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This work deals with the fiber ends debonding-induced elastic moduli degradation of a short fiber reinforced composite (SFRC). The strain fields of the matrix in a representative volume element (RVE) of the SFRC are determined from an imaginary fiber technique. By using the debonding boundary conditions, the debonded modulus of the composite is derived, which is affected by not only the far-field but also the transient solutions for the longitudinal strain of the matrix. Particularly, the imaginary fiber technique provides unbounded solution for a moderately large fiber aspect ratio. This is resolved by separating the RVE along the fiber direction into two domains. Combining the longitudinal strains in both domains, the longitudinal modulus is determined, and the longitudinal bridging tensor element in the micromechanics Bridging Model is amended. Five elastic moduli of an SFRC after the fiber end debonding are obtained on the amended Bridging Model. The effects of the fiber volume fraction, fiber aspect ratio, and fiber-to-matrix modulus ratio on the end-debonded longitudinal modulus, transverse modulus, and longitudinal Poisson's ratio are investigated. [ABSTRACT FROM AUTHOR]

Copyright of Journal of Ordnance Equipment Engineering is the property of Chongqing University of Technology and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

The characteristic of interphase has a significant influence on the macroscopic performance of carbon fiber-reinforced plastics (CFRP). To investigate the effect of interphase on composite elastic modulus, a representative volume element (RVE) of unidirectional CFRP with inhomogeneous interphase was established. Based on the bridging model, a theoretical calculation method of composite elastic modulus was given. The elastic modulus of T300/BSL914C composites was obtained by the theoretical method. Results are in good agreement with the finite element method and experimental data. Four types of interphase models were given including inhomogeneous transversely isotropic, inhomogeneous isotropic, homogeneous transversely isotropic, and homogeneous isotropic. The results demonstrate that interphase type has an influence on the prediction of CFRP composites’ elastic modulus. With the increase of thickness, the prediction error of elastic modulus caused by interphase type increases rapidly. Furthermore, the relationship between composite elastic modulus and interphase thickness and stiffness is analyzed. With the increase in thickness, the changes in shear modulus G 12 and Poisson’s ratio ν23 are more evident than in other elastic properties, and with the enhancement of interphase stiffness, the increase of G 12 is the most significant.

Accurately predicting ultimate strength of composite laminate is still a great challenge, especially only based on the constituent properties. In this paper, the micromechanics Bridging Model and systematic failure criteria for the constituent materials with emphasis on matrix failures subjected to three dimensional (3D) loads are compiled into a UMAT subroutine for ABAQUS to analyze failures of a laminated composite structure. The main purpose of this research is to greatly reduce calculation costs for loading conditions of in-plane tension or compression by introducing a simplified 3D finite element model based on the Pipes-Pagano theory. In all calculation cases, only the constituent properties together with the transverse tensile strength of unidirectional composite are needed as input data. Later in this paper, sufficient illustrations of 81 different composite laminates composed of 14 material systems are analyzed to confirm the practicability of this model. [ABSTRACT FROM AUTHOR]

This work provides a method to predict the three-dimensional equivalent elastic properties of the filament-wound composites based on the multi-scale homogenization principle. In the meso-scale, a representative volume element (RVE) is defined and the bridging model is adopted to establish a theoretical predictive model for its three-dimensional equivalent elastic constants. The results obtained through this method for the previous experimental model are compared with the ones gained respectively by experiments and classical laminate theory to verify the reliability of this model. In addition, the effects of some winding parameters, such as winding angle, on the equivalent elastic behavior of the filament-wound composites are analyzed. The rules gained can provide a theoretical reference for the optimum design of filament-wound composites.

