Giovanni Zucco - Academia.edu (original) (raw)

Papers by Giovanni Zucco

AIAA Scitech 2021 Forum, Jan 4, 2021

Lecture notes in mechanical engineering, 2020

The optimisation of the structural behaviour of the wing is one of the key aspects in the design ... more The optimisation of the structural behaviour of the wing is one of the key aspects in the design of future aircraft. Enhanced freedom to designers has been offered by the stiffness-tailoring capability of Variable Angle Tow (VAT) laminates. Efficient and robust optimisation strategies are, consequently, of great importance to fully explore such an increased design domain. Simultaneously, taking account of the initial postbuckling behaviour can provide hidden load-bearing capability, leading to reduction in weight and costs. In this work we propose an optimisation strategy of the postbuckling behaviour of a recently-proposed VAT wingbox. Being based on an efficient reduced order model for the evaluation of the equilibrium path and on robust stochastic algorithms for the solution of the optimisation problem, the approach shows its viability as a general design tool for buckling dominated structures. Manufacturing constraints are included and the influence of geometrical imperfections is efficiently handled during the optimisation. Different optimisation scenarios are investigated and results show a much improved solution with respect to the initial VAT design.

2018 AIAA/ASCE/AHS/ASC Structures, Structural Dynamics, and Materials Conference, Jan 7, 2018

Journal of the Royal Aeronautical Society, Jan 22, 2020

Automated manufacturing of thermoplastic composites has found increased interest in aerospace app... more Automated manufacturing of thermoplastic composites has found increased interest in aerospace applications over the past three decades because of its great potential in low-cost, high rate, repeatable production of high performance composite structures. Experimental validation is a key element in the development of structures made using this emerging technology. In this work, a 750 × 640 × 240mm variable-stiffness unitised integrated-stiffener out-ofautoclave thermoplastic composite wingbox is tested for a combined shear-bending-torsion induced buckling load. The wingbox is manufactured by in-situ consolidation using a laserassisted automated tape placement technique. It is made and tested as a demonstrator section located at 85% of the wing semi-span of a B-737/A320 sized aircraft. A bespoke in-house test rig and two aluminium dummy wingboxes are also designed and manufactured for testing the wingbox assembly which spans more than 3m. Prior to testing, the wingbox assembly and the test rig were analysed using a high fidelity finite element method to minimise the failure risk due to the applied load case. The experimental test results of the wingbox are also compared

Thin-walled Structures, 2021

Aerospace and industries where both localised compliance and weight savings play a central role i... more Aerospace and industries where both localised compliance and weight savings play a central role in design can benefit from using flexible hinges. These morphing structures use no mechanical hinges for folding. They fold by exploiting the limit point, i.e. the Brazier moment, of a geometrically nonlinear structural response characteristic of thin-walled beams under bending. Therefore, a smaller Brazier moment induces smaller non-classical stresses in the hinge during folding. Two aspects make cross-ply laminates attractive for designing flexible hinges. Firstly, the difference between the Brazier moment of an optimal symmetric generic laminate and that of an optimal symmetric cross-ply is relatively small. Secondly, cross-ply laminates do not exhibit extension-shear or bend-twist couplings which can induce complex deformations which can present challenges during design, especially considering that available analytical solutions of the Brazier moment neglect their effects. Driven by these premises, this work contributes to the preliminary design of flexible hinges by offering an analytical solution of the optimum symmetric cross-ply laminate for minimising the Brazier moment, which is subsequently validated through geometrically nonlinear finite element analysis. Moreover, this work provides insights into the prediction of the folding load considering the effects of local buckling instabilities.

Composite Structures, Sep 1, 2014

ABSTRACT A mixed, quadrilateral, 3D plate element is proposed for static linear and buckling anal... more ABSTRACT A mixed, quadrilateral, 3D plate element is proposed for static linear and buckling analysis of folded laminated composite structures. Numerical results show accuracy, comparing to analytical and numerical references, and convergence rate h2h2 measured using an s-norm. These characteristics are due to the self-equilibrated, isostatic state of stress in the element, and to the element kinematics leading to element compliance and compatibility matrix calculations based solely on the interpolation along the element edges. For folded plates, the drilling rotations do not require penalty functions or non-symmetric formulations, thus avoiding spurious energy modes. Buckling analysis is achieved by a corotational formulation, which is possible thanks to the accuracy of rotation approximations. Benchmarking for laminated composite plates includes convergence of displacements and stress-resultants, global error measures, and comparison with literature results.

Thin-walled Structures, May 1, 2015

A novel methodology for imperfection sensitivity analysis is presented. Koiter's perturbation met... more A novel methodology for imperfection sensitivity analysis is presented. Koiter's perturbation method is used to calculate the imperfection paths emanating from mode interaction bifurcations, which occur on the post-buckling paths of the single modes. The Monte Carlo method is used to test a large number of modes and all possible interactions among them. The computational cost is low because of the efficiency of Koiter's method. The demands of Koiter's method for accurate evaluations of higher order derivatives of the potential energy are met by a mixed, corotational element.

