Free vibration analysis of variable stiffness composite laminated beams and plates by novel hierarchical differential quadrature finite elements

The usage of printed composites in the aerospace industry has been steadily increasing over the last years. Especially, 3D printers and automatic fibre placement machines have allowed the introduction of Variable Angle Tow (VAT) composites, which theoretically offer greater tailoring capabilities than classic composite laminates. Nevertheless, the steering of brittle fibres is not flaw-exempt and, in fact, is greatly affected by the printer signature. This manuscript aims to examine the influence of fibre misalignments on the stress and failure index distribution in laminated VAT composites. For doing so, the Carrera Unified Formulation (CUF) is employed to develop layerwise models with unprecedented accuracy. Flaws are introduced at the layer scale by means of stochastic fields and uncertainty analysis is carried out through a Monte Carlo analysis. The random variation (defects) is propagated through the scales and correlated with the stress and failure index distribution. The results show that misalignments greatly affect the in-plane normal stresses, which lately influence fibre tension and compression failure mechanisms.

Stochastic stress analysis and failure onset of variable angle tow laminates affected by spatial fibre variations

Uncertainty quantification in buckling strength of variable stiffness laminated composite plate under thermal loading

New concepts of lightweight components are conceived nowadays thanks to the advances in the manufacture of composite structures. For instance, mature technologies such as Automatic Fibre Placement (AFP) are employed in the fabrication of structural parts where fibres are steered along curvilinear paths, namely variable angle tow (VAT), which can enhance the mechanical performance and alleviate the structural weight. This is of utmost importance in the aerospace field, where weight savings are one of the main goals. For that reason, shell structures are commonly found in the aerospace industry because of their capabilities of supporting external loadings. Straight-fibre composite shell structures have been studied in recent decades and, now, spatially varying composite shells are attracting the attention of manufacturers. This work analyses the mechanical behaviour of VAT composite shells subjected to different external loadings and boundary conditions. The Carrera Unified Formulation (CUF) is employed to obtain the different structural models in a systematic and hierarchic manner. The outcomes of such numerical models are discussed and compared with commercial software Abaqus.

Accurate Stress Analysis of Variable Angle Tow Shells by High-Order Equivalent-Single-Layer and Layer-Wise Finite Element Models

Abstract This work intends to present a novel numerical approach for studying the vibration behaviours of variable angle tow (VAT) composite structures in their quasi-static nonlinear equilibrium states. This methodology is able to predict the buckling load, to investigate the natural frequencies variation for progressively higher loads, and to provide a means for verifying experimental Vibration Correlation Technique results. The use of VAT composites, in which the fibre orientations are allowed to vary along with a curvilinear pattern within each lamina, dramatically increases the design space and provides a significant improvement in buckling performance and benefits in the postbuckling regime. This study has been performed using an innovative methodology based on the well-established Carrera Unified Formulation able to describe several kinematic models for two-dimensional structures. In detail, layerwise theories are employed to characterize the complex phenomena that may appear in VAT composite structures. All Green-Lagrange strain components are employed because far nonlinear regimes are investigated. Furthermore, the geometrical nonlinear equations are written in a total Lagrangian framework and solved with an opportune Newton–Raphson method along with a path-following approach based on the arc-length constraint. Different VAT composite structures have been analyzed to validate the proposed approach and provide some benchmark solutions. The computed equilibrium paths are compared with results obtained using the commercial code ABAQUS. The results document the good accuracy and reliability of the presented methodology and show this numerical tool’s potentialities. 

https://link.springer.com/content/pdf/10.1007/s00707-022-03226-2.pdf

Geometrically nonlinear analysis and vibration of in-plane-loaded variable angle tow composite plates and shells

Additive manufacturing brought to the emergence of a new class of fiber-reinforced materials; namely, the Variable Angle Tow (VAT) composites. Automated fiber placement machines allow the fibers to...

Influence of fiber misalignments on buckling performance of variable stiffness composites using layerwise models and random fields

It is well known that fabrication processes inevitably lead to defects in the manufactured components. However, thanks to the new capabilities of the manufacturing procedures that have emerged during the last decades, the number of imperfections has diminished while numerical models can describe the ground truth designs. Even so, a variety of defects has not been studied yet, let alone the coupling among them. This paper aims to characterise the buckling response of Variable Stiffness Composite (VSC) plates subjected to spatially varying fibre volume content as well as fibre misalignments, yielding a multiscale sensitivity analysis. On the one hand, VSCs have been modelled by means of the Carrera Unified Formulation (CUF) and a layer-wise (LW) approach, with which independent stochastic fields can be assigned to each composite layer. On the other hand, microscale analysis has been performed by employing CUF-based Mechanics of Structure Genome (MSG), which was used to build surrogate models that relate the fibre volume fraction and the material elastic properties. Then, stochastic buckling analyses were carried out following a multiscale Monte Carlo analysis to characterise the buckling load distributions statistically. Eventually, it was demonstrated that this multiscale sensitivity approach can be accelerated by an adequate usage of sampling techniques and surrogate models such as Polynomial Chaos Expansion (PCE). Finally, it has been shown that sensitivity is greatly affected by nominal fibre orientation and the multiscale uncertainty features.

https://www.mdpi.com/1996-1944/14/11/2706/pdf

Alberto Racionero Sanchez-Majano

Papers

Influence of fiber misalignments on buckling performance of variable stiffness composites using layerwise models and random fields

Stochastic stress analysis and failure onset of variable angle tow laminates affected by spatial fibre variations

Accurate Stress Analysis of Variable Angle Tow Shells by High-Order Equivalent-Single-Layer and Layer-Wise Finite Element Models

Buckling Sensitivity of Tow-Steered Plates Subjected to Multiscale Defects by High-Order Finite Elements and Polynomial Chaos Expansion.

Microscale thermo-elastic analysis of composite materials by high-order geometrically accurate finite elements