In-plane Tensile Loading Research Articles

Effect of crossing warp arrangements on delamination resistance of 3D woven composite T-joints under in-plane tensile loading

An experimental study for investigating the delamination behaviour of 3D woven composite T-joints with weave variations and optimising weave architectures is carried out. This study involves 10 types of crossing warp architectures at the junction. Quasi-static tensile load is applied to two flanges of 3D woven composite T-joints to evaluate the in-plane mechanical performance. The crossing warp architecture effectively improves the in-plane mechanical performance. Results indicate a significant influence of crossing warp arrangements on failure modes of the 3D woven composite T-joints. The use of internal crossing warp architectures leads to severe delamination in the 3D woven composite T-joints while the composite T-joints with 3D woven external crossing warps primarily fail due to the debonding of fibres and matrix and fibre breakage. The optimal weave architecture for 3D woven composite T-joints is confirmed by analysing the in-plane mechanical behaviour with different crossing warp arrangements and proportions. Regardless of the crossing warp proportions, the external crossing warp architectures outperformed their internal counterparts in resisting delamination, resulting in a maximum increase of 68.75 %, 30.04 % and 116.81 % in modulus, strength and failure strain respectively.

Multi-scale characterization of self-sensing fiber reinforced composites

The piezoresistive properties of fiber-based embedded sensors across tow, fabric, and laminate scales offer opportunities for their efficient application in fiber reinforced polymer composite (FRPC) structures. This study involves the multi-scale characterization of rGO-coated glass fiber tows, fabric, and laminates produced via vacuum assisted resin transfer molding (VARTM). The study demonstrates how fiber type, areal weight, and architecture affect piezoresistivity in rGO-coated glass fiber-based sensors subjected to in-plane tensile loading. In this study, rGO-coated glass fiber tows, with three linear densities (138, 1200, 1232 TEX), were examined. Fabric-level sensors, including plain weave (PW), and quadriaxial (QUAD), with areal densities of 200, 600, and 807 g/m2 were also studied. For comparison, laminates using UD carbon fabrics (300 g/m2) were employed as embedded piezoresistive sensors in the glass fiber-based laminates. It has been shown that rGO-coated sensors with lower areal weights outperformed all other sensor types in terms of their piezoresistive characteristics. This study suggests that piezoresistive sensors offer significant potential for use in load-bearing structural applications which can be further enhanced by investigating their lower scales.

Design of functionally graded material to reduce stress concentration around semicircular notches for Inplane tensile and bending loads

Design of functionally graded material to reduce stress concentration around semicircular notches for Inplane tensile and bending loads

Thermal Postbuckling Analysis of Thin Uniform Square Plates On Winkler Foundation - Effect of Use of Green’s Strain-Displacement Relations

A new simple formulation is developed in this paper, to predict the realistic thermal postbuckling behavior of the square plates, on Winkler foundation. If the plate is subjected to a uniform temperature rise, and also undergoes large deflections, mechanical equivalent inplane compressive, and tensile loads are developed, with the condition of the inplane immovability of the normal edge displacements of the plate. The nature of the distribution of these inplane compressive and tensile loads are similar, but have different magnitudes, which act along the x- and y- directions of the plate. The use of the Green’s nonlinear strain-displacements relations, which do not impose any restriction on the magnitude of the large deflections, to predict the realistic thermal postbuckling loads. The thermal postbuckling results of the plates obtained from this formulation, are validated indirectly, as the corresponding results are not available in the literature, with those of the columns without the elastic foundation. For the non-zero values of the foundation parameter, the present numerical results of the plates, with respect to the central deflection, show the proper physical trends of the nonlinearity, and demonstrate the simplicity of the present formulation.