Composite Structures, Sep 1, 2016

Thin-walled Structures, 2017

Post-buckling analysis of variable-angle tow composite plates using Koiter's approach and the fin... more Post-buckling analysis of variable-angle tow composite plates using Koiter's approach and the finite element method. Thin-Walled Structures,

AIAA SCITECH 2022 Forum, 2022

2018 AIAA/ASCE/AHS/ASC Structures, Structural Dynamics, and Materials Conference, 2018

Engineering Structures, 2021

Abstract Cylindrical shells under compressive loading are highly sensitive to boundary conditions... more Abstract Cylindrical shells under compressive loading are highly sensitive to boundary conditions. Considering that these structures are connected by surrounding structural components with finite stiffness, an accurate evaluation of the effects of their boundary stiffness is crucial in their design. As such, this work investigates the effect of elastic boundary conditions on the linear buckling behaviour of cylindrical shells under compressive loading. To achieve this goal, a virtual testing investigation on the effect of translational and rotational constraints to the linear buckling response of a quasi-isotropic cylinder subjected to axial compression is performed. Subsequently, the effect of many kinds of constraints on linear buckling behaviour is discussed and interesting insights regarding a significant coupling effect between the radial and tangential translational constraints are given. Results obtained from virtual testing show that seven recurrent buckling mode shapes occur with seven corresponding similar linear buckling loads. Therefore, based on these similarities, seven groups of classical boundary conditions are introduced to classify all possible linear buckling behaviours exhibited by the cylinder under consideration. Finally, these findings can support the development of theoretical models for cascade, or flange, designs of multiple connecting cylinders.

American Society for Composites 2021, 2021

Cut-outs are inevitable in many structural components such as in aircrafts to accommodate windows... more Cut-outs are inevitable in many structural components such as in aircrafts to accommodate windows or openings for access purposes or fasteners. Engineers usually view cut-outs, especially in primary structures, with disfavour as they result in stress/strain concentration and consequently reduced load carrying capability. Local reinforcements usually increase cost and weight to the overall design which is not favourable in aerospace applications. In case of composite panels, emerging advanced manufacturing methods such as 3D printing of automated fiber placement made it possible to continuously steer fibers/tows around a cut-out to potentially alleviate stress/strain concentration problem. Another advantage of tow steering in this case is maintaining the continuity of fiber/tow paths without any fiber cut which precludes ply-level, 3D stress/strain concentration which could otherwise lead to delaminationinduced damage. In this study, potential capability of tow steering around an ell...

Proceedings of the Royal Society A: Mathematical, Physical and Engineering Sciences, 2020

Symmetry plays an integral role in the post-buckling analysis of elastic structures. We show that... more Symmetry plays an integral role in the post-buckling analysis of elastic structures. We show that the post-buckling response of engineering systems with given symmetry properties can be described using a preselected set of buckling modes. Therefore, the main original contribution of this paper is to prove the existence of these influential buckling modes and reveal some insights about them. From an engineering point of view, this study leads to the possibility of reducing computational effort in the analysis of large-scale systems. Firstly, symmetry groups for nonlinear elastic structural problems are discussed. Then, we invoke Curie’s principle and describe the relationship between these groups and related pre-buckling and linear buckling deformation patterns. Then, for structural systems belonging to a given symmetry group, we re-invoke Curie’s principle for describing the relationship between linear buckling modes and post-buckled deformation of the structure. Subsequently, we fu...

Composites Part B: Engineering, 2020

A novel strain-displacement variational formulation for the flexural behaviour of laminated compo... more A novel strain-displacement variational formulation for the flexural behaviour of laminated composite beams is presented, which accurately predicts three-dimensional stresses, yet is computationally more efficient than 3D finite element models. A global third-order and layer-wise zigzag profile is assumed for the axial deformation field through the laminate thickness to account for the effect of both stress-channelling and stress localisation. By using this axiomatic kinematic field, a variational formulation is developed based on an equivalent single layer theory such that the number of unknowns is independent of the number of composite layers. The axial and couple stresses are evaluated from the displacement field, while the transverse shear and transverse normal stresses are computed by the interlaminarcontinuous equilibrium conditions within the framework of the modified couple stress theory. Axial and transverse force equilibrium conditions are imposed via two Lagrange multipliers, which correspond to the axial and transverse displacements. Using this mixed variational approach, both displacements and strains are treated as unknown quantities, resulting in more functional freedom to minimise the total strain energy. In this work, two strain-displacementbased models are developed to investigate the effect of couple stress on the flexural behaviour of composite beams. The first model neglects the presence of couple stress, whilst the second includes couple stress with an additional unknown curvature. The differential quadrature method is used to solve the resulting governing and boundary equations for simply-supported and clamped laminated beams. For the simply-supported case, numerical results from this variational formulation for both models agree well with those from a Hellinger-Reissner stressdisplacement mixed model found in the literature and the 3D elasticity solution given by Pagano. For the clamped laminate, the additional curvature associated with the couple stress plays an important role in accurately predicting stresses, which is confirmed by a high-fidelity 3D finite element model.

AIAA Journal, 2019

Thermoplastic composites offer the potential for reducing the overall manufacturing costs of airc... more Thermoplastic composites offer the potential for reducing the overall manufacturing costs of aircraft structures by allowing continuous production methods to be applied without the ancillary need f...