Development of a new finite element for composite delamination analysis

A new solid hexahedron element for composite delamination analysis is introduced. The 8-node solid is derived from a 20-node hexahedron element and has three translational and three rotational degrees of freedom. The particularity of this new element is its aptitude to be transformed into two physically independent 4-node shell elements. This separation into two shells is governed by a delamination criterion. Thus, the decrease in mechanical properties due to delamination, i.e., bending stiffness and buckling resistance, is correctly represented independently of the membrane stiffness which, in some cases, might stay intact. This element will be essentially used to model damages on structures like helicopter blades and sine-wave crash absorber beams. The actual classical modelling of such complex structures is onerous. The new element will allow simplifying models and decreasing the calculation time. Experimental tests are carried out on composite structures such as double cantilever beam specimens. The DCB test is modelled using the new element. A delamination criterion based on the virtual crack closure method and beam theory is used to govern the delamination propagation. The numerical simulation correlate well with the experimental results.