DOI:10.1163/156855497X00190

出版商:Taylor & Francis Group    

年代:1996

数据来源: Taylor

摘要:

—The preparation of calcium carbonate modified by 12-hydroxystearate groups and the grafting of polymers onto the surface by the polymerization of vinyl monomers initiated by azo groups introduced onto the surface were investigated. The preparation of calcium carbonate modified by 12-hydroxystearate was achieved by the reaction of calcium chloride with sodium carbonate containing a small amount of sodium 12-hydroxystearate. The introduction of azo groups onto calcium carbonate was successfully achieved by the direct condensation of the carboxyl group of 4,4'-azobis(4-cyanopentanoic acid) with 12-hydroxystearate groups on the modified calcium carbonate using N,N'-dicyclohexylcarbodiimide as a condensing agent. It was found that the radical polymerization of vinyl monomers, such as methyl methacrylate (MMA), styrene, and N-vinylcarbazole (NVC), was initiated by azo groups introduced onto the surface, and the corresponding polymers were grafted onto the surface based on the propagation of polymer from the surface: the percentage of grafting of polyMMA, polystyrene, and polyNVC reached 5.7, 9.5 and 3.5%, respectively, at 70°C. The percentage of grafting was found to decrease with decreasing monomer concentration. The wettability of calcium carbonate surface was found to turn from hydrophilic to hydrophobic by the grafting of polymers.

DOI:10.1163/156855497X00208

出版商:Taylor & Francis Group    

年代:1996

数据来源: Taylor

摘要:

The strength of GF/PP injection molded parts is reduced by the existence of a weldline. In this paper, the effect of molecular weight of matrix PP, GF content, GF surface treatment, GF shape (diameter and chopped strand length), MAH-PP content and interfacial properties on the weldline strength in GF/PP has been studied. Since the fibers orient vertically to the flow direction, effective reinforcement cannot be obtained at the weldline. Such fiber direction at the weldline cannot be controlled by the molecular weight of matrix, GF content and GF shapes. On the other hand, strength of the weld specimens increases when the amount of silane coupling agents and the MAH-PP content increase. Therefore, it is suggested that the weldline strength is affected by the strength of interfacial adhesion between GF and matrix.

DOI:10.1163/156855497X00217

出版商:Taylor & Francis Group    

年代:1996

数据来源: Taylor

摘要:

In estimating interfacial shear strength from the fragmentation process of fibers in single-fiber composites, a problem arises as to the value of the fiber strength if the fiber strengths distribute widely and strongly depend on the fiber length. To overcome this problem, a refined analysis method for simultaneously estimating the fiber and the interfacial shear strength from the fragmentation process has been shown. Agreements between the values estimated with the proposed method and the results of the single-fiber tensile and the direct shear tests have been obtained. It has been shown that the estimation of the interfacial shear strength using the proposed method is insensitive to the matrix properties if the interfacial shear strength is unaltered by the matrix properties, and that the variations of the distribution parameters of the fiber strength is significantly smaller for the proposed method as compared with the single-fiber tensile tests. The results obtained by applying the proposed method to various carbon fibers have been shown.

DOI:10.1163/156855497X00226

出版商:Taylor & Francis Group    

年代:1996

数据来源: Taylor

摘要:

Polypropylene sheets are treated with oxygen plasma for the interfacial control of GF/PP composites. The interfacial strength between glass fabric and PP resin is estimated by the T-peel test method. The evaluation of T-peel test data is done by both the T-peel strength method and the T-peel amplitude method. The T-peel strength value and T-peel amplitude value were respectively increased to about 50% and 120% compared with each value of non-treated specimens. The T-peel strength relates to the surface energy on the PP-sheet and the T-peel amplitude relates to the fracture pattern of the delamination surface. From SEM observations on the delamination surface, many voids in the space enclosed with fiber bundles are observed in the case of non-treated specimen and no void and fiber bridging are observed on the plasma treated specimens. It is found that interfacial properties between fiber and resin are improved by this plasma process.

DOI:10.1163/156855497X00235

出版商:Taylor & Francis Group    

年代:1996

数据来源: Taylor

摘要:

Tensile tests have been carried out on aramid knitted fabrics/epoxy resin composites in which the aramid knitted fabrics are treated with different sizing agents. Two kinds of surface treatment are performed; one uses an epoxy sizing agent and the other uses a polyethylene sizing agent. Tensile modulus and strength of epoxy-sized composites are higher than those of polyethylene-sized composites. The fracture process is different between epoxy- and polyethylene-sized materials. This difference in fracture process is caused by the different interphase made from either epoxy or polyethylene sizing treatments, resulting in the different tensile performance. Moreover, the tensile properties of the wale specimen are more affected than those of the course specimen by the interphase.

DOI:10.1163/156855497X00244

出版商:Taylor & Francis Group    

年代:1996

数据来源: Taylor

摘要:

During a fiber pull-out test, it is desirable to analyze the stress profiles along the embedded fiber directly within the same time scale as the normal pull-out tests. In the present study, the axial tensile stress profiles of the fiber in a model composite are measured during the single-fiber pull-out tests by using stress birefringence of the fiber. It is concluded from the analysis of the measured stress profiles that an effective radius of matrix, i.e. a radius defining the region of the matrix where the major deformation takes place, is not constant but is an increasing function of the interfacial shear stress. By incorporating the variable values of the effective radius of matrix into the shear-lag model, the axial tensile and the interfacial shear stress profiles are calculated. To accurately estimate the interfacial shear strength, the stress distribution along the embedded fiber and the variability of the effective radius of matrix should be taken into account instead of calculating the interfacial shear strength simply from the pull-out stress and the embedded length.

DOI:10.1163/156855497X00253

出版商:Taylor & Francis Group    

年代:1996

数据来源: Taylor