Delamination & Buckling Composite Research Papers (original) (raw)

This paper examines the thermal instability of rectangular delaminated composite plates. A solution procedure is presented based on the third-order shear deformation theory by taking into consideration the von Karman geometrical nonlinearity. The proposed model is capable of analyzing both local buckling of the delaminated base laminate and sublaminate as well as the global buckling of the plate. The thermo-mechanical properties are temperature-dependent. The nonlinear equilibrium equations, derived by the minimum total potential energy principle, are solved by using the Ritz method along with the Newton– Raphson iterative procedure. Numerical results shed a light on the effects of embedded delamination, stacking sequences, and boundary conditions on the equilibrium path, thermal bifurcation points, buckling mode, in-plane displacement, normal/shear strain, and bending moment of the composite plates. It is found that the delamination leads to a substantial reduction in the thermal load-carrying capacity. Furthermore, depending on the boundary conditions and stacking sequence, the response of the perfect composite plates could be either of the bifurcation type or of the unique stable path.

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- Postbuckling, Delamination & Buckling Composite, Thermal instability, Composite Plates

"Future sizes of wind turbine rotor blades will exceed 50 m. For transportation, it is favourable to make them in two parts and connect them in a suitable way at the operational site. With the co-operation of industry and research institutes in three countries, a spar beam-connection principle was selected as a possible solution.
The pre-design, including finite element analysis, for the structural details were carried out at DLR, Stuttgart (Germany). LM Glasfiber A/S (Denmark) realised the concept in a 13.4 m GRP blade with a wound tube as a transverse load and bending moment transferring spar stump. The sectional blade was investigated for static and fatigue integrity at DLR up to 5 million load cycles in a sinusoidal one-step test. Strain gauges were applied at those locations shown by the finite element analysis to be critical.
During the fatigue tests, the blade was observed by means of a thermoelastic stress analysis camera (TSA) by CLRC (United Kingdom) with the aim to observe the stress distributions. These measurements located stress concentrations not otherwise predicted by the finite element analysis. At those locations more strain gauges were applied and found to show relatively high stresses. The strain measurements can be used to calibrate the signals shown by the TSA camera.
Thus, on the basis of the combined use of different design and measurement methods, a promising way is shown to find stress “hot spots” in complex composite components and to inform directly and immediately the manufacturers of those articles about possible or necessary modifications."

This paper presents a high accuracy Finite Element approach for delamination modelling in laminated composite structures. This approach uses multi-layered shell element and cohesive zone modelling to handle the mechanical properties and damages characteristics of a laminated composite plate under low velocity impact. Both intralaminar and interlaminar failure modes, which are usually observed in laminated composite materials under impact loading, were addressed. The detail of modelling, energy absorption mechanisms, and comparison of simulation results with experimental test data were discussed in detail. The presented approach was applied for various models and simulation time was found remarkably inexpensive. In addition, the results were found to be in good agreement with the corresponding results of experimental data. Considering simulation time and results accuracy, this approach addresses an efficient technique for delamination modelling, and it could be followed by other researchers for damage analysis of laminated composite material structures subjected to dynamic impact loading