Calibration of a finite element composite delamination model by experiments

This paper deals with the mechanical behavior under in plane compressive loading of thick and mostly unidirectional glass fiber composite plates made with an initial embedded delamination. The delamination is rectangular in shape, causing the separation of the central part of the plate into two distinct sub-laminates. The work focuses on experimental validation of a finite element model built using the 9-noded MITC9 shell elements, which prevent locking effects and aiming to capture the highly non linear buckling features involved in the problem. The geometry has been numerically defined by a previously established modeling strategy (Branner et al., 2011; Gaiotti & Rizzo, 2011), using a pure shell model where the delamination is accounted for by properly offsetting its surfaces and connecting them to the intact plate via rigid link constraining algorithms. The numerical model developed by the University of Genova is compared with the experimental results provided by an extensive experimental campaign conducted by the Department of Wind Energy at the Technical University of Denmark (Branner & Berring, 2011). Along with the experimental/numerical comparison, an attempt to identify the fracture modes related to the production methods is presented in this paper. A microscopic analysis of the fracture surfaces was carried out in order to better understand the failure mechanisms.