Carbon nanotubes (CNT)-reinforced polymer composite has many engineering applications due to attractive properties, like high strength to weight ratio. These materials are subjected to cyclic fatigue loading during their service life. This work proposed a dual scale modeling approach to predict fatigue crack growth behavior of CNT-reinforced polymer composite under the thermo-mechanical loading environment. The effective orthotropic property of CNT-reinforced polymer composite is estimated using the mean-field homogenization technique in meso-scale modeling. Further, the equivalent composite property is used for macro-scale fatigue crack growth study using higher-order extended finite element method. To present the efficiency of the proposed modeling approach, various combinations of polymer composite (by volume fraction of reinforcement at 7.5%, 10%, 12.5%, 15%, 17.5%, and 20%) are taken for analysis. At macro-scale modeling, XFEM with higher-order enrichment terms is employed to improve the solution accuracy at the crack tip region. The proposed computational approach has been employed with the in-house developed MATLAB code and DIGIMAT software. Several numerical examples are considered with geometrical discontinuities like multiple holes and cracks.

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A novel computational approach presented in this work to improve the accuracy and efficiency of fracture modeling in an orthotropic material medium. Extended finite element method (XFEM) with higher-order enrichment functions was employed at the different scale mesh topology. The approach combined variable node element concepts for different scale mesh connections and higher-order XFEM for accuracy and completeness of discontinuity domain. The proposed computational methodology was employed with in-house developed MATLAB code. Further, stochastic fracture studies were discussed for reliability of the cracked structures. Few numerical examples with multiple geometrical discontinuities were simulated to check the computational efficiency and accuracy.

Patch repairing technique is effective and efficient approach to enhance structural performance of aged aircraft panels. The presented work emphases on studying the patch shape and size effect on scarf composite patch repair of aluminium aircraft panel under thermal, thermo-elastic and mechanical load. In this work, patched repaired structural member has been simulated by ABAQUS software to find out the performance of patch repair in term of patch thickness and patch shape. Five different patch shapes are chosen to analysis: circular, square, hexagonal, rectangular and trapezoidal with different patch thickness 1, 2, 3, 4, 5 mm. The Heat transfer and coupled temp-displacement analysis has been performed under cure temperature 394 K for in-situ patch repair model. The analysis of the critical von-Mises stress and heat flux load distribution in composite patch repair system allows us to estimate performance in composite patch repair system. The results show that patch shape and size has significant effect on magnitude of heat flux load and induced von-Mises stress. Trapezoidal shape of composite patch repair has lower value of von-Mises stress and heat flux load as compared to all four shapes of composite patches.