Dynamic behaviour of fibre composite multilayer sandwich plates with delaminations

Composites are continuing to gain prominence for structural as well as non-structural applications all over the world. A structural composite multilayer slab can be manufactured by gluing several of the composite sandwiches together to form a laminated composite slab. Delamination between layers is one of the major failure modes which threaten the reliability of composite structures. Delamination can also cause changes to dynamic behaviour. Dynamic analysis of three dimensional models of structures enables more realistic assessment of their free vibration behaviour. The dynamic behaviour of fibre composite multilayer sandwich plates with different configurations of delamination is presented in this paper. A parametric investigation is carried out to assess the influence of parameters including length, width and location of delamination, size and support conditions of the plates on the free vibration behaviour, using three dimensional modelling with Strand7 finite element software package. Plate elements for skins and brick elements for core of each sandwich layer are used in the model development for plates representing their actual behaviour. It is revealed that the decrease in natural frequency with the increase in the extent of debonding is greatly dependent on the boundary conditions, location of the debond and also on the mode number