An analytical approach is established to analyze the mechanical behavior of a unidirectional (UD) composite subjected to an in-plane shear. The effects of the interface debonding on the in-plane shear strength and plasticity of the composite are evaluated respectively. The volume-averaged internal stresses of the fiber and matrix are calculated through Bridging Model. Owing to the stress fluctuation in the matrix caused by other phases (such as the imbedded fiber and interface crack), the homogenized matrix stresses must be converted into true values based on a stress concentration factor (SCF). A new in-plane shear SCF of a composite with debonded interface is derived and applied to the predictions of strain and strength in this paper. Moreover, the contribution of the relative slippage between fiber and matrix to the non-linear shear deformation of the composite is analyzed. Finally, the efficiency and accuracy of our theory are verified with a series of examples. The approach is very efficient because the calculation can be achieved with explicit expressions mainly based on the constituent material properties. The comparisons between predicted strength and deformation with the experimental results show that our analytical approach can give out reliable underlying data for multi-scale analysis. Moreover, this theoretical method can tell if and how much the interface of a composite needs to be modified for a given load environment. [ABSTRACT FROM AUTHOR]

The laminate is essentially bonded together to form the individual laminate by the matrix, any delamination of the laminate must be initiated from a matrix failure. Based on this viewpoint, the initiation of laminate delamination was predicted through analyzing the stresses of the matrix. A three-dimensional finite element method is used to calculate the stress field of a symmetrically laminated plate under an axial load. A convergence study was performed and an average stress method was proposed to solve the singularity problem. Then the internal stresses in the fiber and matrix were determined in terms of the bridging micromechanics model. Finally, a Mohr criterion was used to detect the failure of matrix. T800/914 angle-plied laminates were considered. The results show that this approach is able to correlate reasonably with the available experimental data.

The article is aimed at studying the process of the State regulation of the labor market from the standpoint of strategic and stakeholder-oriented approaches. The strategic approach to formation of the conception of the State regulation of labor market is researched. Within the framework of the strategic approach the selective strategy of formation of the mentioned conception is considered. The basic criteria of formation of the selective strategy are defined. The stakeholder-oriented approach to formation of the conception of the State regulation of labor market is explored. A definition of the concept of stakeholder of labor market is formulated. The process of interaction of stakeholders in the labor market is characterized with the help of the bridging model based on bipartism, tripartism and multipartism. It is concluded that the process of forming the concept of the State regulation of labor market should be based on strategic and stakeholder-oriented approaches. The strategic approach involves the implementation of a selective strategy. A stakeholder-oriented approach emphasizes the need to achieve a balance of interests, which consists in organization of the public and economic space of the labor market through the efficient implementation of joint-distribution relations.

As a laminate is essentially bonded together from laminae by the matrix, any delamination of it must be initiated from a matrix failure. This article predicts the initiation of a laminate delamination through analyzing the matrix failure. A three-dimensional finite element approach is used to calculate the stress field of an angle-plied laminate under a uniaxial tension. The stresses in each lamina of the laminate are averaged with respect to the lamina thickness to eliminate a weak singularity near a free edge. Homogenized stresses in the matrix are then obtained through bridging model, which are further converted into true values by virtue of stress concentration factors of the matrix in the composite. Influence of any interface crack between the fiber and the matrix on the true stresses has been taken into account. A criterion for detecting the delamination initiation is proposed, which only involves the true stresses and the original strength data of the matrix. To assess the efficiency, comparisons between the predictions and available experiment data are made for a number of angle-plied laminates. Reasonable correlation has been found. [ABSTRACT FROM AUTHOR]

Developing a unified theory to describe granular matter, which can behave like either solid or fluid, is one of the grand challenges in modern science. This is mainly because the current theories, rooted in different origins, interpret granular matter from disparate perspectives and are hard to merge. In this work, we demonstrate that it is possible to generate such a generic theory by bridging the elastoplastic theory of solids with the rheological law of granular flow. The proposed theory or mathematical model can well explain the avalanching behaviours occurring in solid-fluid phase transition, and other related concepts such as interparticle interlocking, dilatancy, hysteresis, scaling law, and flow regimes in describing granular matter. Its applicability is tested in a variety of granular systems where solid- and fluid-like states coexist. This work therefore offers a simple but general theory to describe granular matter in a unified way. [Display omitted] • A theory is proposed for granular matter by bridging elastoplasticity and rheology. • The solid-fluid transition behaviour is theoretically modelled. • The roles of interlocking, dilatancy, hysteresis and particle size are considered. • The model is tested at various solid- and fluid-like granular states. [ABSTRACT FROM AUTHOR]

