High-Fidelity 1D and 2D Models for Static and Dynamic Analyses of Wind Turbine Rotor Blades

Wind energy is an essential renewable source to tackle the most critical environmental problems, such as global warming. Recently, the wind blade size has been increasing to maximize turbine efficiency. However, increased dimensions lead to further design challenges due to severe loadings - inertial and aerodynamic - and unavoidable manufacturing complexities. Therefore, extensive simulation campaigns covering as many operational conditions as possible become crucial for sustainable design and manufacturing. Various numerical tools for this purpose have been proposed to predict the response and damage levels of sizeable composite wind turbine blades. Within this context, this paper presents results based on the Carrera Unified Formulation (CUF) on various blade configurations. The CUF is a hierarchical formulation providing classical and higher-order beam, plate, and shell models using arbitrary kinematic expansions. The one-dimensional (1D) and two-dimensional (2D) CUF-based models can ensure a similar accuracy of three-dimensional (3D) solutions with considerable savings in computational efforts. The principle of virtual work and a finite element approximation is used to formulate both geometrically linear and nonlinear governing equations. The numerical results focus on static, dynamic, and failure analyses performed on composite wind turbine blades. The failure index evaluation uses a global/local approach that combines the CUF models with conventional FE solutions. In addition, future challenges related to health monitoring, damage detection, and developing a digital twin for structural verification will be discussed

Thermoelastic micromechanical analysis of CFRP with voids

The work investigates the effect of dispersed air gaps – voids – within the matrix on the local stress and strain fields and the influence on the thermoelastic properties of carbon fiber reinforced plastic polymers (CFRPs). The micromechanics framework is based on the use of 1D higher-order structural theories obtained via the Carrera Unified Formulation (CUF) and periodic boundary conditions (PBC), including plasticity over the matrix. Voids are randomly generated within the matrix, considering different volume fractions. Moreover, several distributions at the same void volume fraction permit to perform statistical analyses of the results. Based on numerical results, increasing void fractions leads to higher stress and strain values. Regarding the thermoelastic properties, the results show a good agreement with the benchmarks, thus confirming that voids have a remarkable effect on thermoelastic properties

Evaluation of transverse shear stresses in layered beams/plates/shells via stress recovery accounting for various CUF-based theories

This paper exploits the stress recovery technique to evaluate the out-of-plane stress components in the static analysis of composite beams, plates and shells. This technique is implemented in the framework of the Carrera Unified Formulation, an approach allowing the implementation of the theories of structures in a compact way. This work uses Taylor, Legendre and Jacobi polynomials with equivalent single-layer and layer-wise approaches. The finite element method is applied to provide numerical solutions. Multi-layered beams, plates and shells subjected to different loading and boundary conditions are studied to validate and assess the proposed technique. The results are compared with those from the literature and show that the stress recovery technique provides reasonable accuracy for the shear stresses, even with lower-order models. Furthermore, results confirm that, when dealing with thick structures, the adoption of layer-wise models is mandatory to obtain accurate results

Compressive damage modeling of fiber-reinforced composite laminates using 2D higher-order layer-wise models

A refined progressive damage analysis of fiber-reinforced laminated composites subjected to compressive loads is presented here. The numerical analysis exploits higher-order theories developed using the Carrera Unified Formulation, specifically 2D plate theories with Lagrange polynomials to enhance the kinematic approximation through each ply’s thickness resulting in a layer-wise structural model. The CODAM2 material model, based on continuum damage mechanics, governs the intralaminar composite damage. The Hashin criteria and the crack-band approach provide failure initiation and propagation, respectively. Fiber micro-buckling and kinking are taken into account via the use of nonlinear post-peak softening models. It is shown that linear-brittle stress-strain softening is effective for accurate compressive strength predictions. A series of numerical assessments on coupon level composite laminates is carried out to verify the proposed numerical framework while its validation is demonstrated by successfully applying the numerical tool to test cases for which experimental data is available from the literature. Various through-the-thickness structural models are evaluated to provide insights for proper modeling. Numerical assessments considered quasi-isotropic laminates, the compressive strength, and size-effects under brittle fracture of notched laminates, and progressive damage characteristics due to stable crack growth in compact compression tests. The results show the possibility of using coarser meshes than those used in standard FEM approaches as the accuracy of predictions is preserved through the use of higher-order structural theories

Static analysis of thin-walled beams accounting for nonlinearities

This paper presents numerical results concerning the nonlinear analysis of thin-walled isotropic structures via 1D structural theories built with the Carrera Unified Formulation (CUF). Both geometrical and material nonlinearities are accounted for, and square, C- and T-shaped beams are considered. The results focus on equilibrium curves, displacement, and stress distributions. Comparisons with literature and 3D finite elements (FE) are provided to assess the formulation’s accuracy and computational efficiency. It is shown how 1D models based on Lagrange expansions of the displacement field are comparable to 3D FE regarding the accuracy but require considerably fewer degrees of freedom

HIGH-FIDELITY DAMAGE ANALYSIS OF COMPOSITES USING A PLY-BASED CONTINUUM MODEL

The current work is based on the implementation of the CODAM2 intralaminar damage model in CUF-Explicit, an explicit nonlinear dynamics solver based on the Carrera Unified Formulation (CUF). The CODAM2 model is based on the concept of continuum damage mechanics, and stress-based failure criteria are used to determine the onset of damage. The damage progression makes use of the crack-band theory to scale the fracture energies, thus ensuring mesh objectivity. The structural modelling is performed using high-order 2D theories based on CUF. 2D elements are used to model the structural geometry, and 1D expansions based on Lagrange polynomials are used to define the thickness, resulting in a layer-wise modelling approach. Numerical assessments are performed considering single elements and tensile coupons. The results are in good agreement with reference numerical solutions and experimental data, thus verifying the current implementation

The ATLAS barrel level-1 Muon Trigger Sector-Logic/RX off-detector trigger and acquisition board

The ATLAS experiment uses a system of three concentric layers of Resistive Plate Chambers (RPC) detector for the Level-1 Muon Trigger in the air-core barrel toroid region. The trigger algorithm looks for hit coincidences within different detector layers inside the programmable geometrical road which defines the transverse momentum cut. The on-detector electronics that provides the trigger and detector readout functionalities collects input signals coming from the RPC front-end. Trigger and readout data are then sent via optical fibres to the off-detector electronics. Six or seven optical fibres from one of the 64 trigger sectors go to one Sector-Logic/RX module, that later elaborates the collected trigger and readout data, and sends data respectively to the Read-Out Driver modules and to the Central Level-1 Trigger. We present the functionality and the implementation of the VME Sector-Logic/RX module, and the configuration of the system for the first cosmic ray data collected using this module