Longitudinal Tensile Loading Research Articles

Behavior of a Unidirectional Metal-Matrix Composite Under Thermomechanical Loading

The thermoelastoplastic behavior of a unidirectional metal matrix composite (SiC/Al) under thermomechanical loading was studied with a micromechanical model based on the average field theory. The silicon carbide fiber is considered elastic and temperature independent whereas the matrix is thermoviscoplastic and fitted into a series of power law strain hardening models. The thermoelastoplastic analysis of the composite was carried out by introducing the concept of secant properties of the matrix. Analytical predictions were compared with experimental results. Under longitudinal tensile loading the predicted stress-strain curves were in good agreement with experimental curves at three temperatures (24, 288, and 399°C). Under transverse tensile loading the secant properties of the matrix and the average stresses in the matrix and fiber (at room temperature) were obtained as a function of applied stress. The predicted stress-strain curves under transverse loading were in satisfactory agreement with experimental ones at temperatures up to 399°C. Longitudinal and transverse thermal strains as a function of temperature were also predicted and compared favorably with experimental measurements.

A comparative study of the fatigue behaviour of GRP hand lay-up and pultruded phenolic composites

This paper presents a study of the fatigue behaviour of E-glass-type fibre-reinforced phenolic composites manufactured by the pultrusion and the hand lay-up processes, with the main objective of assessing the influence of the manufacturing process on the fatigue life. For the hand lay-up process fatigue data are shown for composites with fibres aligned in the 0° longitudinal tensile loading directions, 90/0/90 orientations and 0/90/0 fibres with tensile loading applied also in the longitudinal direction. The results were obtained for two different values of frequency, stress ratio and temperature. In the pultruded specimens fatigue life data are presented at room temperature and only one value of stress ratio and frequency. The results were obtained for five sets of manufacturing parameters including a woven-type composite. With the exception of the woven pultruded specimens, which gave low fatigue strength values, the remaining types of pultruded composite have shown adequate fatigue strength values but lower than the results obtained for the longitudinally loaded 0° hand lay-up specimens. The hand-lay-up composite of the unidirectional fibre orientation (0°) have shown higher values of fatigue strength at the elevated temperature of 200°C in comparison with the room temperature values. The variations obtained in fatigue strength amongst the different types of composites are assessed through the analysis of data and also by the failure mechanisms detected by SEM observations.

Acoustic Emission Study of Failure Mechanisms in Ceramic Matrix Composite under Longitudinal Tensile Loading

Acoustic emission (AE) measurements were correlated with macroscopic stress-strain behavior and direct microscopic observations of damage mechanisms in a unidirectional ceramic matrix composite under longitudinal tensile loading. Matrix crack initiation and the onset of AE events correspond to the proportional limit of the material. Both the crack density and cumulative AE counts vary linearly up to the point of crack saturation. Thereafter follows a "strain hardening" region corresponding mainly to fiber-matrix debonding and manifested by an increase of low to moderate amplitude AE activity and leveling off of high amplitude AE signals. At higher strains, beyond the "strain hardening" region, there are two characteristic parts in the AE output, one related to further damage (possibly debonding and fiber fracture) and the other clearly related to interfacial frictional sliding. Upon unloading further AE output related to sliding is observed. AE activity of low to intermediate amplitude continues in the last stages of loading and is believed to be associated with fiber fractures.

Mechanical performance of thin-walled tubular composite elements under uniaxial loading part 1: tensile behavior

Filament wound thin-wall CFRP and GFRP composite tubes were tested under uniaxial (longitudinal) tensile loading up to failure. Elastic and strength properties as well as failure mechanisms were evaluated as related to the wall lay-up configuration. Angle-ply lay-ups of different (± θ) n orientations were compared with tubes having the same thickness but where internal and external θ plies were replaced by hoop (90) layers. Results showed that this replacement improved axial ultimate tensile strength as compared with the angle-ply reference. The three directional specimens with the hoop layers failed gradually at stress levels beyond the predicted first ply failure (FPF) as compared with angle-ply references whose behavior was highly affected and became nonlinear above FPF. Analytical prediction for elastic behavior and strength as functions of fiber orientation agreed well with experimental trends and demonstrated the advantage of three directional configuration as compared with angle-ply tube. This was attributed to the transverse stabilizing effect of the hoop layers which was manifested by a significant reduction of the Poisson ratio.

Fracture of thin-walled bodies with crack under biaxial loading

The influence of the load applied parallel to the crack on the fracture stress oriented perpendicular to the crack in thin-walled circular cylindrical shells with a longitudinal through slot has been investigated. The shells, made from titanium alloys of two brands and low-carbon steel, were subjected to static and cyclic loading by axial force and internal pressure at their various ratios. It is shown that the longitudinal tensile load in definite limits causes an increase of fracture stress and durability along with a decrease of the crack growth rate. The opposite result is obtained when the applied load is compressive. Experimental values of fracture stresses are compared with those calculated under the assumption that the crack surface energy density or the critical value of the J-integral is independent of the stress state mode.

Real-time ultrasonic monitoring of fiber-matrix debonding in ceramic-matrix composite

Real-time ultrasonic techniques were developed for monitoring damage in a unidirectional ceramic-matrix composite under longitudinal tensile loading. Specifically, shear-wave transducers producing waves polarized in the transverse to the fiber direction were used in contact with the specimen to detect the initiation and propagation of fiber—matrix debonding, and to determine the transverse shear modulus and its degradation. The ultrasonically measured transverse shear modulus and its degradation was in reasonably good agreement with a prediction based on a modified shear lag model and interpolation between available solutions for fully bonded and fully unbonded fibers.

