Iosipescu Shear Test Research Articles

A shear test method to measure shear strength of metallic materials and solder joints using small specimens

The asymmetrical four-point bend (AFPB) shear test, which is the subject of this paper, was originally developed by Slepetz et al. to evaluate the shear properties of large metallic specimens and polymer composites. Similar to the Iosipescu test, the AFPB test also provides a nearly pure-shear stress state with an unnotched specimen. However, since the AFPB test involves point loading as opposed to distributed surface loading in the case of the Iosipescu test, the shear force generated in this method depends on the fixture dimensions. Therefore, its use has been very limited. Recently, it was shown that this method could be used to evaluate high temperature shear properties of small ceramic composite joints. Thus, as an extension to the earlier aforementioned work, the goal of this study was to investigate the application of AFPB test method to small metallic test specimens. In this work, the Iosipescu shear test was also used to check the accuracy of results from the AFPB tests. The stress analysis of this test method by finite element modeling (FEM) will be published elsewhere.

Effect of cement modulus on the shear properties of the bone–cement interface

Shear tests of the bone–cement interface were performed in vitro using two types of bone cement, standard poly(methyl methacrylate) (PMMA) and a reduced-modulus formulation with poly(butyl methacrylate) beads in a methyl methacrylate matrix (PBMMA). Tests of shear properties were also calculated on cancellous bone and on each cement alone. The tests were done using the Iosipescu shear test method which generates a pure shear force in a zero-moment section of the specimen. With this method, shear properties can be determined at specified locations throughout the specimen. Tests were performed across the entire interface region, specifically in the middle of the region of cement–bone interdigitation and at both the bone and cement ends of that region. Ultimate shear strengths and shear moduli were calculated. The shear modulus of the PBMMA is less than 3% that of PMMA. The strength and modulus of cancellous bone had a direct relation to the apparent density of the bone, as did the strength and modulus of the bone–composite interface and the composite region. Strength and modulus were dictated by the bone at the bone–composite interface, and by the cement at the cement–composite interface. Through the composite region, the stiffer of the two materials in the composite determined the shear properties. Reduced-modulus bone coment substantially decreases the interfacial shear stresses at the bone–cement interface which should decrease the rate of resorptive bone remodelling at this interface.

Shear Deformation Properties of Extruded AlZnMg Alloys

INPG, Ge´nie Physique et Me´canique des Mate´riaux, Grenoble, France(Received November 25, 1997)(Accepted November 25, 1997)1. IntroductionMechanical characterization together with detailed studies of the microstructure and deformationmechanisms in various modes of loading are of vital importance to material modeling. In a simpletensile test of a polycrystalline metal, the force applied to the specimen acts on numerous crystallo-graphic planes, i.e. the applied stress is effectively decomposed into shear stresses on the actual slipplanes. The measured macroscopic deformation is the sum of the microscopic shear displacementswithin each grain. From this point of view, the shear stress vs. strain behavior of the material seems tobe of fundamental importance. Further, on the macro scale one can say that most metal formingoperations involve shear deformation of some sort.There are numerous ways to do shear testing. The most widely used is probably the torsion test [1].However, this method can not be applied directly to thin extrusions and rolled sheets. Among the otheroptions are specially designed tensile specimens [2], the Miyauchi shear test [3] and the Iosipescu sheartest [4]. The shear test used in the present work, however, was originally developed for testing solidpolymers [5] and later adapted for testing sheet metal samples [6,7,8]. This test offers severaladvantages. It employs rectangular test specimens that are easy to produce and which can be sampledout at different locations in the plate or sheet. Detailed information on the shear anisotropy, sheardeformation rates and microstructural gradients are easily obtained. Further it is possible to reach veryhigh strains without fracture or necking and to carry out stress reversal tests, strain path changes, strainrate changes etc.In earlier work on the present high strength AlZnMg alloys, both tensile testing and texturemeasurements have been employed [9]. These investigations revealed a strong directional dependencein the mechanical properties caused by crystallographic texture.2. Experimental ProcedureThe MaterialThe present investigations were carried out on flat extrusions (5mm 3 150mm) of the alloys AA7108and AA7030 with chemical compositions shown in Table 1. The plates were received from the RaufossHydro Automotive Research Centre AS in the as extruded condition.