Copyright of Pedagogische Studien is the property of Vereniging Onderwijsresearch and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

The multi-filamentary Bi2Sr2CaCu2O8+x (Bi-2212) round wires are made of superconducting filaments, metal Ag and Ag alloy, which are typical composite structure. Since the filament is brittle, there are various defects and cracks in the Bi-2212 round wire after heat treatment. In this paper, we assume that the filaments in the wire are uniformly arranged. Adopting the bridging model which is often used in the fiber-reinforced composite, we calculate the ultimate strength of the round wire. The effects of the volume fraction, elastic modulus and interface shear strength are discussed in detail. [ABSTRACT FROM AUTHOR]

This article presents a multi-scale progressive micro-mechanical fatigue model. The model employs fundamental equation of the kinetic theory of fracture to calculate damage parameters of both fiber and matrix during cyclic loading. In order to adapt the equation, required material coefficients of the constituents can be achieved from fatigue test results of longitudinal and transverse unidirectional composites, only. Sharing stress capacities of fiber and matrix are determined using a modified progressive micro-mechanical bridging model in the presence of damage. The damage parameters in the constituents are calculated employing two different equivalent scalars. However, during sinusoidal load application, these damage parameters are also updated using a first kind Bessel function of amplitude stresses in the constituents as well as their material coefficients. The enhanced formulation is then implemented into the commercial finite element software of ABAQUS via a developed user material (UMAT) subroutine utilizing a suitable failure criteria and an own solution algorithm. Advantages of the proposed model are assessed and comparisons with available solutions are presented. [ABSTRACT FROM AUTHOR]

Bridging tensor is fundamental to the Bridging Model for prediction of thermomechanical and strength behaviors of a fiber reinforced composite based on constituent fiber and matrix properties. This paper focuses on derivation of the bridging tensors with an imperfect fiber–matrix interface. Using a three-phase coaxial cylinder assemblage (CCA) model, the stress fields in all of the three materials in the assemblage when subjected to six kinds of loading conditions are obtained by means of rigorous elasticity theory. The stresses are then averaged with respect to the corresponding phase volumes. By imposing that the averaged stress components in each phase be correlated with those in an adjacent phase through a bridging tensor and solving the resulting simultaneous linear algebraic equations, the bridging tensor elements are determined. Comparison of the thus obtained effective off-axis moduli with experiments for a SCS-6/Ti unidirectional (UD) composite is made to show the efficiency of the three-phase bridging tensors. Effect of interphases on the effective elastic properties and stress ratios of the composite with different coatings is investigated. [ABSTRACT FROM AUTHOR]

Three theoretical microstructural models were constructed based on manufacturing three-dimensional seven-directional (3D7d) braided preforms, and their relationships with braiding angles, fiber volume fractions, and yarn filling factor were investigated. The influences of braiding parameters, loading directions, and braiding structure on the performances of 3D7d braided composites were predicted in combination with a bridging model. The results concluded that the longitudinal modulus and tensile strength decreased with increasing braiding angles, while the transverse modulus and strength were opposite, and the performances of composites were better at higher fiber volume fractions. Compared with 3D4d braided composites, the transverse strength of 3D7d braided composites improved significantly. Furthermore, the three microstructural models were damaged in the order of interior, surface, and corner unit cell models during tensile loading. Especially, the fifth and seventh yarns within unit cell models were damaged firstly under longitudinal and transverse loads, respectively. This method adopted in this work provides a basis for predicting the mechanical properties of 3D7d braided composites. • Three microstructural models of 3D seven-directional braided preforms were created. • The tensile properties of composites were predicted by combining a bridging model. • 3D seven-directional braided composites have excellent integral performances. [ABSTRACT FROM AUTHOR]