Prediction of the Fiber-Matrix Interface Failure due to Longitudinal Tensile Loading Using Finite Element Methods

ABSTRACTA 3D-unit cell for 0/90 laminated composites has been developed to predict the composite behavior under longitudinal tensile loading condition. 3D contact element has been used to model the fiber matrix interface. Two interface conditions, namely, infinitely strong and weakly bonded, are considered in the analysis. Both large displacement and plastic strain behavior for the matrix are considered to account for the geometric and material non-linearities. Investigations were carried out at three temperatures to compare the composite response obtained from mechanical tests at those temperatures. Stress-strain behavior and the local stress distributions at the fiber as well as at the matrix are presented, and their effects on the failure of the interface are discussed in the paper. The material under investigation was SiCf/Si3N4.

Matrix cracking in a fiber-reinforced composite with slip at the fiber-matrix interface

A linear elastic analysis is presented of interfacial slip under longitudinal tensile loading in a fiber-reinforced brittle matrix composite with matrix cracks terminating and blunting at the interface. A prescribed shear stress distribution is taken in the slip region. The interfacial adhesive shear stress in the slip region which is later assumed constant is determined for different ratios of shear moduli, fiber volume fractions and slip lengths. Stress fields are obtained for a brittle matrix fiber-reinforced composite, calcium aluminosilicate glass ceramic reinforced with silicon carbide fibers (SiC/CAS), and are compared with the case when there is perfect adhesion at the interface.

Transverse Cracking and Stiffness Reduction in Cross Ply Laminates of Different Matrix Toughness

Cross ply laminates of (02,902)s configuration having AS4 graphite fibers in three epoxy resins of different toughness: 3501-6, Tactix® 556 and Tactix® 695, have been tested to determine their transverse cracking behavior and the associated mechanical response under longitudinal tensile loading. The test data are analyzed using Talreja's con tinuum damage model [1-3]. The material constants needed in the model to predict the in- plane stiffness changes are determined. The measured Poisson's ratio, which shows signifi cant change, is compared with the prediction of the model. The constants for the three materials are found to increase with the increase in their fracture toughness.

Matrix crack interaction in a fiber-reinforced brittle matrix composite

Multiple cracking in a fiber-reinforced brittle matrix composite under longitudinal tensile loading is investigated within the framework of linear elastic fracture mechanics. A perfect bond is assumed at the interface. Stress intensity factors are presented for different ratios of shear moduli, crack spacings and fiber volume fractions. Stress fields are given for a brittle matrix fiber-reinforced composite, calcium aluminosilicate glass ceramic reinforced with silicon carbide fibers (SiC/CAS). The stress fields are used to predict damage mechanisms in the composite. It is shown that crack interaction effects are significant for crack spacings that are observed in composites with good bonding at the fiber-matrix interface.

Behavior of Concrete Under Triaxial Compressive-Compressive-Tensile Stresses

Seventy-nine 10 x 10 x 55-cm prisms for triaxial compression-compression-tension specimens were tested. The tests were taken in a special device containing 2 compression testing apparatus to exert lateral compressive loadings and an ordinary universal material-testing machine to exert longitudinal tensile loading. One 3 mm fluorine-based resin sheet (Teflon) was used as a friction-reducing pad. Test results of strength and stress-strain relationships are analyzed, and formulas of concrete strength are suggested. Failure modes of specimens are also described.

Microporous materials with negative Poisson's ratios. II. Mechanisms and interpretation

For pt.I see ibid., vol.22, p.1877-82 (1989). In a previous paper the morphology of a microporous material made from expanded poly(tetrafluoroethylene) was described and results presented for its mechanical behaviour. The material was shown to be highly anisotropic and exhibited a large negative Poisson's ratio. In this paper a simple model for the microstructure is described to account for this effect. The model is based on an interconnected array of anisotropic particles that deforms so as to produce a large transverse displacement under longitudinal tensile loading. Very good agreement is found between the model and experimental results, providing an explanation for the variation of Poisson's ratio with tensile strain, in terms of changes in material morphology.

Effects of texture of zirconium alloy and multi-axial stress on iodine SCC susceptibility.

An analytical model of iodine stress corrosion cracking (SCC) of hexagonal close packed metals is developed. The SCC susceptibility is represented in the model by the elastic strain energy in the single crystals with tensile strain toward the axis of the crystal. The model incorporates the effect of crystallographic textures and multi-axial stress states. The SCC susceptibilities of the Zr and Zr alloy fuel claddings with three different textures are calculated based on the model. It is found that the stress for the tangential tensile loading of cladding is about 40% of that for longitudinal tensile loading with the same SCC susceptibility. Measurements are made on the number of microcracks on the inner surface of the Zircaloy-2 fuel claddings. These cracks are produced during the iodine SCC tests performed at 350°C under the biaxial stress state with a constant Mises' effective stress. The SCC susceptibility obtained by the proposed model was found to agree with the experimental results. The SCC susc...

Analysis and Performance of Fiber Composites

Analysis and Performance of Fiber Composites

Effects of longitudinal tensile loads on the stability of cylindrical shells under the influence of external pressure

Effects of longitudinal tensile loads on the stability of cylindrical shells under the influence of external pressure

Effect of thermal stresses on the magnitude of the breaking stress of plastic

The dependence of the short-time strength of SO-120 plastic on temperature gradients was studied. An expression was derived for calculating stresses in specimens under the influence of a one-dimensional stationary temperature field and a longitudinal tensile load. The calculated data for the temperature interval -60 to +60° C was in satisfactory agreement with experiment.