Effect of Load Distribution and Placement in the Iosipescu Shear Test

The presence of the v-notch has tended to be the focus of stress analyses performed in conjunction with the Iosipescu shear test. However, load placement and distribution relative to the notch cross section can have an effect on the shear stress distribution. In addition, the axial normal and transverse normal stresses do not necessarily vanish between the notches. Loading effects are examined in the present paper by considering an exact elasticity solution for a straight beam (no v-notch) with Iosipescu type loading. Numerical results indicate that load placement and distribution effects depend on material properties.

The behavior of ceramic-matrix composites under thermo-mechanical cyclic conditions

The thermo-mechanical behavior of ceramic-matrix composites is analyzed in the framework of continuum damage mechanics through the introduction of internal variables. The choice of these variables is based upon the study of a micromechanical model describing the degradation mechanisms that have been observed in the material. The model identification is performed by studying two tension tests. The model is then used to predict the result of a Iosipescu shear test. An extension for cyclic and thermal loadings is presented.

Shear Strength of a Thermal Barrier Coating Parallel to the Bond Coat

The static and low cycle fatigue strength of an air plasma sprayed (APS) partially stabilized zirconia thermal barrier coating (TBC) is experimentally evaluated. The shear testing utilized the Iosipescu shear test arrangement. Testing was performed parallel to the TBC-substrate interface. The TBC testing required an innovative use of steel extensions with the TBC bonded between the steel extensions to form the standard losipescu specimen shape. The test method appears to have been successful. Fracture of the TBC was initiated in shear, although unconstrained specimen fractures propagated at the TBC-bond coat interface. The use of side grooves on the TBC was successful in keeping the failure in the gage section and did not appear to affect the shear strength values that were measured. Low cycle fatigue failures were obtained at high stress levels approaching the ultimate strength of the TBC. The static and fatigue strengths do not appear to be markedly different from tensile properties for comparable TBC material.

Experimental Assessment of Four Composite Material Shear Test Methods

Abstract Four ASTM standard shear test methods for characterizing composite materials were experimentally investigated: the short beam shear (ASTM D 2344), Iosipescu shear (ASTM D 5379), axial tension of a [±45]ns laminate (ASTM D 3518), and two-rail shear (ASTM D 4255). Six composite material systems were utilized: two thermoset matrix composites; S2 glass/3501-6 epoxy and AS4 carbon/3501-6 epoxy; and four thermoplastic matrix composites, S2 glass/polyetherketoneketone (PEKK), AS4 carbon/PEKK, E-glass/J2 polyamide and AS4 carbon/J2 polyamide. The results obtained for both shear strength and shear modulus indicate that the various methods each have limitations and inherent inaccuracies, with no one method being clearly superior to the others in all aspects. However, the Iosipescu shear test method does exhibit a number of particularly favorable characteristics.

Discussion of the article, “experimental strain analysis of the Iosipescu shear test specimen”

Discussion of the article, “experimental strain analysis of the Iosipescu shear test specimen”

Optimization of the adhesive joint Iosipescu specimen for pure shear test

This paper reviews some of the difficulties encountered in achieving a uniform stress distribution within the adhesive layer of bonded Iosipescu shear test specimens. The asymptotic singular stress field at the terminus of a skewed bimaterial interface, intersecting the straight free surface of the wedge, has been studied macroscopically and microscopically using the finite element method (FEM) and the finite element iterative method (FEIM). Different mechanical properties of the adhesives and adherends, and various skewed interface angles have been considered in this study. A critical skewed interface angle, αc=126°, has been found beyond which the interfacial stress singularity vanishes. This critical angle is independent of the elastic properties of the adhesives and adherends. Based on the results obtained in the present investigation, in conjunction with recently reported research on sharp notches [7, 21–23], an optimized adhesive joint Iosipescu specimen geometry is proposed. This specimen should be capable of generating a uniform shear stress state within its adhesive layer under pure shear loading conditions.