Woven geotextile permeability under uniaxial and laterally constrained conditions

Woven slit-film geotextiles are often subjected to in-plane tensile loads in engineering applications, which may alter relevant permeability properties. The fractal model of the permeability coefficient in woven geotextiles is extended to predict the permeability coefficient of geotextiles subjected to uniaxial and laterally constrained uniaxial tensile strains. Based on the observation and summary of the variation of the pore size distribution pattern with tensile strain, the pore unit model is introduced. The model is expressed as the functions of the fractal dimension, pore size characteristics, physical parameters and weft strain. A clamping device capable of applying uniaxial tension and laterally constrained uniaxial tension to geotextiles is invented. The validation of the model is verified using the vertical permeability coefficient test and the digital image analysis method on two selected woven geotextile samples. It is shown that the permeability coefficient increased with increasing uniaxial tensile strain. Furthermore, the experimental values tended to change more significantly under laterally constrained uniaxial strain conditions for thinner geotextiles approaching breaking strain and thicker geotextiles. The improved model can accurately predict the values and increasing rate of the permeability coefficient of woven geotextiles subjected to uniaxial and laterally constrained uniaxial tensile strains.

Internal Stress Distribution in Suspension Plasma Sprayed Thermal Barrier Coating Subjected to in-plane Tensile Loading

Internal Stress Distribution in Suspension Plasma Sprayed Thermal Barrier Coating Subjected to in-plane Tensile Loading

Strain-rate Dependence of Electrically Modified Unidirectional Carbon/epoxy Laminates Under In-plane Tensile Loading

Strain-rate Dependence of Electrically Modified Unidirectional Carbon/epoxy Laminates Under In-plane Tensile Loading

A study on the damage tolerance of durable redundant composite sandwich joints

A patented Durable Redundant Joint (DRJ) concept featuring multiple adhesive load-paths, via a novel composite preform insert, is being considered for joining composite sandwich panel segments. Applications are wide ranging from spacecraft bus structure to launch vehicle primary structure (i.e. interstage cylinders and payload fairings). Numerical and experimental investigations were performed to assess the DRJ’s performance. A fracture-based approach was used to evaluate this design. Ply-level mechanical properties for the material systems were generated, and a double cantilever beam coupon was designed and tested to estimate the Mode I critical energy release rate for the interface between two different composite prepreg material systems. The DRJ was tested and compared to testing of the more conventional splice joint (CSJ) design. Polytetrafluoroethylene (PTFE) inserts were used at the free edges of the joints to simulate debonds between the doubler and facesheet laminates. The DRJ coupons reached 32% greater in-plane tensile failure load compared to the CSJ coupons. Furthermore, the predicted increased strength for the DRJ design compared to the CSJ design was in remarkably good agreement with test data. Using the insight gained from these studies, three design attributes were investigated relative to increasing damage tolerance characteristics of the DRJ: (1) Insert stiffness, (2) Relative length between the doubler and the insert, and (3) The use of tapers at the ends of doublers.

A three-dimensional micromechanical model for simulating ply crack formation in laminates under in-plane tensile loading

Micromechanical models were established to simulate ply cracking in [0/90/0] laminates under tension. A new user-defined material model was developed within a finite element framework to capture inelastic deformation of the matrix and local cavitation-induced and ductile failure. A damage model was used to capture corresponding post-peak behaviour. Representative volume elements (RVEs) of laminates were generated, where the fiber and matrix constituents were explicitly represented in the 90° ply. The experimentally verified simulations revealed local matrix failure onset was governed by brittle cavitation, while subsequent microcracking was influenced by local ductile failure. The model accurately captured the delay in first full ply crack formation for laminates with thinner plies. The role of thermal residual stress, ply constraints, and fiber volume fraction on ply crack formation were investigated. The associated effective energy release rate was predicted and can be used for predicting ply crack multiplication in meso- or macro-scale models.

