摘要:

The thermal residual stress induced in the fiber during specimen preparation, prior to a single-fiber fragmentation experiment, is studied using various theoretical schemes. It is found that the longitudinal component of this stress is compressive in nature, and that in some cases it is high enough to induce breaks in the fiber. The number of such pre-existing breaks may be calculated under certain conditions, one of them being that the Weibull shape parameter of the fiber compressive strength distribution be known. Experimental data produced with high-modulus graphite/polypropylene single-fiber composites are used to substantiate the arguments presented. Implications for high fiber content composites are discussed.

DOI:10.1163/156855494X00166

出版商:Taylor & Francis Group    

年代:1994

数据来源: Taylor

摘要:

The lamination of composite elements such as sheets or fibres made from ceramic powders represents a cheap and easy way of making tough ceramics. The fabrication and failure behaviour of such layered structures is described. It is shown that crack growth along the interfaces is dominated by dynamic effects due to the storage of excess elastic energy and that effects of loading state, in the silicon carbide/graphite system at least, appear to be relatively unimportant. Crack deflection at interfaces is also discussed and it is shown that observations made in these systems are not consistent with existing theories. Various possibilities are investigated.

DOI:10.1163/156855494X00175

出版商:Taylor & Francis Group    

年代:1994

数据来源: Taylor

摘要:

Composite films of different molecular weight poly(phenylene sulfide) (PPS) and three types of carbon fibers (Pitch, PAN, and Rayon-based fibers) have been studied by optical microscopy and wide-angle X-ray diffraction. Transcrystallization of growing spherulites on carbon fibers is found under all thermal conditions of growth on Rayon and Pitch-based carbon fibers for all types of matrices. For composite films with PAN carbon fibers transcrystallization of growing spherulites is not uniform and sometimes is not found at all. Existence of b axial orientation of twisted lamellae for transcrystalline zone of PPS is demonstrated by X-ray diffraction technique and compared with orientation of the stretched sample. The new induction time quantitative approach is applied to the transcrystalline growth of PPS spherulites on the surface of carbon fibers. The interfacial free energy difference for fiber/crystallite and heterogeneities/ crystallite systems in the melt that is defined from growth and nucleation studies are calculated and compared. The relative tendency for a polymer to crystallize at the fiber surface rather than in the bulk is demonstrated.

DOI:10.1163/156855494X00184

出版商:Taylor & Francis Group    

年代:1994

数据来源: Taylor

摘要:

A mesomechanical modeling approach was applied to estimate the influences of interfacial chemical reaction and interfacial bonding strength on tensile behavior and strength of fiber-reinforced metal matrix composites. First, a fracture mechanical model of single fiber coated with thin brittle surface layer was applied to describe strength of fiber on which interfacial reaction layer or artificial coating layer exists. With this model, influences of interfacial bonding strength between fiber and surface layer, difference in mechanical properties between fiber and surface layer, thickness of surface layer and discontinuity of surface layer on fiber strength were clarified. Second, a fracture model of multi-fiber composites in which shear-lag-analysis, fracture mechanics and a Monte Carlo simulation method were incorporated was applied to describe the fracture process and strength of composites. With this method, the influences of interfacial bonding strength between fiber and matrix in association with scatter of fiber strength, interfacial chemical reaction, ductility of matrix and volume fraction of fiber on fracture mode and strength of composites could be expressed successfully.

DOI:10.1163/156855494X00193

出版商:Taylor & Francis Group    

年代:1994

数据来源: Taylor

摘要:

Nuclear magnetic resonance is used to study the interface between (i) a polymer matrix and silica particles and (ii) two polymer components in a polymer blend.

DOI:10.1163/156855494X00201

出版商:Taylor & Francis Group    

年代:1994

数据来源: Taylor