PSI - Issue 75

Aijia Li et al. / Procedia Structural Integrity 75 (2025) 318–333 Aijia Li, Christian Garnier, Marie-Laetitia Pastor, Xiaojing Gong, Clément Keller/ Structural Integrity Procedia (2025) 3

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Fig. 1. (a) typical multiaxial fatigue loadings and the corresponding specimen geometry (Quaresimin (2015)); (b) commonly used cruciform specimen with different shapes of the gauge region (Skinner et al. (2020), Skinner et al. (2019) and Moncy et al. (2023))

In this case, this paper aims to optimize the specimen geometry for MD (MultiDirectional) carbon fiber reinforced composites in a tension-tension biaxial fatigue test with temperature measurement. The experimental material and methods are first introduced, and the design criteria are selected: (1) failure in the gauge region; (2) uniform stress in the gauge region; (3) thermography adaptability; (4) easy manufacturing. Subsequently, two stages of numerical simulations using FEM (Finite Element Method) are conducted to determine the shape and dimensions, respectively. Finally, a series of validation simulations considering thermodynamic responses and fatigue loading is employed to evaluate the proposed specimen design, and some tips are provided for similar specimen designs.

Nomenclature α

Failure factor of the Tsai-Hill criterion B Tsai-Hill failure parameter Maximum failure factor α in the gauge region Maximum failure factor α on the transition X

Allowable tensile or compression strength of the ply in the fiber direction Allowable tensile or compression strength of the ply in the transverse direction S Allowable in-plane shear strength of the ply between the fiber and the transverse directions σ 11 Normal stress in the fiber direction σ 22 Normal stress in the transverse direction σ 12 Shear stress between the fiber and the transverse directions R Radius of the specimen’s transition d Diameter of the reduced area of the specimen Y