A parametric study on the failure strength of multi-bolt composite repairs with different configurations

In this work, a numerical method based on the finite fracture mechanics is presented for predicting the failure behaviour of multi-bolt composite repairs with different configurations. This numerical method is verified by comparing the experimentally obtained strain distribution, failure strength and failure mode of multi-bolt composite repairs with circular, elliptical and oblong cutouts with the numerical ones. Based on the verified numerical method, a detailed parametric study on the critical parameters affecting the failure strength of multi-bolt composite repairs is carried out, including the load transfer ratio, the specimen width, the fillet size, the bolt diameter, the missing bolts and the patch thickness. It is found that the failure strength of the damage hole is less affected by the critical stress intensity factor and more affected by the load transfer ratio. However, a converse trend exhibits for the failure strength of the bolt hole. When the size of the damaged area is constant, the width of the repaired structures has a negligible effect on the failure strength. For the countersunk single-shearing bolt, bolt diameter has weak effects on the bolt stiffness, the load transfer ratio and the failure strength of damage hole. While it has an obvious effect on the failure strength of the bolt hole. In addition, when the repaired structures are subjected to in-plane tensile load, the bolts with smaller load transfer ratios have weak contributions to the failure strength of the repairs. The obtained conclusions can provide useful guidance for the optimal design and improved repairing efficiency of the multi-bolt composite repairs with different configurations.

Mechanical behavior and failure mechanism of the 3D angle interlocking woven reinforced aluminum matrix composites under in-plane tensile loading

3D angle interlocking fabric reinforced aluminum composites were prepared by the vacuum assisted pressure infiltration method. The mechanical properties and damage behavior of the composites subjected to in-plane tensile loading were investigated using the micromechanical finite element simulation and experimental method. The results show that the tensile stress-strain curve from simulation is in agreement with the testing curves, where the calculation errors of the initial modulus, ultimate strength and fracture strain in warp (weft) direction are 3.96%(1.11%), 1.40%(6.86%) and −5.49%(3.73%), respectively. Under the warp directional tension condition, the interface on warp yarns and the adjoint matrix alloy damage successively. With the increase of tensile strain, these damage zones accumulate and interact with each other, leading to the failure of interface, matrix and weft yarns in sequence. The fracture of warp yarns in the terminate stage induces the ultimate failure of the composites. During the weft directional tensile process, the interface on warp yarns and the thin matrix alloy between yarns damage and fail firstly. The transverse fracture of warp yarns occurs in the middle stage of tensile deformation. The axial fracture of weft yarns, which sustain the loading stress at the end of deformation process, is the main failure mechanism of the composites under weft directional tensile condition. The tensile modulus and strength in weft direction are 81.8% and 56.5% times than those in warp direction, owing to the lower volume fraction of weft yarns in the 3D angle interlocking fabric.

Progressive failure analysis of laminated plate containing elliptical cutout

PurposeThe prediction of accurate failure strength and a composite laminate failure load is of paramount importance for reliable design. The progressive failure analysis helps to predict the ultimate failure strength of the laminate, which is more than the first ply failure (FPF) strength. The presence of a hole in the laminate plate results in stress concentration, which affects the failure strength. The purpose of the current work is to analyze the stress variation and progressive failure of a symmetric laminated plate containing elliptical cutouts under in-plane tensile loading. The effect of various parameters on FPF and last ply failure (LPF) strength is studied.Design/methodology/approachThe ply-by-ply stresses around elliptical cutouts are obtained analytically using Muskhelishvili's complex variable formulation. To predict the progressive failure, Tsai–Hill (T-H) and Tsai–Wu (T-W) failure criteria are used, and depending on the mode of failure, lamina modulus is degraded.FindingsThe study has revealed that fiber orientation and stacking sequence for given loading have the most significant effect on the laminate's failure strength.Originality/valueComplex variable method and conformal mapping are simple and proficient for studying failure analysis of a laminated plate with elliptical cutout.

