The Experts below are selected from a list of 5184 Experts worldwide ranked by ideXlab platform
Y Weitsman - One of the best experts on this subject based on the ideXlab platform.
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note on the Ineffective Length of a fiber
Mechanics of Materials, 1992Co-Authors: Abraham I Beltzer, Monique Piau, Y WeitsmanAbstract:Abstract A general definition is given of the concept of Ineffective Length of a fiber, which is of use in the statistical theories of composite strength. The Ineffective Length, as formulated, may also serve as a measure of the total supporting capability of a fiber. The paper then sets forth models of an in situ fiber, deterministic or stochastic, and shows that the Ineffective Length may be by orders larger than predicted by the previous formulation. In extreme cases it may become comparable to the fiber Length. Particular examples illustrating the above models are also given.
Albert Turon - One of the best experts on this subject based on the ideXlab platform.
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A 3D Progressive Failure Model for predicting pseudo-ductility in hybrid unidirectional composite materials under fibre tensile loading
Composites Part A: Applied Science and Manufacturing, 2018Co-Authors: Jose M. Guerrero, Joan A. Mayugo, Josep Costa, Albert TuronAbstract:Abstract This paper presents a three-dimensional Progressive Failure Model based on the chain of bundles able to represent the stiffness loss in unidirectional composite materials loaded in the fibre direction. A representative volume element with a random distribution of fibres with their own radius is considered. Complete stress distributions around fibre breaks are obtained by associating a damage variable to the loss of stress transfer capability along the Ineffective Length and applying local stress concentrations. The model has been validated by comparing it against the literature results and exhibits good agreement with hybrids and non-hybrid composites. The aim of this model is to simulate the tensile response of unidirectional composite systems dominated by fibre fragmentation mechanisms using a very reduced computational effort, even for larger representative volume elements, compared to micro-mechanical finite element models.
E. V. Iarve - One of the best experts on this subject based on the ideXlab platform.
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three dimensional stress analysis and weibull statistics based strength prediction in open hole composites
Composites Part A-applied Science and Manufacturing, 2007Co-Authors: E. V. Iarve, Ran Y Kim, David MollenhauerAbstract:Abstract The critical failure volume (CFV) method is proposed. CFV is defined as a finite subvolume in a material with general nonuniform stress distribution, which has the highest probability of failure, i.e. loss of load carrying capacity. The evaluation of the probability of failure of the subvolumes is performed based on the lowest stress and thus provides an estimate of the lower bound of the probability of local failure. An algorithm for identifying this region, based on isostress surface parameterization is proposed. It is shown that in the case of material with strength following Weibull weak link statistics such a volume exists and its location and size are defined both by the stress distribution and the scatter of strength. Moreover the probability of failure predicted by using the CFV method was found to be close to that predicted by using traditional Weibull integral method and coincide with it in the case of uniform stress fields and in the limit of zero scatter of strength. Experiments performed on homogeneous epoxy resin plaques with and without holes showed that the predictions bound the experimentally measured open hole strength. The Weibull parameters used for prediction were obtained from testing only unnotched specimens of different dimensions. The effect of the hole size on tensile strength of heterogeneous materials such as quasi-isotropic carbon–epoxy composite laminates was considered next. Fiber failure was the only failure mechanism taken into account and a strain-based failure criterion was used in the form of a two parameter Weibull distribution. The stacking sequence was selected to minimize the effect of stress redistribution due to subcritical damage. Not unexpectedly an up to 30% underprediction of the strength of the laminates with small (2.54 mm diameter) holes was observed by using classical Weibull integral method as well as Weibull based CFV method. It was explained by examining the size of the CFV, which appeared to be below Rosen’s Ineffective Length estimate. The CFV method was modified to account for the presence of a limit scaling size of six Ineffective Lengths, consistent with recent Monte-Carlo simulations by Landis et al. [Landis CM, Beyerlin IJ, McMeeking RM. Micromechanical simulation of the failure of fiber reinforced composites. Mech Phys Solids 2000;48:621–48] and was able to describe the experimentally observed magnitude of the hole size effect on composite tensile strength in the examined range of 2.54–15.24 mm hole diameters.
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Strength prediction in composites with stress concentrations: classical Weibull and critical failure volume methods with micromechanical considerations
Journal of Materials Science, 2006Co-Authors: E. V. Iarve, D. Mollenhauer, T. J. Whitney, R. KimAbstract:Application of Weibull statistics to tensile strength prediction in laminated composites with open holes is revisited. Quasi-isotropic carbon fiber laminates with two stacking sequences [45/0/−45/90]_s and [0/45/90/−45]_s with three different hole sizes of 2.54, 6.35 and 12.7 mm were considered for analysis and experimental examination. The first laminate showed 20% lower strength for smaller and 10% for the larger hole sizes. A novel critical failure volume (CFV) method with minimum scaling Length constraint as well as the traditional Weibull integral method were applied. The strength prediction was based on the state of stress in the 0^° ply by taking into account the redistribution of stress due to matrix damage in the form of splitting, delamination and matrix cracking of off axis plies. The state of matrix damage precipitating failure was recorded by using X-radiography and examined by a sectioning technique. The measured extent of damage was then included in a 3D stress analysis procedure by using a mesh independent crack modeling method to account for fiber direction stress redistribution. The CFV method gave results within one standard deviation from experimentally observed strength values for both laminates and all three hole sizes. The Weibull integral method underpredicted the strength in all cases from as much as 20–30% for smaller hole sizes to 8% for the large holes. The accuracy of failure predictions using CFV is attributed to the introduction of a minimum scaling Length. This Length has a physical meaning of the width of a process zone of formation of fiber macro-crack as a result of single fiber break interaction. Direct measurement or rigorous evaluation of this parameter is, however, difficult. Consistent with referenced micromechanical studies, its value was assigned equal to six times the Rosen’s Ineffective Length.
Abraham I Beltzer - One of the best experts on this subject based on the ideXlab platform.
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note on the Ineffective Length of a fiber
Mechanics of Materials, 1992Co-Authors: Abraham I Beltzer, Monique Piau, Y WeitsmanAbstract:Abstract A general definition is given of the concept of Ineffective Length of a fiber, which is of use in the statistical theories of composite strength. The Ineffective Length, as formulated, may also serve as a measure of the total supporting capability of a fiber. The paper then sets forth models of an in situ fiber, deterministic or stochastic, and shows that the Ineffective Length may be by orders larger than predicted by the previous formulation. In extreme cases it may become comparable to the fiber Length. Particular examples illustrating the above models are also given.
Jose M. Guerrero - One of the best experts on this subject based on the ideXlab platform.
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A 3D Progressive Failure Model for predicting pseudo-ductility in hybrid unidirectional composite materials under fibre tensile loading
Composites Part A: Applied Science and Manufacturing, 2018Co-Authors: Jose M. Guerrero, Joan A. Mayugo, Josep Costa, Albert TuronAbstract:Abstract This paper presents a three-dimensional Progressive Failure Model based on the chain of bundles able to represent the stiffness loss in unidirectional composite materials loaded in the fibre direction. A representative volume element with a random distribution of fibres with their own radius is considered. Complete stress distributions around fibre breaks are obtained by associating a damage variable to the loss of stress transfer capability along the Ineffective Length and applying local stress concentrations. The model has been validated by comparing it against the literature results and exhibits good agreement with hybrids and non-hybrid composites. The aim of this model is to simulate the tensile response of unidirectional composite systems dominated by fibre fragmentation mechanisms using a very reduced computational effort, even for larger representative volume elements, compared to micro-mechanical finite element models.