Numerical Interlaminar Shear Damage Analysis of Fiber Reinforced Composites Improved by ZnO Nanowires

The applications of carbon fiber reinforced polymer (CFRP) composites have been growing rapidly based on their outstanding properties, such as lightweight, high stiffness, and high strength. Investigation and prediction of the damage initiation and evolution in these structures is a very crucial subject. The interfacial bonding between fiber and matrix or between two plies has a significant rule in the composite performance, considering that the weak interface can cause catastrophic failures in CFRP structures. In this regard, evaluating the interlaminar shear damage of composites and the ways to enhance the interlaminar shear strength (ILSS) is of great importance. Three-point bending (3PB) analysis of short composite beams developed by the American society for testing and materials (ASTM D2344) can be used to study the ILSS and the delamination failure in CFRP laminated. Several approaches have been reported in the literature for improving the ILSS. Hybrid composites in which the nanoparticles are grown on the fibers/lamina is one of the novel methods to enhance the interfacial bonding between the plies. Recently, it is shown that growing Zinc oxide (ZnO) nanowires on the fiber improves the interfacial shear strength of hybrid composites.

 In this study, the multi-scale modeling of hybrid carbon fiber reinforced composite short beam with vertically aligned ZnO nanowires under 3PB loading is investigated. The effect of growing nanowires on improving the ILSS in hybrid structures is explored. The multi-scale analysis acts as a bridge between different length scales in hybrid structures, including micro-scale, meso-scale, and macros-scale. The vertically aligned ZnO nanowires on the lamina and embedded in the epoxy matrix creates an improvement layer. The effective material properties of this layer are evaluated at micro-scale by homogenization analysis. The cohesive zone method is employed in the meso-scale to explore the interfacial behavior and delamination (interlaminar damage) between the homogenized stacking layer and the CFRP lamina. Besides, the strain-based failure criterion is implemented at the macro-scale to investigate the continuum progressive intralaminar damage model (failure in matrix and fiber) of CFRP plies. This analysis is programmed in user-defined mechanical material behavior (VUMAT) linked to ABAQUS finite element software. The three-dimensional (3D) hybrid composite short beam in 3PB load is simulated in ABAQUS Explicit packager. The damage behavior of hybrid composite is compared to the CFRP beam, and improvement in ILSS is observed. The effect of different lengths and diameters of ZnO nanowires and various carbon fiber orientation angles on the ILSS is studied.