Papers by Keyword: Interfacial Property

Abstract: In order to improve the interfacial properties in carbon fiber (CF) reinforced epoxy (EP) composites, we directly introduced amidized carbon nanotubes (CNTs) dispersed in the fiber sizing onto the fiber surface. Morphology and surface energy of CFs were examined by scanning electron microscopy (SEM) and dynamic contact angle analysis test (DCAT). Tensile strength (TS) was investigated in accordance with ASTM standards. Mechanical properties of the composites were investigated by interlaminar shear strength (ILSS) and impact toughness. Test results indicate that TS, ILSS and impact toughness were enhanced simultaneously.

Abstract: Most of fracture processes of carbon/carbon composites (C/Cs) have been found to profoundly affected by their interfacial properties. A fiber-bundle pull-out test is utilized to determine the interface strength between fiber bundles and matrix of two kinds of C/Cs. Pre-fracture observations revealed that amount of voids and gaps existed in the interface, which make the interface strength decreases. The interfacial shear strengths of two kinds of C/Cs were all very low. Post-fracture observations revealed that a shear fracture was successfully induced within the carbon matrices at the loaded fiber bundle interface.

Abstract: The bundle/matrix interfacial strength in carbon/carbon composites was evaluated via the fiber-bundle pushed-out method. The determined data having a certain difference resulted from different interface fracture behavior via the analyses of the load-displacement curves of the loaded bundles and the observations of SEM images of the pushed-out bundle surface and its bundle/matrix interface. In order to better research bundle/matrix interface properties, Micro-CT was adopted to analyze bundle/matrix interface structure in c/c composites with nondestructive method, and its 2D and 3D images of real interfacial structure were obtained. Thus, the bundle pushed-out method, SEM and Micro-CT are better analysis and characterization methods of interfacial properties at bundle/matrix interface.

Abstract: UHMWPE fibers have widely application, but the poor adhesion to polymer matrix limit its development. Polymerization of vapor phase pyrrole on UHMWPE fibers was introduced in this paper for improve the adhesion between UHMWPE fibers and epoxy. The Ppy-coated UHMWPE fiber was studied by SEM, FTIR, DSC and pullout test, respectively. The result showed that there is no chemical act between UHMWPE fiber and polypyrrole. The Ppy coatings have strong effect on the morphological and adhesion property of UHMWPE fiber. The most important, the maximum pullout force was improved after pyrrole polymerization on the surface of UHMWPE fiber.

Abstract: In this paper, the effects of different metal contact treatments were systemically investigated. The interfacial properties between Au and CdZnTe (CZT) made by different methods including the electroless deposition, thermal evaporation and sputtering process were investigated by the Auger depth profiles, the adhesion force measurement, and the accelerated aging tests. The current-voltage (I-V) characteristics and the detector response to gamma-rays from 241Am for different Au contact treatments were also identified.

Abstract: Ceramic matrix composites (CMC) are very attractive materials for structural applications at high temperatures. Not only must CMC be damage tolerant, but they must also allow thermal management. For this purpose heat transfers must be controlled even in the presence of damage. Damage consists in multiple cracks that form in the matrix and ultimately in the fibers, when the stresses exceed the proportional limit. Therefore the thermal conductivity dependence on applied load is a factor of primary importance for the design of CMC components. This original approach combines a model of matrix cracking with a model of heat transfer through an elementary cracked volume element containing matrix crack and an interfacial crack. It was applied to 1D composites subject to tensile ant thermal loading parallel to fiber direction in a previous paper. The present paper compares predictions to experimental results.

Abstract: The interfacial property between graphite/epoxy laminate and multi-walled carbon nanotubes (MWNTs)/polymer nanocomposites was investigated. For the graphite/epoxy laminate, the fiber orientations were varied. For the MWNTs/polymer nanocomposites, the epoxy resins were used as the matrix material and the MWNTs were used as the reinforcement. The weight percentage of MWNTs in the MWNTs/polymer nanocomposites beam specimen was varied. The graphite/epoxy laminate and the MWNTs/polymer nanocomposite beam were glued together by epoxy to make the test specimens. To determine the interfacial property, the end notch flexure (ENF) method was used, and the specimen was placed in a three-point bending test to evaluate the critical strain energy release rate Gc. In analysis, the finite element method was used to obtain the numerical values of the critical strain energy release rate Gc and compared with the experimental ones.

Abstract: High modulus carbon/epoxy composites have been attached more and more importance in the aeronautic field. Because chemical inert of high modulus carbon fiber surface and its poor impregnation for resin, it is essential to improve its polarity in order to enhance the interfacial performances of high modulus carbon/epoxy composites. In this paper, high modulus carbon fiber was treated by ozone oxidation method to modify its surfacial properties. AFM and SEM were used to observe the surface of the carbon fiber, as well as interlaminar shear strength of high modulus carbon fiber/epoxy composite was tested. The impregnation and the interfacial performances of the high modulus carbon/epoxy composites were studied. The results show that after ozone treatment, the surface impregnation of high modulus carbon fiber and the interlaminar shear strength property of high modulus carbon/epoxy composites can be improved obviously.

Abstract: A new atomic strain concept is formulated that allows calculation of continuum quantities directly within a discrete atomic (molecular) system. The concept is based on the Voronoi tessellation of the molecular system and calculation of atomic site strains, which connects continuum variables and atomic quantities when the later are averaged over a sufficiently large volume treated as a point of the continuum body. The atomic strain tensor is applied to investigate interfacial properties of polymer based nanocomposites.

Abstract: Rubber-modified epoxy resins are used as a matrix material for glass and carbon-fiber composites. Mechanical properties of fiber reinforced composites depend on the interfacial shear strength between the reinforced fiber and the matrix resin. This study is focused on the interfacial shear strength in the reinforced carbon fiber and rubber-modified epoxy resin system. To evaluate interfacial shear strength between the fiber and the resin, pull-out test is performed using a microdroplet method. Based on experimental results, numerical analysis was also simulated. It is concluded that the interfacial shear strength of carbon fiber/unmodified epoxy resin system was higher than that of carbon fiber/modified epoxy resin system. The reason for decreased the interfacial shear strength of rubber-modified system is that contractive forces in neat epoxy resin acting on carbon fiber were less than those in rubber-modified epoxy resin system.