Imperfection-insensitive continuous tow-sheared cylinders

Lincoln, Reece L; Pirrera, Alberto; Groh, Rainer

doi:10.1016/j.compstruct.2020.113445

Cited by 23 publications

(17 citation statements)

References 43 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…The thickness pattern of these optima have a close resemblance with the imperfection-insensitive hybrid shells proposed by Wagner et al [77], where hoop-oriented belts were installed on top of a monolithic cylindrical shell to achieve the imperfection-insensitive behavior described by the authors. Furthermore, Lincoln et al [78] also reported imperfectioninsensitive designs with hoop-oriented thickness patterns created by CTS, and the encountered optima reported therein also resemble what the inverse ML-driven solver found in the present study. The nonlinear behavior of the optimum configuration with m = 1.448 kg was evaluated using the ABAQUS finite element solver using a mesh of 240 general-purpose elements S4R around the circumference, which have 4 nodes and reduced integration, while keeping the element aspect ratio close to 1.…”

Section: The Inverse Problemsupporting

confidence: 85%

Lightweight Design of Variable-Stiffness Cylinders with Reduced Imperfection Sensitivity Enabled by Continuous Tow Shearing and Machine Learning

Santos

Castro

2022

Materials

View full text Add to dashboard Cite

The present study investigates how to apply continuous tow shearing (CTS) in a manufacturable design parameterization to obtain reduced imperfection sensitivity in lightweight, cylindrical shell designs. The asymptotic nonlinear method developed by Koiter is applied to predict the post-buckled stiffness, whose index is constrained to be positive in the optimal design, together with a minimum design load. The performance of three machine learning methods, namely, Support Vector Machine, Kriging, and Random Forest, are compared as drivers to the optimization towards lightweight designs. The new methodology consists of contributions in the areas of problem modeling, the selection of machine learning strategies, and an optimization formulation that results in optimal designs around the compromise frontier between mass and stiffness. The proposed ML-based framework proved to be able to solve the inverse problem for which a target design load is given as input, returning as output lightweight designs with reduced imperfection sensitivity. The results obtained are compatible with the existing literature where hoop-oriented reinforcements were added to obtain reduced imperfection sensitivity in composite cylinders.

show abstract

Section: The Inverse Problemsupporting

confidence: 85%

Lightweight Design of Variable-Stiffness Cylinders with Reduced Imperfection Sensitivity Enabled by Continuous Tow Shearing and Machine Learning

Santos

Castro

2022

Materials

View full text Add to dashboard Cite

show abstract

“…( 1). The notation used throughout this manuscript is extended from that initially proposed by Gürdal et al [20] and adapted for use in CTS structures by Lincoln et al [15], where a single steered ply with linear variation in fiber angle is denoted by 0…”

Section: A Cts Ply Definitionmentioning

confidence: 99%

“…As Kim noted, the thickness buildup could be exploited to provide enhanced stiffness over a straight tow comparison [7]. This potential for increased structural performance by embedding stiffening features into a laminate was investigated by Lincoln et al, who studied embedded longitudinal stringers and circumferential hoops on a thin-walled cylinder to decrease structural sensitivity to geometric imperfections under axial compression [15]. Subsequently, Lincoln et al utilized a genetic algorithm to optimize cylinders to identify the potential for structural imperfection insensitivity [16].…”

Section: Introductionmentioning

confidence: 99%

“…Tow-steered structures have thus been the subject of numerous FE studies, however little formal investigation into the most accurate element choice for FE modeling of CTS tow-steered structures exists, due to a widespread continuation of choices taken from AFP studies. When FE modeling CTS structures, authors such as Lincoln et al [15,16], Kim et al [17], Groh and Weaver [18], use degenerated shell elements. This manuscript shall refer to these degenerated shell elements as 'conventional shell elements' (S4 or S4R in Abaqus CAE).…”

