摘要:

The possibility of experimental model analysis in which stress birefringence is utilized for the simple and accurate evaluation of the tensile stress distribution in short-fibers embedded in composites has been investigated. For this purpose, a birefringence-free polymer blend is used as the matrix resin to avoid any influence of stress birefringence. When the stress applied to the composite is low, the experimental results agree with the theoretical estimates; however, as the stress increases, a slight deviation is detected.

DOI:10.1163/156855496X00100

出版商:Taylor & Francis Group    

年代:1996

数据来源: Taylor

摘要:

The radical graft polymerization of vinyl monomers onto carbon whisker, i.e. vapor grown carbon fiber, initiated by azo groups introduced onto the surface has been investigated. The introduction of azo groups onto the surface is achieved by (1) the reaction of 4,4'-azobis(4-cyanopentanoic acid) with isocyanate groups on the surface, which are introduced by the treatment of surface carboxyl and phenolic hydroxyl groups with tolylene-2,4-diisocyanate and (2) the reaction of 2,2'-azobis(2-cyano-n-propanol) with acyl chloride groups on the surface, which are introduced by the treatment of surface phenolic hydroxyl groups with terephthaloyl dichloride. The carbon whiskers having azo groups prepared from the above two methods are abbreviated as CW-Azo 1 and 2, respectively. The azo group content of CW-Azo 1 and 2 is determined to be 0.04 and 0.07 mmol/g, respectively. It is found that the radical polymerization of methyl methacrylate and styrene is initiated by the surface azo groups to give the corresponding polymer-grafted carbon whisker. The polymer-grafted carbon whisker gives a stable colloidal dispersion in good solvents for grafted polymer.

DOI:10.1163/156855496X00119

出版商:Taylor & Francis Group    

年代:1996

数据来源: Taylor

摘要:

Ultra-high tensile modulus (700 GPa) pitch-based carbon fiber was systematically surface treated, and interfacial shear strength (IFSS) between the fiber and epoxy resin was measured by micro-droplet method; then, relations between the IFSS and several mechanical properties of the corresponding CFRP were investigated. First, the method of measuring IFSS of very thin and fragile fiber by micro-droplet technique was developed by modifying the shape of specimen. IFSS was related to fiber surface oxygen, which seems to be related to functional groups on the fiber surface. Next, 0° tensile, 0° flexural and 0° compressive properties, 90° tensile strength, interlaminar shear strength (ILSS), and 0° Izod resistance were measured and were related to the IFSS. On the 0° compressive test, delamination was not the dominant failure mode and hence the compressive strength did not change with IFSS. ILSS was measured by double notch shear method, and was proportional to the IFSS. 90° tensile strength increased with increasing IFSS, and it saturated because of the transverse fiber failure. The results of other properties were also discussed.

DOI:10.1163/156855496X00128

出版商:Taylor & Francis Group    

年代:1996

数据来源: Taylor

摘要:

The primary objective of this work is to identify the effects of testing speed and the fiber surface treatment on the crushing performances of glass cloth/epoxy composite tubes. Two kinds of composite tube were investigated; the first tubes were reinforced with glass cloth treated with aminosilane coupling agent, and the others were reinforced with glass cloth treated with acrylsilane coupling agent. Composite tubes were axial compression tested at an impact speed of 8.5 m/s. The impact test results were compared with the results of tubes tested at a quasi-static crushing speed of 1 mm/min. Independent of the testing speed the aminosilane-treated tubes displayed higher energy absorption capability than the acrylsilane-treated tubes. The progressive crushing mode and the energy absorption capability of aminosilane-treated tubes was not influenced by the testing speed. By changing the testing speed from quasi-static to impact, the energy absorption capability of acrylsilane-treated tubes increased by 15%. The change in the energy absorption performance was related to the variation of crushing mechanism of acrylsilane-treated tubes with the testing speed.

DOI:10.1163/156855496X00137

出版商:Taylor & Francis Group    

年代:1996

数据来源: Taylor

摘要:

Sorption and dynamic mechanical analysis have been used to study the surface structure of high strength polymeric fibers including aramide and high modulus polyethylene fibers. The method used probes surface layers of the order of micrometers. The change in diffusion coefficient as a function of the radial distance of the fiber indicates structural inhomogeneity, in particular skin-core morphology in these fibers. The skin layer possesses lower density and less order than the fiber bulk.

DOI:10.1163/156855496X00146

出版商:Taylor & Francis Group    

年代:1996

数据来源: Taylor

DOI:10.1163/156855496X00155

出版商:Taylor & Francis Group    

年代:1996

数据来源: Taylor