▎ 摘　　要

Flexible, highly sensitive stain sensors prepared from polymer nanocomposites have attracted a great deal of interests, due to the rapid development of robotics, transportation, aerospace and health monitoring. However, these sensors are often limited by unideal mechanical properties, sensitivity and cycling performance. We herein report a facile approach to developing high-cycling performance strain sensors based on a nanocomposite film. The film was prepared by dispersing 3 nm-thick graphene platelets (GnPs) within an epoxy matrix. TEM micrographs confirmed that GnPs were uniformly dispersed in epoxy whilst some were connected to each other, which contributed to the mechanical properties and electrical conductivity of the resulting nanocomposites. At 2.0 vol% GnPs, Young's modulus, fracture toughness and energy release rate of neat epoxy were improved by 93%, 135% and 215%, respectively. Having gauge factors of 1-33, the film sensor demonstrated high sensitivity to tensile strains 0-0.67%. Meanwhile, the film sensor revealed excellent performance over 35,000 cycles due to high fracture toughness and effective dissipation of the heat accumulated during fatigue cycles. Practically, the film sensor also demonstrated effective response to temperature, humidity and damage evolution. This work provides an effective strategy for developing graphene-based strain sensors of excellent mechanical properties, sensitivity and reliability.