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

On the Finite Element Discritization of Continuous Tow Sheared Structures

McInnes

Lincoln

Pirrera

et al. 2022

AIAA SCITECH 2022 Forum

View full text Add to dashboard Cite

Tow-steered laminates, those in which the fiber angle varies as a function of in-plane coordinates, represent a substantial numerical modeling problem. In the Continuous Tow Shearing (CTS) process, the tows are deformed by in-plane shearing that generates a non-linear orientation-thickness coupling, which needs to be accounted for when analyzing CTS structures. In this manuscript, an investigation into the Finite Element discretization of CTS structures is conducted to ascertain the most appropriate element choice in terms of computational cost and accuracy. First, natural frequency and buckling eigenvalue analyses are conducted on constant-thickness flat plates and thin-walled cylinders ([±45/0/90] s layup), in order to set a baseline. Next, multiple discretization strategies are implemented to investigate a CTS plate and a thin-walled CTS cylinder by means of two-and three-dimensional shell elements, in linear frequency and buckling analyses. Two CTS stacking sequences are considered, with the first ([±0 0|70 10 ] 2s ) having identical steering across plies, and the second with variable steering across plies ([±0 0|70 10 /±90 0|70 10 ] s ) to increase the discretization difficulty. The use of three-dimensional shell elements allows for greater fidelity in representing the geometry of a CTS structure, as they allow the asymmetric thickness build-ups to be discretized accurately. We show that three-dimensional shell elements enable the use of lower mesh resolutions whilst maintaining solution accuracy, in comparison to two-dimensional shell element meshes of the same geometric in-plane resolution. Moreover, a relation between element type and mesh resolution is presented to appropriately align element centroids and nodal coordinates, for two-and three-dimensional shell elements, respectively, with the maxima of a specific thickness distribution.

show abstract

“…Future research will focus on the direct application of the methodology herein proposed, implemented as provided in the publicly available data set [45]. The investigation will aim at finding imperfection-insensitive shell designs [48,49]. The authors will develop design parameterization schemes enabled by novel manufacturing techniques, such as automated fibre placement [50,51], continuous tow shearing [52], and variable-angle filament winding [27,53,54].…”

Section: Concluding Remarks and Future Researchmentioning

confidence: 99%

Displacement-based multi-modal formulation of Koiter's method applied to cylindrical shells

Castro¹,

Jansen²

2021

Preprint

View full text Add to dashboard Cite

The multi-modal formulation of Koiter's asymptotic method provides a systematic and efficient procedure to evaluate the initial post-buckling behaviour and to assess the nonlinear behavior of structures. This manuscript presents a displacement-based multi-modal formulation of Koiter's method for cylindrical shells, which are structures known for their high imperfection sensitivity and for having clustered bifurcation modes that highly interact. A third-order interpolation is used for the in-plane and out-of-plane displacements by means of the Bogner-Fox-Schmit-Castro (BFSC) element, with 4 nodes and 10 degrees-of-freedom per node, aiming at an accurate representation of the second-order fields required in the initial post-buckling analysis. The single-curvature of the shell is considered in the finite element kinematics and the study includes nonlinear kinematics from Von Kármán and Sanders. The mesh is obtained by closing the circumferentially oriented coordinate at the position where the mesh completes one revolution about the shell perimeter. The proposed formulation and implementation is verified in detail by comparing results for composite shells against established literature for multi-mode asymptotic expansions. A fast convergence of the proposed formulation is observed for linear buckling, pre-buckling state and the initial post-buckling coefficients. The developed formulation enables a close relationship between formulae and the implemented code, and is implemented using state-of-the-art collaborative software. The authors made the implemented routines in a publicly available data set with the aim to popularize Koiter's method.

show abstract

Imperfection-insensitive continuous tow-sheared cylinders

Cited by 23 publications

References 43 publications

Lightweight Design of Variable-Stiffness Cylinders with Reduced Imperfection Sensitivity Enabled by Continuous Tow Shearing and Machine Learning

Lightweight Design of Variable-Stiffness Cylinders with Reduced Imperfection Sensitivity Enabled by Continuous Tow Shearing and Machine Learning

On the Finite Element Discritization of Continuous Tow Sheared Structures

Displacement-based multi-modal formulation of Koiter's method applied to cylindrical shells

Contact Info

Product

Resources

About