Edge strength of core drilled and waterjet cut holes in architectural glass

In structural glass design, an often-applied connection is a bolted connection subjected to in-plane tensile loads. Traditionally, the hole in the glass pane is manufactured by core drilling and conical edge finishing. An alternative method is by waterjet cutting the holes, resulting in cylindrically shaped holes. This research compares the edge strength of core drilled and waterjet cut holes. It focuses on in-plane tensile tests and consists of an experimental part in combination with a numerical part. In the in-plane tensile tests, peak stresses occur perpendicular to the load direction. These stresses are found to be higher for waterjet cut holes (+ 13%) compared to core drilled holes. As a result, the characteristic ultimate load is lower for waterjet cut holes (− 16%). Furthermore, the influence of thermally toughening the glass is found to be more favourable for the characteristic ultimate load of specimens containing core drilled holes than it is for waterjet cut holes. Next to that, it was found that the ultimate load linearly increases with the panel thickness. Eccentric loading, caused by insufficient bushing material or rotation of the bolt, only slightly decreases the ultimate load, provided that no hard contact between bolt and glass occurs. In addition, coaxial double ring tests were performed in the hole area, showing that waterjet cut holes result in larger stresses near the hole edge than core drilled holes. Furthermore, waterjet cut holes are found not to be perfectly round, while drilled holes are. This un-roundness negatively influences the ultimate load and the stresses in the glass; the larger the extent of un-roundness, the higher the stresses and the lower the ultimate load. Also, the orientation of the un-round hole is of influence on the stresses and ultimate load for the tensile test. It is concluded that waterjet cut holes result in lower characteristic ultimate loads and higher stresses. Due to the different edge finishing, the ultimate load still is lower compared to core drilled holes, even if the waterjet cut holes are perfectly round.

On the stochastic first-ply failure analysis of laminated composite plates under in-plane tensile loading

This paper highlights the amount of risk taken when a deterministic approach is used in designing composite structures without consideration of stochastic effects. The study treats all material and geometric parameters of the composite laminated plates under investigation as stochastic. Monte Carlo simulation is employed to investigate the stochastic effects of material properties, ply thickness, and ply orientation on the failure of laminated composite plates under static loads. Classical lamination theory is used to calculate the strength ratios using maximum stress, Tsai-Hill, and Tsai-Wu failure criteria for plates of three different materials in various stacking sequences. Variation in the failure ply distributions are shown to increase with coefficient of variation of the input variables. A positive linear trend between the coefficients of variation of the strength ratio and input variables is found, whose slope increases as randomness is considered for more input variables. Probability of failure and failure ply distributions are shown to be heavily dependent on the combination of laminate stacking sequence, material, and failure probability. In particular, while the empirical failure probability for cross-ply laminates is highest for the ply predicted by a deterministic analysis, this probability decreases rapidly with increasing variation in input parameters. Further, the failure of unexpected plies for cross-ply laminates is shown to be related to the stiffness ratios of the plies. The general significance of considering ply thickness and ultimate strength as random variables is also demonstrated, as well as the significance of randomness in ply orientation for balanced and angle ply laminates.

Theoretical prediction of the punching shear strength of concrete flat slabs under in-plane tensile forces

RC slabs can be subjected simultaneously to transverse loads and in-plane tensile forces, as it happens in top slabs of continuous box girder bridges decks, in the regions of negative moments, or in flat slabs subjected to horizontal loads, produced by wind or earth pressure. Tensile forces can reduce the shear punching capacity of slabs. However, few studies have been carried out to quantify this effect. With this purpose, a mechanical model has been developed to capture the influence of in-plane tensile forces on the punching shear strength and verified with punching tests under different in-plane tensile load levels. The model, presented in this paper, consists of an extension of the Punching shear Compression Chord Capacity Model to account for the effects of tensile forces on the resisting actions. A linear reduction of the punching shear strength as a function of the external load applied has been obtained for moderate tensile forces, whereas high level of tensile forces may produce premature yielding of the reinforcement and further reduction of the punching shear strength. The proposed model accurately captures the available test results, including the effects of the premature yielding of reinforcement when the tensile force produces concrete cracking. In addition, predictions of punching-shear-tensile tests available in the literature were made with different theoretical models included in design codes, which yielded in general conservative results and showed high scatter.

