PSI - Issue 52

Jun Koyanagi et al. / Procedia Structural Integrity 52 (2024) 187–194 Author name / Structural Integrity Procedia 00 (2019) 000 – 000

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4. Studies for Meso-Scale simulations 4.1 Finite element model for simulating entropy-based strength-degradation of carbon-fiber-reinforced plastics subjected to cyclic loadings (Koyanagi et al. 2022) W e develop a finite element for degradable Hashin’s law based on dissipated energy which is almost corresponding to entropy. The strength of fiber axial tensile and compressive and fiber transverse, and shear can decrease in reflect to the loaded history. A linear viscoelastic model shown in Fig. 7 is assumed at the first and then the dissipated energy in six direction is counted respectively and then they are combined thus the entropy is defined. As increase of entropy, the strength and fracture energy decrease as shown in Fig. 8. Using this element, various numerical simulations regarding durability can be implemented in mesoscale viewpoint.

s 1

s 2 s 3 s 4 s 5

e e, 1-5 e v, 1-5

Equivalent stress

Relative displacement

Degradation before damage onset Degradation after damage onset

Fig. 7 Orthotropic viscoelastic constitutive model

Fig. 8 Degradable stress-displacement relationship

4.2 Numerical and Experimental Studies for Fatigue Damage Accumulation of CFRP Cross-Ply Laminates Based on Entropy Failure Criterion (Deng et al. 2023) Using above developed element, we perform numerical simulations for fatigue damage accumulation such as increase of transverse cracking of cross-ply CFRP laminates under various cyclic loading conditions. The numerical model is shown in Fig. 9. The boundary conditions are also depicted here. In this simulation, we adopt strength distributions for all elements which is based on Weibull statistics. In other words, every element has its own strength so that it is unknown where transverse cracking occurs. The numerical results are shown in Fig. 10. In this figure, the failure initiation index is shown in lefthand side and the specific stress components which directly effects on transverse cracking is shown in righthand side. As increase of loading number, the transverse cracking occurs and increase. This numerical simulation is state-of-the-art for fatigue simulation in the composite fields. In this paper presented by Deng et al. 2023, the frequency dependence of increase in transverse cracking is also investigated and the numerical results show good agreement with the experimental results even though it is qualitatively. Thus, we employ entropy-based damage criterion, and various cutting-edge studies are now implemented.