The Nb 3 Sn strands which have high critical field are used in cable-in-conduit conductors (CICCs). The superconducting strands are twisted multistage and experience complex thermal and electromagnetic loadings. Due to their brittleness, the cracking of the Nb 3 Sn filaments will occur under mechanical loading. In this paper, based on the linear elastic fracture theory, we study the effects of tension loading on the fracture behavior of central crack firstly. The strain energy release rates for different twist pitches and cabling stages are presented. As the triplet is subjected to the uniaxial strain, the cracking probability will increase with the twist pitch. The crack number increases with the applied strain, and wider filament or bronze can lead to smaller crack number under the same applied strain. In addition, multistage cabling has better mechanical stability. Next, the two collinear crack problem is considered. The variations of microcrack number show that the wider bronze can provide more resistance for the propagating of the large cracks. We can conclude that the bronze plays an important role in improving the stability and strength. [ABSTRACT FROM AUTHOR]

Collaboration between university and industry has long existed, but the rapid increase of global knowledge has increased the demand for strategic relationships that go beyond the conventional funding of research projects. University research should be developed in future to play an important role in industry and in turn economic growth. For a successful collaboration, both sides should overcome the communication and cultural divide that impair university–industry relationships across all categories and undercut their potential. Faculty of Engineering at Rabigh (FER) – King Abdulaziz University (KAU) is strategically located near major industries and facilities such as Petro Rabigh, desalination plant, steel fabrication, and cement industries, which makes FER a nucleus to solve technological problems for all these industries. Much effort has been made at FER to collaborate with these industries through mutual reciprocal visits of university and industry personnel as well as student internships. These are aimed to solve both short- and long-term technological issues at the industrial units. This will not only improve the local knowledge base and skills, but also bring confidence and trust between the two partners. It is well known that innovation does not take place in vacuum: a context – the economy, society, and policy – determines how easy or difficult it is to innovate. In this context, the role of government is also very important to create legislations that make the university–industry relationship a win–win situation. [ABSTRACT FROM AUTHOR]

In order to predict the strength of a composite only based on the mechanical properties of its constituent fiber and matrix materials measured independently, 3 challenging problems must be resolved with high success rate. First, internal stresses in the fiber and matrix must be accurately evaluated. Second, efficient failure detection of the composite in terms of the internal stresses, i.e., the micromechanical strength theory, must be achieved. Last but not the least, the input data of in-situ strengths of the matrix, which can hardly be measured through experiments, must be correctly determined according to its original counterparts available independently. Each of these problems is by no means easy to deal with. This is why the prediction of composite strength is extremely difficult. The bridging model, originally established by HUANG Zheng-ming and further developed to a powerful theory, presents a systematic approach towards solving all of the 3 problems. This paper briefly summarizes the theory by focusing on some of the latest advancements. A number of further research topics are also highlighted. [ABSTRACT FROM AUTHOR]

The reversible aggregation of red blood cells (RBCs) continues to be of the basic science and clinical interest. Recently it has been reported about a specific binding between fibrinogen and unknown erythrocyte glycoprotein receptors. The aim of this study was to investigate whether the red blood cell aggregation (RBCA) include the cell-cell interaction using the membrane receptors that bind such ligands as fibrinogen or fibronectin. To test this hypothesis the RBCs were incubated with monafram - the drug of the monoclonal antibodies against glycoprotein (GP) IIb/IIIa, with the GPIIb-IIIa receptor antagonist tirofiban, epifibatide and with the fibrinogen inhibiting peptide. It has been found that the RBC incubation with monafram resulted in a marked RBCA decrease mainly in persons with high level of aggregation. Another research session has shown that RBC incubation with fibronectin was accompanied by a significant RBCA rise. The monafram addition to red cell incubation medium resulted in a significant RBCA lowering. The cell incubation with tirofiban and epifibatide issued in RBCA decrease. The similar results were obtained when RBCs were incubated with the fibrinogen inhibiting peptide. Although monafram, tirofiban, eptifibatide and the fibrinogen inhibiting peptide were related to fibrinogen function they didn't inhibit RBCA completely. Therefore, under moderate and low red blood cell aggregation the cell binding is probably related to nonspecific mode. It seems evident that the specific and nonspecific modes of red blood cell aggregate formation could co-exist. Additional theoretical and experimental investigations in this area are needed. [ABSTRACT FROM AUTHOR]

