Progressive damage analysis on composite laminates stepped-patch adhesively bonding repair

A three-dimensional(3D) FEM was proposed for the progressive damage analysis(PDA) of the stepped-patch bonding repaired composite laminate. Both of the composite laminate and adhesive damage progressing and acting on each other during the process of failure were taken into account. The laminate was modeled with the constitutive equations of continuum damage mechanics(CDM) in an orthotropic damage with a second-order tensor as the internal state variables to describe the damage status of material points. The adhesive layer was modeled with the constitutive equation of CDM in an isotropic damage with a constant internal state variable. The good agreement between the results of the proposed FEM and the experiments shows that the proposed FEM could well predict the tensile strength of laminates repaired with bonded stepped-patch and the whole process of repaired laminates failure.