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) 5

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a

max

max tran

a

(1)

2 ( ) ( S      − + + 2 ) ( ) ( ) 11 11 22 22 12 2 X X Y

2

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2.3. General design approach and validation The specimen design is carried out using the finite element simulation method. All possible initial geometries are considered and applied to a tension-tension biaxial static load in the software “ Abaqus ” , and then the four criteria are used to evaluate their performance and determine the shape. Next, the dimension of the specimen is continuously modified in the simulation model until the best value is obtained. As for validating the optimized specimen, a manufacturing method that combines additive manufacturing technology with the autoclave process is employed to fabricate the specimen. The manufacturing procedure in Fig. 2 begins with 3D printing of the preliminary mold, followed by the forming of the silicone mold, and ends with the curing of the composites by autoclave. The advantages of the manufacturing method are very few material losses, short time, no post-machining process, and ideal accuracy, due to the features of the additive manufacturing and autoclave process. Thereafter, a fatigue simulation is first conducted on the optimized specimen with a load-controlled mode and a loading frequency of 5 Hz, a stress ratio of 0.1, a constant biaxiality of 1, and a maximum displacement of 0.5 mm on each arm (Fig. 3 (a)). The objective of this simulation is to check if a fatigue failure will first occur in the gauge region. Moreover, another simulation with thermal loading (Fig. 3 (b)) is utilized to demonstrate the specimen’s ability to record temperature variation and characterize thermodynamic responses. This approach enables a full but low-cost validation of the specimen's performance before the formal biaxial fatigue test, which requires a large amount of time and budget on specimen fabrication.

Fig. 2 manufacturing of the cruciform specimen