This paper attempts to estimate the ultimate strength of a laminated composite only based on its constituent properties measured independently. Three important issues involved have been systematically addressed, i.e., stress calculation for the constituent fiber and matrix materials, failure detection for the lamina and laminate upon the internal stresses in their constituents, and input data determination of the constituents from monolithic measurements. There are three important factors to influence the accuracy of the strength prediction. One is the stress concentration factor (SCF) in the matrix. Another is matrix plasticity. The third is thermal residual stresses in the constituents. It is these three factors, however, that have not been sufficiently well realized in the composite community. One can easily find out the elastic and strength parameters of a great many laminae and laminates in the current literature. Unfortunately, necessary information to determine the SCF, the matrix plasticity, and the thermal residual stresses of the composites is rare or incomplete. A useful design methodology is demonstrated in the paper. [ABSTRACT FROM AUTHOR]

The Bridging Model is a theory which can be used to predict the strength of a composite only based on its constituent properties. A remaining problem is how to define in-situ properties of the constituents. A previous work by Yao and Huang suggested that an in-situ transverse strength of the matrix can be defined by its monolithic counterpart divided by a stress concentration factor. However, the stress concentration factor therein was obtained based on an interphase model in addition to isotropic assumptions for all the constituent materials. In this paper, different imperfect interfaces and transversely isotropic fibers are employed. The stress concentration factors corresponding to these conditions are derived. Influences of various imperfect interfaces on a stress concentration factor are discussed. [ABSTRACT FROM PUBLISHER]

Abstract: A long standing and very challenging problem is to predict the ultimate strength of a fibrous laminate under arbitrary load condition only based on the mechanical properties of its constituents measured independently. Although the Bridging Model is unique for calculating the internal stresses in the constituent fiber and resin (which stands for a matrix material throughout this paper) materials subjected to any load including a temperature variation, the in situ mechanical properties of the constituents must be provided beforehand. A unidirectional (UD) composite exhibits a transverse tensile strength smaller than the tensile strength of the monolithic resin material, indicating that the in situ tensile strength of the resin in the transverse direction is different from that measured using monolithic material specimens. This is attributed to a stress concentration. The stress concentration factors (SCFs) of the resin material in a RVE (representative volume element) due to occurrence of the fiber are determined in terms of elasticity theory. The resin in situ tensile, compressive, and shear strengths in the transverse plane are obtained by the corresponding resin strengths measured independently divided by the respective SCFs, whereas the resin in situ longitudinal strengths together with all the other constituent properties are the same as their original counterparts. Using these originally provided constituent properties as input data, the Bridging Model has been applied to analyze the second World-Wide Failure Exercise (WWFE-II) problems. The model's predictions for all the problems have been compared with available experimental data. Favorable correlation has been found. [Copyright &y& Elsevier]

The stress concentration factor in the matrix of a fibrous composite reinforced with transversely isotropic fibers is determined upon constituent elastic properties as well as the fiber volume fraction available before fabrication of the composite. The matrix in situ transverse strengths are then defined from its original counterparts divided by the stress concentration factor, which are further used together with the other original constituent property parameters for calculating strengths of the composite in terms of the bridging model. The thus obtained strength envelopes of several unidirectional composites subjected to combined bi-axial loads are compared with independently measured results. Favorable correlation indicates that a composite ultimate strength can be reasonably well estimated without using any experimental data of the composite itself. The article clearly shows that an accurate prediction for a composite strength must take all of the three influencing factors, i.e. stress concentration, matrix inelasticity, and thermal residual stresses, into account. It is further demonstrated in the article that the stress concentration factor with transversely isotropic fibers involved can be sufficiently accurately approximated by a much simpler stress concentration factor formula derived upon isotropic fiber reinforcement. [ABSTRACT FROM PUBLISHER]

