DOI:10.1163/156855494X00210

出版商:Taylor & Francis Group    

年代:1994

数据来源: Taylor

摘要:

The acylium perchlorate groups were successfully introduced onto the surface of a carbon whisker, i.e. a vapor-grown carbon fiber, by the reaction of acyl chloride groups on the surface with silver perchlorate in nitrobenzene at room temperature. The cationic ring-opening polymerizations of 1,3,5-trioxane and 1,3-dioxolane were initiated by the acylium perchlorate groups on the surface and the corresponding polyacetals were grafted onto carbon whisker: the percentage of poly(oxymethylene) grafting increased to 60%. The initiating activity increased with an increase in acylium perchlorate group content. Although the grafted poly(oxymethylene) on the surface was subject to stepwise thermal depolymerization from the chain end, the thermal stability was improved by acetylation of the end group. In addition, the acylium perchlorate groups on the surface have an ability to initiate the cationic copolymerization of 1,3,5-trioxane with styrene, styrene oxide, and 1,3-dioxolane. These polyacetal-grafted carbon whiskers produced stable dispersions in N,N-dimethylformamide.

DOI:10.1163/156855494X00229

出版商:Taylor & Francis Group    

年代:1994

数据来源: Taylor

摘要:

A model of finite element analysis was proposed to calculate mechanical properties of single ply of woven fabric composites considering interfacial properties. In this model, microfracture in the fiber bundle was regarded as interfacial fracture. Woven fabric structure was modeled using a pair of parallel beam elements expressing a fiber bundle and an interphase element between the two elements. Stress of the composite was calculated at the fracture of each element under tensile load, and the fracture process was simulated. The first fracture occurred in the interphase along the transverse bundle. Secondly, resin at the surface of the composite was seen to fail as did the longitudinal fiber. The stress of the composite at the interphase fracture was calculated with various properties of the interphase. The calculation showed that the lower modulus and higher strength interphase has high resistance to the microfracture. Another calculation was carried out with different weaving densities to evaluate the effect of the geometrical structure of the fabric on the microfracture. Weaving density was less effective than interfacial strength on the stress at the interphase fracture.

DOI:10.1163/156855494X00238

出版商:Taylor & Francis Group    

年代:1994

数据来源: Taylor

摘要:

Polymer modification of monodispersed colloidal silica (0.5 μm) and introduction of carboxyl groups on the surface are studied. The reactions of surface silanol with alternate copolymer silane coupling agents, prepared by maleic anhydride and styrene, methyl methacrylate or vinyl acetate, are effectively promoted by azeotropic removal of ethanol and water from the reaction system. Cross-linking of bound polymer on silica particles by esterification with diol results in simultaneous formation of carboxyl group of 0.15-0.21 mmol/g. The surface carboxyl groups are able to bind poly(methyl methacrylate) chains (Mn, 1700) of 0.86-1.29 mg/g by condensation reactions.

DOI:10.1163/156855494X00247

出版商:Taylor & Francis Group    

年代:1994

数据来源: Taylor

摘要:

Glass fabric was treated with sol-gel transition silicate gel to modify the composite interface. Micro roughness on the surface of the glass fabric was observed clearly by the atomic force microscope (AFM) at the surface of glass fabric which had been treated with a base catalytic silicate gel (b-SGSi). The specific surface area of this glass was 1.4 times that of the original glass fabric. The double cantilever beam (DCB) test was carried out on glass epoxy laminate composites, using b-SGSi glass fabrics and standard glass fabrics. In this test, the former laminate showed two fracture modes, stable and unstable crack growth, whereas the latter laminate showed only stable crack growth. In reference to the fracture toughness of the stable crack growth, the former laminate is about 1.4 times greater than that of the latter laminate. It was suspected that the difference was caused by the different interface bonding strength in the composite. The interfacial bonding was also tested by the soldering iron test and substantiated the superiority of b-SGSi glass fabric to standard glass.

