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  • 1
    Electronic Resource
    Electronic Resource
    Springer
    Applied composite materials 2 (1995), S. 217-231 
    ISSN: 1573-4897
    Keywords: transverse crack ; cross-ply laminates ; stiffness
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract An analytical model based on the principle of minimum potential energy is developed and applied to study the effect of multiple cracks in cross-plies on the stiffness of a laminated composite. The transverse cracks are assumed to span the thickness of the cross-ply group only partially unlike in the previous studies in which they were assumed to span the entire thickness of the cross-ply group. This arrangement facilitates the study of competition between the self-similar extension of an inherent flaw within the cross-plies and the multiple parallel cracking. The numerical results for the axial stiffness as a function of both the crack density and the crack length are presented for three different composite material systems (glass/epoxy, graphite/epoxy and ceramic/ceramic) or which experimental results are available so as to validate the model.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    Springer
    Applied composite materials 1 (1994), S. 177-181 
    ISSN: 1573-4897
    Keywords: Hybrid ; Ceramic Matrix Composites ; Tape casting ; Microcracking
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract The desire to improve the transverse properties and microcracking stress of unidirectional continuous fiber reinforced ceramic matrix composites has led to development of the hybrid ceramic matrix composite (HCMC). This paper discusses the techniques we used in the fabrication of HCMC specimens used for mechanical characterization.
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    Springer
    Applied composite materials 5 (1998), S. 379-397 
    ISSN: 1573-4897
    Keywords: matrix cracking ; interface debonding ; interface friction ; strain energy release rate
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract A three-dimensional analytical model based on the principle of minimum potential energy is developed and applied to determine the stress state in a discrete fiber/matrix composite cylinder subjected to axial tensile loading in the fiber direction and containing a non-axisymmetric transverse matrix crack and an interface debond. The friction over the debonded interface is incorporated into the analysis. The strain energy release rates associated with the matrix crack and the interface debonding under the combination of the applied load and the interface frictional force are computed. The strain energy release rate criterion has been employed to evaluate the critical applied loads for the two fracture modes and to assess the competition between propagation of a matrix crack and growth of interface debonding. A parametric study has been carried out. The computed results show that the interface friction plays an important role in the failure of brittle matrix composites.
    Type of Medium: Electronic Resource
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  • 4
    Electronic Resource
    Electronic Resource
    Springer
    Journal of materials science 32 (1997), S. 2587-2594 
    ISSN: 1573-4803
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract Standard finite element wave propagation codes are useful for determining stresses caused by colliding bodies; however, their applicability to brittle materials is limited because an accurate treatment of the fracture process is difficult to model. This paper presents a method that allows traditional wave propagation codes to model low velocity, small missile impact in laminated architectural glass such as that which occurs in severe windstorms. Specifically, a method is developed to model typical fractures that occur when laminated glass is impacted by windborne debris. Computational results of concern to architectural glazing designers are presented.
    Type of Medium: Electronic Resource
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  • 5
    Electronic Resource
    Electronic Resource
    Springer
    Journal of materials science 29 (1994), S. 1185-1190 
    ISSN: 1573-4803
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract An experimental technique called bundle-debonding, has been developed for characterizing the interfacial adhesion of fibre bundles and matrix. The specimen is double-notched and contains a partially embedded fibre layer in between the notches. When a tensile load is applied at the specimen ends, the load transfer across the notch and between two pieces of matrix, occurs through the interface between a single layer of fibres and matrix. Kevlar-29 (Kelvar is a registered trademark of E.I. duPont de nemours) fibre tows were used in conjunction with a solid phenolic resin to fabricate the specimens. Experiments were conducted at various embedded lengths resulting in interfacial debond. A simple shear-lag analysis was carried out to determine the interfacial shear strength. The interfacial shear strength of Kevlar-29/phenolic resin has been determined to be 15 MPa. This technique is promising for application on several fibre/matrix systems, specially for fibres of extremely low nominal diameter, supplied as tows.
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  • 6
    Electronic Resource
    Electronic Resource
    Springer
    Journal of materials science 26 (1991), S. 655-660 
    ISSN: 1573-4803
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract An analytical model based on a consistent shear-lag theory was developed to predict the interfacial shear stress in single fibre pull-out tests. The calculations show that the stress is highly dependent on the specimen thickness and the method of testing. Data for the debond stress and the interfacial shear stress were measured for single SiC fibres embedded in a magnesium aluminium silicate (cordierite) matrix. The effect of fibre embedded length, processing schedule, and matrix toughening were investigated. For a fixed sample support configuration during testing, good agreement was obtained between the model predictions and experimental data.
