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Optimization of Tab Geometry to Minimize Longitudinal Stress Concentration During Tensile Testing of Unidirectional CFRP



A uniaxial tensile test is a useful method for determination of material properties, especially longitudinal tensile strength. To accurately derive the longitudinal tensile strength, it is desired that the specimen fails in in the gauge section defined here as ‘working zone’. Unidirectional (UD) composites require use of end tabs during this tensile testing to avoid damage to the specimen due to grip serrations. The grip pressure, along with sudden geometry change at the edge of end tabs leads to longitudinal stress concentrations. The conventionally used rectangular and tapered end tabs suffer from these longitudinal stress concentrations under the edge of end tabs, causing premature failure of specimen outside of the working zone. In the present paper, a simulation study is performed for comparison of conventional end tabs with hybrid specimen geometry [1] and a novel arrow-shaped end tab geometry to determine the effect of end tab geometry on longitudinal stress concentrations. The study is focused on high modulus carbon fibre HS40/epoxy UD (0°) composite. The numerical model replicates the actual set-up for uniaxial tensile testing, including contact interactions between testing machine components. The simulation results are used to further optimise the geometry and provide recommendations to eliminate or minimise longitudinal stress concentrations.


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G. Czél, M. Jalalvand, and M. R. Wisnom, “Hybrid specimens eliminating stress concentrations

in tensile and compressive testing of unidirectional composites,” Compos. Part A Appl. Sci.

Manuf., vol. 91, pp. 436–447, 2016, doi: 10.1016/j.compositesa.2016.07.021.

АSTM Standard, “ASTM 2290-12 Standard Test Method for Apparent Hoop Tensile Strength

of Plastic or Reinforced,” ASTM B. Stand., pp. 1–8, 2016.

M. E. Cunningham, S. V Schoultz, and J. M. Toth, “Effect of End-Tab Design on Tension

Specimen Stress Concentrations,” in Recent Advances in Composites in the United States and

Japan, J. R. Vinson and M. Taya, Eds. West Conshohocken, PA: ASTM International, 1985,

pp. 253–262.

I. De Baere, W. Van Paepegem, and J. Degrieck, “On the design of end tabs for quasi-static and

fatigue testing of fibre-reinforced composites,” Polym. Compos., vol. 30, no. 4, pp. 381–390,

, doi:

G. L. Richards, T. P. Airhart, and J. E. Ashton, “Off-Axis Tensile Coupon Testing,” J. Compos.

Mater., vol. 3, no. 3, pp. 586–589, Mar. 1969, doi: 10.1177/002199836900300322.

D. W. Oplinger, K. R. Gandhi, and B. S. Parker, “Studies of Tension Test Specimens for

Composite Material Testing,” 1982.

M. Lévesque, M. D. Gilchrist, and B. Fisa, “A theoretical study of the tensile test for highly

anisotropic composite materials,” ASTM Spec. Tech. Publ., no. 1436, pp. 320–335, 2003, doi:


M. Hojo, Y. Sawada, and H. Miyairi, “Influence of clamping method on tensile properties of

unidirectional CFRP in 0° and 90° directions - round robin activity for international

standardization in Japan,” Composites, vol. 25, no. 8, pp. 786–796, 1994, doi: 10.1016/0010-


C. T. Sun and I. Chung, “An oblique end-tab design for testing off-axis composite specimens,”

Composites, vol. 24, no. 8, pp. 619–623, 1993, doi:


M. Kawai, M. Morishita, H. Satoh, S. Tomura, and K. Kemmochi, “Effects of end-tab shape on

strain field of unidirectional carbon/epoxy composite specimens subjected to off-axis tension,”

Compos. Part A Appl. Sci. Manuf., vol. 28, no. 3, pp. 267–275, 1997, doi: 10.1016/S1359-


J. C. Marín, J. Justo, A. Barroso, J. Cañas, and F. París, “On the optimal choice of fibre

orientation angle in off-axis tensile test using oblique end-tabs: Theoretical and experimental

studies,” Compos. Sci. Technol., vol. 178, pp. 11–25, 2019, doi:


C. C. Chamis, “Mechanics of Composite Materials: Past, Present, and Future,” J. Compos.

Technol. Res., vol. 11, no. 1, pp. 3–14, Mar. 1989, doi: 10.1520/CTR10143J.

V. L. Kulakov, Y. M. Tarnopol’skii, A. K. Arnautov, and J. Rytter, “Stress-strain state in the

zone of load transfer in a composite specimen under uniaxial tension,” Mech. Compos. Mater.,

vol. 40, no. 2, pp. 91–100, 2004, doi: 10.1023/B:MOCM.0000025483.37317.e2.


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