Delamination buckling of a laminated composite shell panel using cohesive zone modelling

Laminated composite shell panels take part in several engineering structures. Due to their complex nature, failure modes in composites are highly dependent on the geometry, direction of loading and orientation of the fibers. However, the design of composite parts is still a delicate task because of these fiber failure modes, which includes matrix failure modes or other so-called interlaminar interface failure such as delamination, that corresponds to the separation of adjacent layers of the laminate as a consequence of the weakening of interface layer between them. In this work, impact-induced delamination represented as a circular single delamination is investigated, as it can reduce greatly the structural integrity without getting detected. Furthermore, attention is focused on its effect upon the post-buckling response and the compressive strength of a composite panel. The delamination buckling was modelled using the cohesive element technique under Abaqus software, in order to predict delamination growth and damage propagation while observing their effects on the critical buckling load.

Delamination Buckling of FRP Strips in Strengthened Structural RC Beams and Masonry Walls

This paper deals with delamination buckling of fibre-reinforced polymer (FRP) strips glued to reinforced concrete (RC) beams or to heterogeneous material as masonry. In the field of rehabilitation of existing civil structures, the strengthening using composite materials is becoming a frequent technique although many points have not yet been clarified. The delamination of FRP strips' layer can be often the cause of loss of the strength capacity in strengthened elements. In general, the delamination is due to loss of adhesion of FRP on the adherent material under tensile loading. This type of delamination foresees a slip of FRP strip and development of fracture energy until the detachment. Delamination buckling of FRP strips is instead due to compression loading. Although the FRP is usually adopted to improve the tensile capacity, in civil structural elements subjected to cycle loading, as RC frames in seismic areas or masonry cross walls, the loading is cyclic and the strengthening of FRP strips may be subjected to compressive stresses with separation of the layer from the adherent element. This type of delamination may significantly influence the strength, stiffness and stability. In this paper experiments on the strengthening of RC beams and masonry walls with GlassFRP strips are shown further, analytical and numerical analysis have been developed to study this mechanism of delamination which too often has been missed in the design of strengthening with FRP strips.

Delamination Buckling and Crack Propagation Simulations in Fiber-Metal Laminates Using xFEM and Cohesive Elements

Simulation of fracture in fiber-reinforced plastics (FRP) and hybrid composites is a challenging task. This paper investigates the potential of combining the extended finite element method (xFEM) and cohesive zone method (CZM), available through LS-DYNA commercial finite element software, for effectively modeling delamination buckling and crack propagation in fiber metal laminates (FML). The investigation includes modeling the response of the standard double cantilever beam test specimen, and delamination-buckling of a 3D-FML under axial impact loading. It is shown that the adopted approach could effectively simulate the complex state of crack propagation in such materials, which involves crack propagation within the adhesive layer along the interface, and its diversion from one interface to the other. The corroboration of the numerical predictions and actual experimental observations is also demonstrated. In addition, the limitations of these numerical methodologies are discussed.

Modelling Cracked Cross-Ply Laminates with Delamination Buckling

The mechanical behavior of cross-ply laminates loaded under in-plane compression containing matrix cracks and delaminations is investigated in order to study their influence on the structural stability behavior. This is done by employing a semi-analytical modelling approach which comprises an analytical framework for a structural stability analysis of damageable structures and the Equivalent Constrained Model for deriving reduced stiffness properties of the cracked layers. Cross-ply laminates with varying delamination depths as well as varying matrix crack densities are studied.