Progressive failure of 3-D-stressed laminates: Multiple nonlinearity treated by the failure mode concept (FMC)

Abstract

This contribution focuses the two aspects: The derivation of failure conditions for a unidirectional (UD) lamina with the prediction of initial failure of the embedded laminae and secondly, the treatment of nonlinear, progressive failure of 3-dimensionally stressed laminates until final failure. The failure conditions are based on the so-called Failure Mode Concept (FMC) which takes the symmetries of the UD-lamina homogenized to a ‘material’ into account. For the solution procedure of the multi-nonlinear analysis the secant modulus of the activated failure modes was employed. Each mode is associated to a stress-strain curve, summing up to five in the case of the transversally-isotropic UD-material. The test cases were taken from the ‘World-wide Failure Exercise’ in the UK involving strength criteria and nonlinear analysis in order to obtain accurate stresses. Furthermore, the reserve factor necessary for the Proof of Design is defined and outlined for the cases ‘linear elastic analysis permitted’ and ‘nonlinear analysis mandatory’. An extensive conclusion with outlooks terminates the contribution. This includes a brief comparison of Puck’s and Cuntze’s theory.