Failure analysis of R-regions of CFRP hat-shaped structure under pull-off load

As a kind of typical structure, the hat-shaped structure (HSS) is widely used in carbon fiber reinforced plastics (CFRP) aircraft parts. In this work, a scheme of filling fillers and adding reinforcing plies in R-regions was proposed to strengthen the R-regions of HSS. Moreover, the force analysis of R-region with or without strengthening in R-region under pull-off load was presented. A finite element model was developed to study the failure behavior of R-regions. A series of HSS samples were fabricated by co-curing process. The pull-off tests of HSS were conducted to validate the model, and the failure mechanism of R-regions was further studied by characterizing the macro-micro structure of R-regions in HSS under pull-off load. Results showed that the structural bearing capacity of HSS can be improved by strengthening in R-regions. After strengthening in R-regions, the pull-off load was borne by multiple interfaces, and the interlaminar interface pull-off strength can increase by 38.8 %.