▎ 摘　　要

Effective elastic properties of the graphene nanoplatelet (GNP)/unidirectional glass fiber (GF)-reinforced polyimide composites subjected to off-axis loading are predicted using a closed-form hierarchical micromechanical approach. The effects of volume fraction, agglomeration and non-flat structure of GNPs, graphene/polymer interfacial region, and fiber volume fraction on the off-axis elastic modulus and off-axis Poisson's ratio are investigated. In order to verify the accuracy of the present micromechanical method, predictions are compared with the experimental data. Adding GNPs into the polymeric resin increases the elastic modulus of all off-axis coupons. When flat GNPs are uniformly dispersed in the polyimide resin, much more improvement in the off-axis elastic properties is achieved. The results indicate that agglomeration and non-flat structure of the GNP can drastically decrease the off-axis elastic modulus. It is observed that the off-axis elastic response of hybrid composites may be sensitive to the material property and thickness of the interfacial region.