Micromechanical prediction of damage due to transverse ply cracking under fatigue loading in composite laminates

Abstract

To predict the matrix microcracking of laminated composites under fatigue loading, a novel energy based model is presented in the framework of micromechanics. For this purpose, strain energy release rate (SERR) of microcracks which had been derived previously for the whole laminate, is developed for a lamina, and then is calculated using a stress transfer-based stiffness reduction method. The advantages of the proposed method include its capability to predict the matrix cracking of general lay-ups based on the local stresses and stiffnesses of each plies separately and not being limited to a special stacking sequence. In order to predict micro-cracking propagation of composites under cyclic loading, the coefficients of the modified Paris law are extracted using the available experimental data of crack density–cycle curves. Then using multi-scale modelling and continuum damage mechanics concept, the proposed algorithm is implemented in ANSYS finite element software, as a new user defined material (Usermat). The static progress of failure on [45/−45]s laminate is simulated and the obtained results are compared with the existing experimental data in a good agreement. Finally, the results of implemented fatigue algorithm for different cross-ply laminates under different stress levels are obtained and compared with the available experimental data.

Effect of fatigue loading on stiffness degradation, energy dissipation, and matrix cracking damage of CFRP [±45]3Scomposite laminate

“…However, the HS specimens with the shortest cycling time exhibited minimum crack density because of delamination and fibre‐dominated final failure. The matrix crack growth parallel to interface (6) leads to sudden delamination but requires very high energy because of interfacial bonding and presence of adjacent layers . This crack mechanism was previously observed for HSF/0.05 as shown in Figure F.…”

“…The matrix crack growth parallel to interface (6) leads to sudden delamination but requires very high energy because of interfacial bonding and presence of adjacent layers. 58 This crack mechanism was previously observed for HSF/0.05 as shown in Figure 6F. The higher stress level provides the desired energy for converting parallel to interface cracks into sudden failure.…”

“…Many proposed elemental life assessment models neither needs additional material properties nor pre‐existing cracks for defining fatigue damage mechanism in MD laminates. However, non‐destructive assessment of residual life using experimental data still possesses a substantial challenge for researchers . The combined use of experimental residual stiffness, energy dissipation, and matrix crack density computation approach as explained in this paper provides a comparative life monitoring approach for any stacking sequence.…”

“…However, non-destructive assessment of residual life using experimental data still possesses a substantial challenge for researchers. [56][57][58][59] The combined use of experimental residual stiffness, energy dissipation, and matrix crack density computation approach as explained in this paper provides a comparative life monitoring approach for any stacking sequence. Here, the computation of normalised stiffness and energy parameter requires load-displacement data whereas the evaluation of matrix crack density needs optical image processing.…”

Investigating the Exergy of Flow and Three Dimensional Flow Study within the Vortex Tube Device Using Computational Fluid Dynamics (CFD)

“…Many laboratory, theoretical and numerical studies have been done to investigate the temperature separation phenomenon in the vortex tube so far. Clearly, using the computational fluid dynamics (CFD) technique, reduces the complexity and cost of empirical works [3][4][5][6][7]. Figure 1 shows the operation of a vortex tube with its components.…”