Elsevier

Materials Science and Engineering: A

Volume 623, 19 January 2015, Pages 153-164
Materials Science and Engineering: A

Shear blanking test of a mechanically bonded aluminum/copper composite using experimental and numerical methods

https://doi.org/10.1016/j.msea.2014.11.045Get rights and content

Abstract

A copper clad aluminum composite sample fabricated by an Axi-symmetric Forward Spiral Composite Extrusion (AFSCE) process was analyzed using finite element models of a dedicated blanking test. The axi-symmetric composite sample was analyzed using various interfacial characterization techniques, which revealed a near flawless interface between copper and aluminum in the AFSCE sample. The dedicated blanking test (DBT) was designed to measure the bonding shear strength of the metallic composite sample. To identify the required design parameters of the test rig, a preliminary Finite Element (FE) model was developed using Abaqus finite element package. The effect of the design parameters including sample thickness, blanking clearance and fillet radii of the tools were determined to develop a large and more uniform strain along the interface and avoid bending of the metallic composite sample. The numerical results showed that the sample thickness, clearance and fillet radii have a significant effect on the measured bond shear strength and the location and magnitude of maximum strain during the blanking test. The composite copper clad aluminum bond shear strength was experimentally determined using the newly designed test rig. After that, a detailed finite element model using cohesive modeling technique was utilized to model the shear strength distribution of the metallic composite during the blanking test.

Introduction

Hybrid materials have structural and multi-functional characteristics such as thermo, electrical, magnetic and optical properties. They can supply the growing material demand for many industrial applications which require a single material with a combination of multiple properties [1], [2]. Hybrid materials are especially attractive for special purpose applications because of their unique structural properties, when a combination of weight savings and high strength is required.

Structural properties of materials are key parameters for almost any engineering application. They are also important from a handling, machining, joining and fabricating point of view. Recently, metal-based composites have been produced using different processing techniques (e.g. [3], [4]). The structural performance of such composites depends on the mechanical properties of the base materials, the stress concentration at their interface and the bonding strength of the ingredients. Yet, measuring the interface bonding strength between the parent materials could be very complex. As a result, characterization of structural properties of composites is more challenging than orthodox materials. For the case of metal-based composites with simple geometrical configuration, the interface bonding strength can be measured.

Blanking is an eminent process used in sheet metal manufacturing to produce small samples through shear failure [5], [6], [7], [8]. It has been utilised as a “small specimen test technique” [9] to determine the shear strength [10], [11], [12] and interfacial fracture toughness [13], [14], [15] of materials when there is insufficient material for testing or material saving is considered. Assuming linear correlation between shear strength and tensile strength, many researchers used the shear test to interpret yield property of materials [10], [11], [12], [16], [17], [18], [19]. The shear punch test has also been used to study the strength variations and strength gradient in Al/Ni–SiC composite samples [20], in plane stress local torsion samples [21], and in friction stir processed samples [22]. However, these tests were performed with the assumption of either homogeneous material or homogeneous shear strain distribution in the failure zone. Evaluation and interpretation of the shear strength at the interface of a composite material requires a more sophisticated approach, due to the presence of two materials at the interface. Bonding strength of aluminum clad steel sheet fabricated by cold rolling and various subsequent heat treatment processes, were evaluated using the Erichsen cupping test while it was used to assess the metal formability [23]. Bonding strength of bi-layered copper alloy and bi-layered aluminum alloy strips, fabricated using roll bonding, were tested using a peeling test according to ASTM: D903-93 (http://www.astm.org/Standards/D903.htm) [24], [25]. Fracture toughness of multilayered functionally degraded steels were numerically modeled using the three dimensional FE method [26]. However, the aforementioned standard tests and models are not suitable for a solid rod fabricated in a core-clad fashion.

A shear strength test designed based on ASTM: F1044 (http://www.astm.org/Standards/F1044.htm) was used to determine a bond shear strength of hybrid Al/Cu clad rod fabricated using equal channel angular extrusion [27]. But, the standard is mainly applicable for a test between two flat surfaces when an adhesive or cohesive bond between two calcium phosphate coated plates or two metallic coated plates is involved [28]. The standard has also been extended for a bond created by any thermo mechanical joining process such as sintering or diffusion bonding [28]. However, the standard methods used in previous works cannot obtain a reliable measurement of the shear strength for the extruded composite Al/Cu clad rods because of their cylindrical geometry.

The interfacial characteristics of the fabricated Al/Cu clad composite using axi-symmetric forward spiral composite extrusion (AFSCE) were investigated and summarized in Section 2.1. Owing to the specific requirements of the “non-standard test”, the test parameters have to be carefully analyzed to ensure a reliable bonding strength measurement. The dimensions of the test rig, most notably its die clearance, are crucial to cause a fracture of the bond interface between the two materials. Also, the effect of stress concentration and stress discontinuity at the interface because of the presence of two materials requires special care when interpreting the bonding strength; having two different materials near the interface and a sudden property change in the narrow interface region, and unavoidable stress discontinuity [29], [30] complicates the analysis.