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  • 7
    Electronic Resource
    Electronic Resource
    Springer
    International journal of fracture 46 (1990), S. 123-140 
    ISSN: 1573-2673
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract A micromechanics analytical model is developed for characterizing the fracture behaviour of a fibre reinforced composite laminate containing a transverse matrix crack and longitudinal debonding along 0/90 interface. Both the matrix and the fibres are considered as linear elastic. A consistent shear lag theory is used to represent the stress-displacement relations. The governing equations, a set of differential-difference equations, are solved satisfying the boundary conditions appropriate to the damage configuration by making use of an eigenvalue technique. The properties of the constituents appear in the model explicitly. Displacements and stresses in the fibres and the matrix are obtained, and the growth of damage is investigated by using the point stress criterion. The investigation includes fibre stress distribution in zero degree plies, transverse crack and debonding intitiation as functions of laminate geometry, and the effect of fibre breaks in the zero degree ply on damage growth. The predicted damage growth patterns and the corresponding critical strains agree with the finite element and experimental results.
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  • 8
    ISSN: 1573-4803
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract An experimental validation of a mechanics-based finite element model for architectural laminated glass units subjected to low velocity, two gram projectile impacts is described. The impact situation models a scenario commonly observed during severe windstorms, in which small, hard projectiles, such as roof gravel, impact windows. Controlled experiments were conducted using a calibrated air gun to propel a steel ball against simply supported rectangular laminated glass specimens. Dynamic strains on the inner glass ply were measured using foil strain gages and a high speed data acquisition system. Impact speed, interlayer thickness, glass ply thickness, and glass heat treatment conditions were varied. Dynamic strains predicted by the finite element model were in close agreement with those measured in the laboratory.
    Type of Medium: Electronic Resource
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  • 9
    Electronic Resource
    Electronic Resource
    Springer
    Journal of materials science 34 (1999), S. 4873-4882 
    ISSN: 1573-4803
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract Mechanical testing and surface fractography were used to characterize the fracture of E-glass fiber reinforced epoxy composites as a function of the silane coupling agent used. γ-Aminopropyltriethoxysilane (APS) and δ-aminobutyltriethoxysilane (ABS) were used because these have been shown to have different interfacial mobilities at multilayer coverage. The values of the properties studied generally increased from untreated 〈ABS- 〈APS-treated glass-fiber reinforced composites. Strength and critical energy release rates were more sensitive to the coupling agent used, than the modulus. The flexural strengths of untreated, ABS-, and APS-treated glass-fiber reinforced composites were 449 ± 40, 510 ± 19, and 566 ± 9 MPa (dry state); and 389 ± 23, 459 ± 7, and 510 ± 54 MPa (wet state), respectively. The critical energy release rate, Gc, as determined from a Mode I translaminar fracture toughness tests, for the untreated composites (10.5 ± 0.4 kJ/m2) was lower than that for the ABS-treated composites (14.3 ± 2.1 kJ/m2) which was lower than that for the APS-treated composites (17.1 ± 2.4 kJ/m2). Macroscopic observations showed that a larger fiber debonding area was formed in the crack tip region for the untreated glass composites, suggesting poorer bonding compared to those treated with coupling agents. Since these silanes have similar chemistry, the differences were attributed to differences in the interfacial mobility of the coupling agent layers.
    Type of Medium: Electronic Resource
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  • 10
    Electronic Resource
    Electronic Resource
    Springer
    Journal of materials science 33 (1998), S. 4775-4782 
    ISSN: 1573-4803
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract The probability of damage at the impact site in the outer glass ply of laminated glass units subjected to low velocity small missile impacts is investigated. A dynamic, non-linear finite element analysis is applied to compute the stress response on impacts. Based on the cumulative damage theory, a damage factor is introduced and related to Weibull's distribution of probability to characterize the probability of damage. In conjunction with the finite element analysis, controlled experiments are conducted to determine the material constants appearing in the damage model and Weibull's distribution of probability. A parametric study involving impact velocity, glass ply thickness and interlayer thickness is presented.
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