Assessment of a constitutive model for crushing failure in aerospace composite materials

Abstract

Fibre reinforced polymers are progressively substituting metallic materials in many aerospace structural applications. Composite materials present a higher specific stiffness and strength than metal alloys. In addition, composites show a high corrosion resistance and damage tolerance. However, the failure mechanisms of composite materials are highly complex due to their anisotropic nature. The simulation of damage in composite materials is one of the pressing engineering issues of today. In fact, there are still multiple failure cases that have not been successfully modeled. One of these failure cases is the crushing of the material, which triggers a combination of failure mechanisms that include delamination, matrix cracking, fibre tensile fracture and fibre kinking, and friction. Bolted joints are currently the main option to join composite to composite in civil aerospace structural applications. Accurately predicting the crushing behaviour of composite materials is of special interest for the simulation of bearing failure in mechanically fastened composite joints, which in turn, would allow for more optimal and less dependent on experimental testing joint designs. In this work, the Gutkin continuum damage model, which was developed with the aim of simulating crushing of uni-directional fibre reinforced composite materials, was implemented. The implemented subroutine was validated against the results published by the author. The different features of the model were evaluated and a parametric study was conducted. The Gutkin subroutine was integrated into the existing Fokker subroutine and tested under cyclic tensile-compressive loads. Finally, a compression test on a small laminate was conducted.