On rotational instability within the nonlinear six-parameter shell theory

Within the six-parameter nonlinear shell theory we analyzed the in-plane rotational instability which occurs under in-plane tensile loading. For plane deformations the considered shell model coincides up to notations with the geometrically nonlinear Cosserat continuum under plane stress conditions. So we considered here both large translations and rotations. The constitutive relations contain some additional micropolar parameters with so-called coupling factor that relates Cosserat shear modulus with the Cauchy shear modulus. The discussed instability relates to the bifurcation from the static solution without rotations to solution with non-zero rotations. So we call it rotational instability. We present an elementary discrete model which captures the rotational instability phenomenon and the results of numerical analysis within the shell model. The dependence of the bifurcation condition on the micropolar material parameters is discussed.

Buckling and free vibration of a side-cracked Mindlin plate under axial in-plane load

In this paper, the buckling and free vibration of a Mindlin plate with a side crack are presented considering a uniaxial in-plane compressive or tensile load. The side crack is through the thickness of the plate. In the Ritz method, a series of corner functions are incorporated into the admissible functions which consist of the modified characteristic functions. With this treatment, one can describe the singularity in stress near the tip of the crack as well as the discontinuities in both displacement and bending rotations across the crack. The buckling loads and natural frequencies are solved through eigenvalue problems considering the existence of the crack. The effects of location, length and orientation of the crack on the buckling and free vibration of the loaded plate are demonstrated. The coupling effect of the crack and the in-plane load on the vibrational characteristics of the plate is analyzed with varying parameters. It is shown that the influences of the tensile and compressive preloads are enhanced by the crack, and the tensile preload can cause the low-order frequency to increase with the growing crack.

Stress analysis of composite plate with cutout of various shape

Composite plate found numerous applications in various structures due to its superior properties like high stiffness to weight and strength to weight ratio. Generally, cutouts in these structural elements are unavoidable for many purposes like access to internal parts, ventilation and sometimes to prevent resonance. These geometrical discontinuities in the form of cutouts may be of different shapes and arise nonuniform stress in the plate. Therefore, it becomes necessary to analyse stress concentration factor near cutouts and effect of shape of cutouts on axial deformation and stress distribution for better safety and stability of structure. In the present investigation a Carbon/epoxy composite plate with various shape of cutout subjected to in-plane tensile loading is considered. Finite element based plane stress analysis is used for mathematical modeling. A program for the present analysis is developed in MATLAB. Variation of in-plane displacement and stress concentration factor (SCF) with various shape of cutout is determined. The effect of the geometry of hole on the stress distribution around the hole is also studied. The results of various analyses have been presented with the help of tables, graphs, and nodal plots.

CNT Reinforced Laminated Composite under In-Plane Tensile Loading: A Finite Element Study

The present study is mainly aimed at investigating the distribution of in-plane stresses of a rectangular plate under localized uniform in-plane tensile loading through finite element analysis. The configuration used in the analysis is analogous to the case of premature failure of stiffened panel due to the termination of a stiffener in aircraft wing structure. In this current work, three different types of materials namely, isotropic, plain woven and transversely isotropic materials are being considered. Aluminium is taken as isotropic; high strength carbon/epoxy is being assigned as plain woven composite and carbon nanotube based hybrid composite is used as transversely isotropic material, due to their wide range of applications in aircraft structures. The effect of different materials on overall axial, transverse and shear stress distributions at different layers of the stiffened composite panels are demonstrated using finite element analyses. Further, the variations of these stresses along axial and transverse directions are also compared for different materials. It can be concluded from the present study that the peak stress developed near the load application zone should be incorporated in the design criteria of such plates to avoid failure.

Combining in-situ synchrotron X-ray microtomography and acoustic emission to characterize damage evolution in ceramic matrix composites

In-situ synchrotron X-ray microtomography and acoustic emission (AE) were combined to study the behavior of ceramic matrix composite laminates subjected to in-plane tensile or flexural loading at room temperature. A detailed characterization of the initiation and progression of two key damage modes (matrix cracking and fiber breaks) is obtained from microtomography, and the relationship between damage and AE is directly observed. A graphical representation of AE data, which has potential for real-time use, is employed to reveal differences in damage progression due to fiber architecture or loading mode. In addition, strong empirical relationships are observed between matrix crack area and AE energy, as well as between fiber breaks and number of AE events.