DOI:10.1163/156855494X00256

出版商:Taylor & Francis Group    

年代:1994

数据来源: Taylor

摘要:

The effect of a variety of solvents on adhesion between polyethylene moldings and molten polyethylenes has been investigated. The adhesive strengths between the molten polyethylenes heated in the range of 250 to 300°C and the polyethylene moldings, on which organic solvents, such as xylene, decalin, tetralin and o-dichlorobenzene were precoated, sharply increased, and indicated stable high values. This effect was evident for such molten polyethylenes as LDPE, HDPE and HMWPE. This results from the local dissolution of the polyethylene surface and molten polyethylenes, and subsequent recrystallization of polyethylene molecules in both the surface of the molten polyethylene and polyethylene moldings as the solvents evaporate.

DOI:10.1163/156855494X00265

出版商:Taylor & Francis Group    

年代:1994

数据来源: Taylor

摘要:

The primary objective of this work is to identify the effects of testing temperature and the fibre/matrix adhesion on the crushing performances of composite tubes. Axial compressive tests were carried out on glass cloth/epoxy resin composite tubes at different temperatures ranging from - 140°C to 150°C. Two kinds of composite tube were investigated; the first tubes were reinforced with glass cloth treated with amino-functional silane coupling agent, and the others were reinforced with glass cloth treated with acrylsilane coupling agent. The crushing performances of aminosilane-treated tubes were higher than those of acrylsilane-treated tubes. The crushing performances of both kinds of tube decreased with increasing testing temperature. Room temperature tests produced crush zones of the splaying mode in aminosilane-treated tubes and fragmentation mode in acrylsilane-treated tubes. At low temperatures both the aminosilane-treated and acrylsilane-treated tubes were crushed by splaying mode. At high temperatures (80°C and 100°C) the crush zones of both the tubes contained features of splaying mode as well as fragmentation mode. At temperatures above 100°C tubes were buckled without progressive crushing. The changes in crushing mode were related to the variation of mechanical properties and frictional forces with the testing temperature.

DOI:10.1163/156855494X00274

出版商:Taylor & Francis Group    

年代:1994

数据来源: Taylor

摘要:

The micro-mechanical behavior of fiber/matrix interfaces and macroscopic mechanical properties of glass fiber reinforced Nylon 6 composites have been characterized for four different fiber surface treatments using in situ microscopic observation techniques. A pull-out test under an optical microscope is conducted to determine the interfacial bond strength of single-fiber embedded composites. An elasto-plastic axisymmetric finite element analysis is then used to explain the experimentally-obtained different failure mechanisms and processes at a broken fiber end. In addition, micro-deformation and failure process in injection-molded composites are observed under tensile loading in a scanning electron microscope (SEM) for specimens reinforced with randomly-oriented short glass fibers with the same fiber surface treatments. It is revealed that micro-damage and fracture characteristics in injection-molded thermoplastic composites are well correlated with micro-mechanical properties of fiber/matrix interfaces of single fiber composites.

DOI:10.1163/156855494X00283

出版商:Taylor & Francis Group    

年代:1994

数据来源: Taylor

摘要:

An investigation was conducted to check the effect of impregnation techniques on bending properties of glass fiber reinforced polyethylene terephthalate (PET). The impregnation techniques used commingled yarn and parallel yarn methods. Holding time during fabrication varied between 1 and 20 min. The morphology and thermal properties of the composites were studied by using scanning electron microscopy (SEM) and differential scanning calorimetry (DSC). The results showed that commingled yarn can be fabricated at low pressure with good impregnation characteristics whilst parallel yarn requires a high pressure before a good impregnation of matrix resin into fiber can be achieved. Bending properties of commingled yarn composites were higher than those of parallel yarn composites. This was due to different impregnation techniques. The crystallinity of the matrix resin was not affected by different holding time during compression molding.

DOI:10.1163/156855494X00292

出版商:Taylor & Francis Group    

年代:1994

数据来源: Taylor