A global/local third-order Hermitian displacement field with damaged interfaces and transverse extensibility: FEM formulation

For some applications where the transverse normal quantities (displacement, strain and stress) have to be well described, the previously formulated third-order Hermitian zig-zag theory needs some improvements; the way we have followed is that of the sublaminates approach. At first a beam finite element based on the Hermitian model has been formulated. Then a discretizing and assembling procedure has been used that enables to divide the laminate thickness in a number of elements-sublaminates. A numerical assessment of the method potentialities is presented: (i) the through-the-thickness description of the transverse normal quantities is improved, (ii) tangentially loaded multilayered beams are also well described and (iii) the interlayer slip problem is studied more accurately. Referring in particular to the latter problem, it is found that the classical and Hermitian (only one sublaminate) cubic zig-zag models cannot be used for very severe levels of damage because the slip-locking phenomenon rises; the use of more than one sublaminates eliminates the problem.