The bridging model was incorporated with a pseudo three-dimensional laminate theory to predict the strengths and deformation curves of a set of typical fiber‐reinforced composites under triaxial loads. The prediction was achieved using the constituent properties and geometric parameters of the composites based on the information provided by the WWFE-II’s organizers. In the present paper, the ‘blind’ predictions shown in Part A of this work are compared with the experimental results. The overall correlations between the predictions and the experiments are reasonable but somewhat conservative, especially when shear failures or large hydrostatic pressures are involved. Satisfactory improvement has been achieved when the modified maximum compressive stress failure criterion proposed previously is applied to detect fiber failure as well. Even better predictions for a number of the problems have been obtained if the constituent material properties directly taken from the organizers, rather than retrieved from the laminae data, are employed. [ABSTRACT FROM PUBLISHER]

Bridging Model is a versatile micromechanical theory, which can be used to simulate nonlinear behavior and ultimate strength of a laminated composite. The application of the Bridging Model requires input data of the in-situ mechanical properties of its constituents. A previous research has shown that the in-situ transverse strength of the matrix is equal to the pure matrix strength divided by a stress concentration factor along that direction. The stress concentration factor therein, however, was obtained based on a perfect bonding assumption between the fiber and the matrix. In this paper, a more general case is concerned. Namely, an interface layer is assumed to exist between the fiber and the matrix. Explicit expression for the stress concentration factor with an imperfect fiber and matrix interface bonding is obtained. The effect of the interface layer on the stress concentration factor is discussed. [ABSTRACT FROM AUTHOR]

A pseudo three-dimensional laminate theory is incorporated with the three-dimensional bridging model, based on micromechanics formulae, to predict failure under triaxial loads. A lamina failure is considered to occur as long as any of its constituents has failed. A laminate ultimate failure is assumed to take place when the fibres have failed or when the resin has failed in compression. In order to account for the effect of a three-dimensional compression on increasing the load-carrying ability of a resin material, a modified maximum compressive stress failure criterion is introduced. The methodology was used successfully to solve all the 12 challenging test cases of the Second World-Wide Failure Exercise. [ABSTRACT FROM AUTHOR]

Abstract: Writing software for one parallel system is a feasible though arduous task. Reusing the substantial intellectual effort so expended for programming a second system has proved much more challenging. In sequential computing algorithms textbooks and portable software are resources that enable software systems to be written that are efficiently portable across changing hardware platforms. These resources are currently lacking in the area of multi-core architectures, where a programmer seeking high performance has no comparable opportunity to build on the intellectual efforts of others. In order to address this problem we propose a bridging model aimed at capturing the most basic resource parameters of multi-core architectures. We suggest that the considerable intellectual effort needed for designing efficient algorithms for such architectures may be most fruitfully expended in designing portable algorithms, once and for all, for such a bridging model. Portable algorithms would contain efficient designs for all reasonable combinations of the basic resource parameters and input sizes, and would form the basis for implementation or compilation for particular machines. Our Multi-BSP model is a multi-level model that has explicit parameters for processor numbers, memory/cache sizes, communication costs, and synchronization costs. The lowest level corresponds to shared memory or the PRAM, acknowledging the relevance of that model for whatever limitations on memory and processor numbers it may be efficacious to emulate it. We propose parameter-aware portable algorithms that run efficiently on all relevant architectures with any number of levels and any combination of parameters. For these algorithms we define a parameter-free notion of optimality. We show that for several fundamental problems, including standard matrix multiplication, the Fast Fourier Transform, and comparison sorting, there exist optimal portable algorithms in that sense, for all combinations of machine parameters. Thus some algorithmic generality and elegance can be found in this many parameter setting. [Copyright &y& Elsevier]

The first worldwide failure exercise (WWFE-I) indicated that the bridging micromechanics model exhibited a unique feature in calculating internal thermal stresses in the constituent fiber and resin materials of a laminated composite. Once applied to laminate strength prediction, however, the model only gave moderate correlation with the experiments. In this article, a material degradation scheme and a modified ultimate failure criterion for laminates are incorporated into the bridging model to improve its predictive capacity. Pure resin inter-layers are also introduced to simulate the effect of interfaces in between the lamina plies. With these modifications, much more accurate predictions have been obtained for the majority of the exercise problems, especially for the ultimate strengths and deformations of the multi-directional laminates. The correlation of the present theory predictions with the experiments is even better than that of any other theory predictions made in the exercise. [ABSTRACT FROM AUTHOR]