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11.
《Composite Interfaces》2013,20(4):309-322
The development of high-performance polymer composites is tightly bound with the functional surface modification of reinforcements. A new method, based on the principle of the fiber-bundle pull-out test, is proposed to analyze the interfacial properties between the long fibers in the form of a bundle and the polymer matrix. Specimen geometry and a test fixture were designed using finite element analysis. The method was verified for unsized and sized glass fibers embedded in polyester resin to demonstrate its applicability for a wide range of adhesion between fibers and the polymer matrix. The pull-out test can be used for a relative comparison of different surface modifications if the bundle geometry is unknown. The results of high reproducibility and sensitivity for interfacial properties make the method attractive. 相似文献
12.
《Composite Interfaces》2013,20(2):165-176
Because of the importance of thermal residual stresses in composite materials, our study aims to compute them by the finite element method. Numerical analysis shows that these stresses need to be taken into account. The interface is affected by these stresses, particularly in the free edge. The discontinuity of the normal stresses along the interface and the shear value at the free edge influence the composite material behaviour during its use (e.g. the composite used as a patch for repairing a crack). 相似文献
13.
《Composite Interfaces》2013,20(3-4):311-324
The fracture and debonding behavior of the Al2O3 layer coated on a ductile aluminum substrate wire was studied experimentally and analytically. When tensile strain was applied, the brittle Al2O3 coating layer showed multiple cracking perpendicular to the tensile axis. After the multiple cracking, compressive fracture of the Al2O3 layer arose in the circumferential direction when the layer was thinner than around 30 μm, while interfacial debonding between the Al2O3 layer and aluminum substrate arose when it was thicker. Such a difference in behavior between thin and thick layers could be accounted for by the difference in the layer thickness-dependence of the tensile radial stress at the interface and the compressive hoop stress of the Al2O3 layer calculated by the finite element method; the former stress increases while the latter one decreases with increasing layer thickness. 相似文献
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15.
《Composite Interfaces》2013,20(8):789-801
Interface design is an important topic in micro/nano electronic manufacturing. Interfaces of dissimilar materials in micro/nano electronic manufacturing are prone to crack initiations, leading to delaminations. The objective of this paper is to provide a systematic investigation to design or evaluate a bilayer film structure between Cu and Cr in micro/nano electronic manufacturing. In this paper, the Cu/Cr bilayer film prototype was deposited on the quartz glass by using RF magnetron sputtering. The elastic modulus and the hardness of the bilayer film prototype can be tested by using a nano-indenter. The test results show that the elastic modulus and the hardness of the bilayer film prototype are different at the difference maximum depth, h max. The elastic modulus and the hardness of the Cu/Cr interface are influenced by the nanometer indentation size effect and each single film. The elastic modulus of the bilayer film shows nonlinear characteristics which include increase at first and decrease on second stage. The change trend of the hardness also shows nonlinear characteristics which include a fast steady decline at first and a slow nonlinear decline on second stage. These results show that there are scale domino effects in micro/nano electronic manufacturing. Based on the test results, the mechanical properties of the interface are not the simple average of each composition film. There is very great difference in the interface. In the meantime, the finite element method is used to simulate the plastic property of the interface. The comparison between the simulation and the test shows that the modeling method is a valid investigating method to analyze mechanical properties for nano-interface structure. It builds a basis for a progressive study of the mechanical properties of a Cu/Cr interface structure. 相似文献
16.
Modelling of the transverse strength of fibre reinforced epoxy composite at low and high temperature
《Composite Interfaces》2013,20(3-4):379-394
Process-induced thermal residual stresses and matrix failure of unidirectional carbon fibre reinforced composites (CFRP) have been investigated by finite element analysis (FEA). We used a partial discrete FEA model based on a unidirectional composite consisting of a microscopic area of fibres and matrix surrounded by a homogenised composite area. The FEA provided information about the stress state in the matrix and the fibre–matrix interface. The transverse strength of the composite was calculated regarding matrix failure and fibre matrix debonding. The influence of the temperature on the Young's modulus, the non-linear stress–strain behaviour and the strength of the matrix were investigated in detail. Following this approach it was possible to incorporate the resulting microresidual stresses on the transverse strength of the composite. Tensile tests of the neat resin and of the composite were performed in the temperature range of ?40°C to 60°C. The results of the FEA modelling are in good agreement with the experimental results of the transverse tests. 相似文献
17.
《Quaestiones Mathematicae》2013,36(3):375-381
The growth conditions on the powers in the Gelfand-Hille theorems can be replaced by the same conditions on the Cesàro means, retaining the conclusions. Moreover, the assumptions can be further weakened on one of the two sides. 相似文献
18.
Stress intensity factors for a finite plate with an inclined crack by boundary collocation 总被引:1,自引:0,他引:1
Xing Li Xuemei You 《分析论及其应用》2005,21(3):258-265
In this paper, we combine the Muskhelishvili's complex variable method and boundary collocation method, and choose a set of new stress function based on the stress boundary condition of crack surface, the higher precision and less computation are reached. This method is applied to calculating the stress intensity factor for a finite plate with an inclined crack. The influence of θ (the obliquity of crack) on the stress intensity factors, as well as the number of summation terms on the stress intensity factor are studied and graphically represented. 相似文献
19.
E. B. Manoukian 《General Relativity and Gravitation》1997,29(6):705-714
A formalism is developed to compute the number density of gravitons, of specified energies, produced by an arbitrary external energy-momentum tensor source at any temperature. The formalism is applied to a simple Nambu string without making the usual assumption of a long wavelength approximation (L.W.A.). This exact result is also compared to the L.W.A. 相似文献