Material Characterization of Pultruded Laminates and Shapes

This paper discusses the material characterization of wide flange pultruded structural shapes (E-glass, Vinylester). The material was subjected to three loading conditions: tension, shear, and bending. Coupon samples were obtained from web and flanges of the I-section for tension and shear tests. Tensile properties were obtained from rectangular coupons with end tabs loaded in tension to failure. Shear properties were obtained from two different test methods: Iosipescu shear test method and torsion of rectangular samples. Experimentally determined material properties were compared to analytical predictions based on micro and macromechanics. Micromechanical models are used for the prediction of individual laminae (roving layers, continuous strand mat, nexus veils) properties. Classical lamination theory (CLT) is then used to predict the laminate properties. In addition, I-beams were tested in bending to evaluate their response and the experimental results were compared to predictions using Mechanics of Laminated Beams (MLB) approach. Results indicate a good correlation between experimental data and theoretical predictions, showing that the properties of pultruded composites can be predicted with sufficient accuracy. The superiority of the torsion test for determination of in-plane shear stiffness is demonstrated.

Robust Design of the Iosipescu Shear Test Specimen for Composites

Abstract For the purpose of improving the accuracy of the Iosipescu shear test method, researchers have been interested in analyzing the uniformity of shear stress distribution along the notched cross section for different design configurations of specimens made of various materials. But a one-factor-at-a-time approach cannot lead to a full understanding of the shearing behavior. The statistical design of experiments based on finite element models is employed here to characterize impacts of main effects and interactions among various design factors on the uniformity of shear stress distribution along the notched cross section for two kinds of unidirectional laminae with different orthotropy: Boron/Al (boron-fiber-reinforced aluminum) and Gl/Epoxy (glass-fiber-reinforced epoxy). It is shown that (a) the notch radius and height of a specimen are significant factors, (b) the notch angle is also significant, and 90° is better than 110° in reducing the variation of shear stress distribution, and (c) some two-factor interactions are influential.

Iosipescu Shear Test of Composite Joint Specimens in Tensile Loading

The stress field arising in tensile loading of the Iosipescu shear test is analyzed by means of finite element method. In a parametric study on a composite laminates-adhesive joint, the tensile loading method is shown more effective in creating a pure shear stress field with negligible normal stresses in the notched area than the conventional compressive loading method, although the maximum shear stress is marginally higher for the former method than the latter.

On the machining of fiber reinforced plastic (FRP) composite laminates

With the increasing use of fiber reinforced plastic (FRP) composites outside the defense, space and aerospace industries, namely, civilian industries, machining of these materials is assuming a significant role. Unit cost rather than solely performance at any cost will be the consideration for the implementation of FRP composites to consumer industries. The current knowledge of machining FRP composites, unfortunately, is inadequate for its optimum utilization in many applications. This paper presents some observations made on the orthogonal machining of unidirectional carbon fiber reinforced plastic (UD-CFRP) laminates with different fiber orientations. Iosipescu shear test was adopted to evaluate the inplane shear strength of varied fiber angle test specimens. A model for predicting the cutting forces and the dependence of cutting direction on machinability requirements is presented.

Determination of Shear Properties for RP Pultruded Composites

A complete understanding of the behavior of a structural system comprising RP components necessitates the determination of material properties for these components. Properties of interest include tensile, compressive, shear and bending stiffness and strength. This study focuses on the identification of a reliable test method for the determination of in-plane shear modulus and strength. Iosipescu shear tests and torsion tests were conducted on coupon samples. Results indicate that the torsion test is an easier and reliable method for the determination of shear modulus whereas the Iosipescu test should be used for the determination of shear strength.

