Abstract
This paper presents a new four-node composite element, which incorporates nd delaminations
through its thickness. Based on the extended finite element method (X-FEM) technology,
the element is particularized on a CLT (classical laminate theory). Delamination is
considered in the kinematic equations with additional degrees of freedom. The result is a
four-node quadrilateral element requiring only two single FEM (finite element method) formulations,
a bending one and a membrane one. An important result is that this formulation
has the same accuracy as when separate elements are considered (four region
approach). It is furthermore proven that the delaminated element passes the patch test
if the selected FEM formulations to build the element pass the test in the pure single problems,
making this methodology very attractive to develop other fractured elements. To illustrate
this result, two benchmark problems were studied: first a complete delaminated
cantilever plate, and second a complete delaminated circular plate. The element was tested
in the context of SHM (structural health monitoring). Frequency shifts, damage indexes,
and changes in mode shapes and frequency response functions (FRF) were obtained to
quantify the severity of damage due to delamination.
