either by scarf bonding method or scarf and surface bonding method. After scarf bonding repairing, the lowest natural frequency increases about 3.6% and the second natural frequency increases 3.7%. After scarf and surface bonding repairing, the lowest natural frequency increases about 4.5% and the second frequency increases about 6.4%. The natural vibration modes of different repairing models are similar. The increase of natural frequencies may cause temporary vibration of aircraft skin made of composite laminates. The risk of resonance caused by bonding repairing is small.

Abstract: To complete the explanation on the mechanism of the Poly-3-hydroxybutyrate (PHB) synthesis intracellular in methanotrophs, the role of nicotinamide adenine dinucleotide (NADH) in the PHB synthesis mechanism in Methylosinus trichosporium IMV 3011, which can utilize methane and methanol as source of carbon and energy to synthesize PHB, was studied. The study carried on by using carbon monoxide (CO) as NADH consumption substrate or using sodium formate as NADH production substrate. The results showed that NADH influenced the synthesis and accumulation of PHB intracellular to some extent. Especially, the yield of PHB would decrease to 13.5% (compared to normal yield of 21.3%) under NADH deficiency condition caused by CO at content of 20%. During the flask fermetation process of Methylosinus trichosporium IMV 3011, adding CO with certain centent (10%, v/v) or at right time (72h) into gas mixture would keep the NADH intrcelluar at appropriate concentration, which will be avialable for cell growth and PHB accumulation. The findings on the NADH will greatly contribute to the less expensive production of PHB by methanotrophs and promote the application in this field.

Abstract: GT propellant with different storage life was obtained by aging test. The stabilizers (AkII and Res) content and methyl violet test burst time of the samples were measured by GC and methyl violet test instrument. The relationships of tb vs. ta, tb vs. R and R vs. ta were determined. The results show that the variation regularities of tb with ta and Res content with ta are very similar, and the variation regularity of tb with Res content is linear relationship. In addition, the Scattering field of methyl violet test burst times is very small. So, it is feasible that the stability evaluation of GT propellant with methyl-violet burst time.

Abstract: In the paper, a Ni-base composite cladding was cladded on the surface of QAl9-4 aluminum bronze by laser cladding technology, as well as its microstructure and tribological properties are studied. The results show that the microstructure of laser cladding is affected by solidification rate, and its wear behavior mainly lies on microstructure and lubrication condition. The microstructure of laser cladding is made up of cellular crystal and dendrite crystal. The microstructure of the surface cladding is cellular crystal, the middle section is crassitude dendrite crystal, and the bottom is coarse dendrite crystal and cellular crystal. Under dry friction condition, wear mechanism is abrasive wear and shedding strengthen phase, which has higher volume’s wear rate. Under lubricate condition, wear mechanism is abrasive wear and adhere wear, which has lower volume’s wear rate than that of dry friction. The average friction coefficient of the cladding under dry and lubricate condition are 0.39 and 0.15, the volume’s wear rate are 7.88×10-8mm3/N.mm and 1.56×10-9mm3/ N.mm, respectively. Therefore, the cladding has favorable wear resistance property under lubricate condition，and can be used as an excellent wearable material.

Abstract: A damage evolution law for porous phenolic composites is developed by using phenomenological point, which along with the improved Johnson-Cook model is then implemented into a finite difference code for one-dimensional strain wave problem. The velocity history of free-face particle is recorded and correlated with the simulated result to evaluate the damage parameters. Good agreement shows that the proposed damage evolution law and spall rule are feasible. Besides, the relationships between the striking velocity of flyer and the spall thickness as well as spall time are investigated. This study provides a methodology to quantify the damage evolution of phenolic composites under impact loading.