Experimental and Analytical Studies of Failure Modes in Iosipescu Specimens under Biaxial Loadings

This study is concerned with an extension of the traditional Iosipescu shear test to in-plane biaxial stress applications. A Biaxial Stress Test Fixture, which is based upon the original Iosipescu shear test and the Arcan in-plane stress method, is used to characterize mixed-mode failure phenomena in both isotropic (PMMA) and orthotropic (teak) Iosipescu specimens under externally applied biaxial loads. The fixture is used for generating failure data for a wide range of biaxial (dominated by shear) loading conditions. Finite element methods are used to evaluate the stress state at the notch tips (as a function of the notch-tip radius) of biaxially loaded Iosipescu specimens. In addition, a simplistic analytical approach has been applied to estimate the notch-tip stresses at the onset of failure. A high quality failure envelope has been generated for teak under a combination of shear and transverse tensile loading conditions. Results from the finite element analysis show that an absolute numerical evaluation of the stress distribution at the notch tips can be misleading if a linear-elastic material behavior is assumed. However, the analytical approach, which assumes a uniform stress state along the notch-root axis, is found to more accurately represent the notch-tip stresses. Preliminary results strongly indicate the potential of the Biaxial Iosipescu method as a reliable test procedure for biaxial stress applications.

Experimental determination of TSAI failure tensorial terms Fij for unidirectional composite materials

Composite materials are being used more and more for components of large thickness. For this kind of component, two-dimensional failure criteria do not seem to be adequate to describe the mechanical behaviour of these structures. This paper presents an experimental determination (without reference to damage mechanisms) of the different terms of the strength tensors of a three-dimensional polynomial failure criterion for two different composite materials (graphite/epoxy T300/914 and glass/epoxy M10). The considered third dimension leads to some experimental difficulties in the determination of out-of-plane parameters F 3, F 33, F 44, and F ij. A new testing fixture (double compression fixture), new experimental conditions (Iosipescu shear test) and a new specimen shape (through-the-thickness tension test) are proposed to solve these problems. Finally, the two strength tensors F i and F ij are totally determined to meet the requirements of engineers and designers.

An Improved Iosipescu Shear Test Fixture

A new Iosipescu shear test fixture design that can be used to perform the test procedure outlined in Test Method for Shear Properties of Composite Materials by the V-Notched Beam Method (ASTM D 5379) was designed, fabricated, and tested. The new fixture solves the often reported problems of specimen twisting, variability of results, and differences in measured shear modulus between [0]16, [0/90]4s, and [90]16 laminates. Lateral instability of the Iosipescu specimen is explored as the main agent causing the undesirable effects observed with the previous fixture design.

Some aspects of the Iosipescu shear test

The influence of the notch angle employed in an Iosipescu test is considered. It is shown that (a) choosing a notch angle smaller than 102.6 degrees induces a singular stress state, and (b) offsetting the notch always induces a stress singularity.

Effect of Fiber Treatment on the In-plane Shear Properties of Composite Materials

Abstract The effect of the fiber surface treatment on composite material shear behavior is evaluated. The Iosipescu shear test is employed to measure the in-plane shear properties of unidirectional AU4- and AS4-BMI/PES, as well as IM8-BMI/PES, with 50%, 100% and 400% fiber surface treatment. In addition, a meso-indentation technique is employed to assess the effect of degrees of surface treatment on interfacial shear strengths. It was found that the in-plane shear properties of AU4- and AS4-BMI/PES laminates are essentially the same. The in-plane shear properties of IM8-BMI/PES laminates with 50%, 100% and 400% fiber surface treatment are approximately the same. Meso-indentation results confirm the Iosipescu shear strengths obtained.

Accurate and Precise Fabrication of Iosipescu Shear Test Specimens

Abstract The experimental measurement of the shear modulus and shear strength has been of special interest to the materials and composites community for a number years. In recent years, the Iosipescu shear test method has become popular and widely used. The most widely used test fixture is the Modified Wyoming test fixture which requires a specific and accurately fabricated specimen. To date, the methodology to fabricate and inspect these specimens has been left to the discretion of the individual investigators. This technical note presents a suggested methodology for the accurate and precise fabrication of Iosipescu shear test specimens. Dimensional data and the associated error from specimens fabricated are presented as verification of the methodology.