Therefore, in order to identify the required test conditions for an accurate bonding strength measurement, a preliminary finite element model of the test rig was developed, using Abaqus finite element analysis package, to assess the test and to investigate the test rig parameters. The new FE modeling was required because welding and joining simulation reviews over the past three decades do not contain any FE study of bond shear strength for core clad composites [31], [32], [33]. The critical parameters in the numerical model were studied to develop a larger and more uniform plastic strain distribution at the interface and to minimize strain concentration in other regions. The preliminary FE analysis findings provided the required parameters to develop the large and more uniform strain along the interface also includes a blank holder, which facilitates the sample positioning and prevents bending of the sample during the dedicated blanking experiments. Having the required rig built, it was utilized to measure the composite bonding strength for an AFSCE extruded Al/Cu clad composite sample. After that a detailed FE model with cohesive interface property was carried out to model shear strength at the interface to determine the shear strength caused by the blanking test.

Section snippets

Characteristics of the interface between copper and aluminum of AFSCE processed samples

An axi-symmetric forward spiral composite extrusion (AFSCE) process has been used to fabricate hybrid rods. This process is based on the Axi-symmetric Forward Spiral Extrusion (AFSE) process which is primarily aimed for grain refinement in single materials [34], [35], [36], [37]. A variable pitch version of the AFSE extrusion die, has significantly higher efficiency compared to the original AFSE process [38] and a multi pass AFSE process has significantly improved the strength of

Finite element analysis of dedicated blanking test

It is known for a composite that the shear stress has a discontinuous distribution at the interface while the strain distribution is continuous [29], [30]. Therefore the strain is more appropriate to determine the effect of varying testing parameters and the uniformity of the strain distribution along the interfaces. Furthermore, in the case of when the copper has higher shear stress than that of the aluminum; this does not necessarily cause plastic deformation in the copper. However, stress

Conclusions

Interfacial characteristics of AFSCE processed copper clad aluminum composite samples revealed a near flawless bonding which was created mainly by a mechanical interlocking. The preliminary FE model was conducted for the composite sample to study the effect of sample thickness, clearance and fillet radius of the blanking tools on the strain distribution. Based on the carried out numerical studies, 1 mm sample thickness was identified as the most appropriate sample thickness for the dedicated

Acknowledgment

The authors acknowledge the use of the facilities and assistance of Mr. David Vowles, Dr.Flame Burgmann and Dr. Xi-Ya Fang at the Monash Centre for Electron Microscopy. This research used equipment funded by Australian Research Council Grant LE0882821. The authors would like to thank for Dr. Wenyi Yan, Mr. Louis Chiu and Mr. Nabil Chowdhury for providing advice in cohesive finite element modeling. The authors also acknowledge the support received from Monash University Postgraduate Publication

References (53)

  • M.F. Ashby et al.

    Acta Mater.

    (2003)
  • K.Y. Rhee et al.

    Mater. Sci. Eng.: A

    (2004)
  • T. Sapanathan et al.

    J. Alloy. Compd.

    (2013)
  • H. Marouani et al.

    Mater. Sci. Eng.: A

    (2008)
  • R.K. Guduru et al.

    Mater. Sci. Eng.: A

    (2005)
  • G.E. Lucas et al.

    J. Nucl. Mater.

    (1984)
  • J. Elambasseril et al.

    Compos. Part B: Eng.

    (2011)
  • J. Elambasseril et al.

    Compos. Part B: Eng.

    (2012)
  • H.-T. Lee et al.

    Mater. Sci. Eng.: A

    (2003)
  • G.L. Hankin et al.

    J. Nucl. Mater.

    (1998)
  • M.B. Toloczko et al.

    J. Nucl. Mater.

    (2002)
  • M.B. Toloczko et al.

    J. Nucl. Mater.

    (2000)
  • C.A. León et al.

    Mater. Lett.

    (2002)
  • M. Abbasi Gharacheh et al.

    Int. J. Mach. Tools Manuf.

    (2006)
  • H.D. Manesh et al.

    J. Alloy. Compd.

    (2003)
  • S.A. Hosseini et al.

    Mater. Des.

    (2011)
  • M. Eizadjou et al.

    Mater. Des.

    (2008)
  • M. Zebardast et al.

    J. Mater. Process. Technol.

    (2011)
  • A.K. Noor et al.

    Compos. Struct.

    (1989)
  • S. Khoddam et al.

    Mater. Sci. Eng.: A

    (2011)
  • S. Khoddam et al.

    Mech. Mater.

    (2011)
  • A. Farhoumand et al.

    Mater.Sci. Eng.: A

    (2013)
  • T. Sapanathan et al.

    Mater. Des.

    (2014)
  • S. Khoddam et al.

    Mater. Des.

    (2014)
  • S. Khoddam et al.

    Mater. Des.

    (2010)
  • S. Khoddam et al.

    Mater. Des.

    (2010)
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