A multiscale strategy for exploring the mechanical behavior of 3D braided composite thin-walled cylinders

The mechanical behavior of 3D braided composite (3DBC) thin-walled cylinders is investigated using a multiscale modeling approach. A curved-surface equivalent block-stacking based (EBSB) cell, is developed using local homogenization, to facilitate the trans-scale information transfer. It enables to simplify the complex architectures of 3DBCs with the reservation of local braided characteristics. The macroscale models have been constructed by arranging the EBSB cells. Subsequently, axial compression tests have been experimentally and numerically carried out on 3DBC thin-walled cylinders. The prediction errors are less than 4%, revealing a good agreement with the experimental measurements. Besides, the macroscale modeling only takes 0.33 h (20 min), confirming the high computational accuracy and efficiency of the multiscale modeling approach. The experimental and numerical results indicate that matrix cracking is the dominant damage mode for the thin-walled cylinder under axial compression. Moreover, various numerical simulations are performed on four types of grid-stiffened thin-walled cylinders, to analyze the enhancement effect of the stiffening-grid designs. In the axial compression loading case, the square-grid-stiffened (SGS) pattern provides higher enhancement of the load-carrying capacity, while the cylinder with the X-grid-stiffened (XGS) pattern performs better during internal pressure, torsional, as well as the combined loading conditions. The numerical results reveal that the damage is prone to initiate within the skin-stiffener transition region, while the skin cracking results in the final failure of the grid-stiffened cylinders.