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21.
《Composite Interfaces》2013,20(2-3):311-319
The transverse tensile properties of phenolic composites reinforced with spun-type carbon fabrics (spun C/P composites) have been investigated in order to evaluate the adherent failure behavior of composites in the transverse (90°) direction due to tension. The transverse tensile strength of the spun C/P composite is about 3.4 times higher than that of the conventional composite reinforced with filament type carbon fabrics (filament C/P composites). It is found from stress–strain curve of composites that it exhibits above 4 times higher failure strain than the filament C/P composite. However, the transverse tensile modulus of the spun C/P composite is similar to that of the filament C/P composite. The results indicate that the protruded fibers of spun yarns between the interlaminar layers in the spun C/P composite play an important role in improving the transverse tensile properties by the effects of fiber bridging. Consequently, this result suggests that use of spun yarn type carbon fabrics as reinforcement in a phenolic composite may significantly contribute to improving the interfacial properties of carbon/phenolic composites. 相似文献
22.
《Composite Interfaces》2013,20(8-9):819-830
In this work, the effect of composition, particle size and particle size ratio on the tensile properties of well-characterized hard/soft latex blends was investigated. Four blends of hard/soft latices, with varying particle sizes (either small or large), and volume fractions of 100/0, 80/20, 60/40, 50/50, 40/60, 20/80 and 0/100 were studied. The stress at break increased and the strain at break decreased as the amount of hard particles in the blend increased. A simple model, introduced by Pukanszky for filled polymers and polymer blends, proved to be a very useful tool for evaluating the tensile properties of the latex blends. Parameter B of the model could be related to the specific surface of the dispersed hard particles and the particle size ratio. Increasing the specific surface of the dispersed hard particles resulted in an increase in parameter B. The influence of particle size ratio on parameter B was shown to depend on the formation of aggregates. 相似文献
23.
《Composite Interfaces》2013,20(5-6):361-391
We propose a new model for characterization of strength properties of fiber-polymer interfaces by means of a single fiber pull-out test. Our model is based on shear-lag analysis using a bilinear bond law (stress–slip relationship) which, in turn, is a simplified representation of the true stress behavior as a function of strain for cold-drawing polymers. According to this law, the fiber-polymer interface is subjected to the following successive processes: (1) linear loading within the elastic region; (2) yielding and subsequent bond strengthening with increasing strain; (3) local debonding and interfacial crack propagation along the interface; (4) post-debonding friction. Both crack propagation and extension of the yielded zone can be stable and unstable, depending on the values of interfacial parameters and the load applied to the free fiber end. The procedure of construction of theoretical force–displacement curves for a pull-out test is described in detail. Theoretical curves exhibit such features as multiple kinks and non-linear regions, whose positions and shape are related to interfacial parameters. By fitting experimental curves with theoretical ones, these parameters can be determined for each separate pull-out specimen. Practical examples are provided for basalt fiber–polypropylene and glass fiber–polypropylene specimens. 相似文献
24.
Bing Na Qin Zhang Hong Yang Qiang Fu Yong-feng Men 《高分子科学》2007,(3):285-290
In this communication, by means of stress relaxation experiments, the viscous stress at various strains during tensile deformation of oriented polyolefin samples including high density polyethylene (HDPE), linear low density polyethylene (LLDPE) and isotactic polypropylene (iPP), has been determined. The viscous stress in the oriented samples takes up to 50%-70% of the total stress, which is unusually high compared with their isotropic counterparts. The unusual high viscous stress was discussed based on mainly the existence of shish structure in oriented polyolefins, which could enhance the inter-lamella coupling significantly. 相似文献
25.
Qin-jian Yin Xue Yun Zhao-jun Chen Wen Cao Qin Zhang Qiang Fu 《高分子科学》2007,(3):319-324
In order to improve the tensile properties of poly(ethylene terephthalate)(PET), we used the direct esterification method to synthesize PET in a home-made facility, and a certain amount of ethylene glycol (EG), one of the two starting monomers, was substituted by glycerin (GE). Four PETs with different GE contents were prepared to investigate the effect of GE on the crystallization and tensile properties of the prepared copolyester. The results showed largely improved tensile properties and increased crystallization temperature due to the possible crosslinking structure in PET by using a small amount of GE. 相似文献
26.
Silvestre Ragusa 《General Relativity and Gravitation》1999,31(3):275-286
The field equations of a proposed nonsymmetrictheory of gravitation are solved exactly for the case ofa static and spherically symmetric point singularity.The physical consequences of the solution are analyzed for the precession of perihelia,deflection of light, red-shift and radar-echodelay. 相似文献
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28.
《Composite Interfaces》2013,20(5-7):453-465
Diimides 4,4′-oxydiphenylene diphthalylimide (PT-ODA-PT) and diphenylbiphenyltetracarboxyimide (A-BPDA-A) of an evident affinity to polyimides have been dispersed in a matrix of poly(4,4′-oxydiphenylene biphenyltetracarboxyimide) (BPDA-ODA). Changes in thermal and mechanical properties of BPDA-ODA films modified by diimides have been found to depend on the amount of diimide added and the conditions of film preparation (stretching). It has been established that diimides can play two different roles. When dissolved in polyimide, they act as plasticizers improving the segment mobility of BPDA-ODA chains, which may be critically needed to achieve the better molecular packing. The films plasticized by diimides show lower T g and the order–disorder transition temperature; the unstretched films exhibit better tensile properties, compared to unmodified films. However, dispersed beyond the limit of solubility in polyimides, diimides have detrimental effects on mechanical properties of the films. Though changes of the thermal properties of compositions derived from BPDA-ODA polyimide and microparticular diimides are less expressed than those of polyimide films plasticized by diimides, the compositions have poorer ultimate strength and shorter elongation at break. The conclusion may be drawn that the mechanical properties of the films modified by microparticular diimide are mainly controlled not by the interfacial interaction matrix–microparticles, but more likely by the much stronger macromolecular chain–chain interaction. 相似文献
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《Composite Interfaces》2013,20(8-9):699-715
The present paper shows the potential of fumed silica as nano-reinforcements in polymers, by considering the limitations and challenges one has to face dealing with nanoparticles in general. The dominating effect of the manufacturing route and surface properties of fumed silica influencing the resulting degree of dispersion and the interfacial adhesion were investigated by electron microscopy (TEM, SEM). The resulting (fracture-) mechanical properties of the fumed silica/epoxy composites were investigated for volume contents of 0.5 vol% and below. Independent of the surface modification, static and dynamic modulus decreased slightly by adding the fumed silica. Hence, the fracture toughness K Ic turned out to be significantly increased (54%) adding only 0.5 vol% of surface modified fumed silica. 相似文献