Chiara Bisagni

Bio: Chiara Bisagni is an academic researcher from Delft University of Technology. The author has contributed to research in topics: Buckling & Finite element method. The author has an hindex of 27, co-authored 153 publications receiving 2184 citations. Previous affiliations of Chiara Bisagni include Polytechnic University of Milan & University of California, San Diego.

Numerical Analysis and Experimental Correlation of Composite Shell Buckling and Post-Buckling

Abstract: This paper deals with the buckling and post-buckling behaviour of carbon fibre reinforced plastic cylindrical shells under axial compression. The finite element analysis is used to investigate this problem and three different types of analysis are compared: eigenvalue analysis, non-linear Riks method and dynamic analysis. The effect of geometric imperfection shape and amplitude on critical loads is discussed. A numerical–experimental correlation is performed, using the results of experimental buckling tests. The geometric imperfections measured on the real specimens are accounted for in the finite element model. The results show the reliability of the method to follow the evolution of the cylinder shape from the buckling to the post-buckling field and good accuracy in reproducing the experimental post-buckling behaviour.

Analytical formulation for local buckling and post-buckling analysis of stiffened laminated panels

Abstract: This paper presents an analytical formulation for the study of linearized local skin buckling load and nonlinear post-buckling behaviour of isotropic and composite stiffened panels subjected to axial compression. The skin is modelled as a thin plate introducing Donnell-Von Karman and Kirchhoff hypothesis and applying classical lamination theory, while the stiffeners are considered as torsion bars. The first part of the work deals with the study of linearized buckling load, and two analytical solutions are presented: one is based on Kantorovich method and the other one on Ritz method. The second part of the work regards the development of a semi-analytical formulation for the study of the post-buckling field, using a variational approach and applying Ritz method. Results are compared with a serie of finite element analysis. It is shown that analytical buckling loads differ from numerical ones for less than 12%, and that force–displacement curves are well predicted. A computer program called stiffened panels analysis (StiPAn) is developed on the basis of the presented formulation. It allows quick analysis of stiffened laminated panels and is suited to be used in optimization routines for preliminary design.

On the crashworthiness performance of thin-walled energy absorbers: Recent advances and future developments

Abstract: Over the past several decades, a noticeable amount of research efforts has been directed to minimising injuries and death to people inside a structure that is subjected to an impact loading. Thin-walled (TW) tubular components have been widely employed in energy absorbing structures to alleviate the detrimental effects of an impact loading during a collision event and thus enhance the crashworthiness performance of a structure. Comprehensive knowledge of the material properties and the structural behaviour of various TW components under various loading conditions is essential for designing an effective energy absorbing system. In this paper, based on a broad survey of the literature, a comprehensive overview of the recent developments in the area of crashworthiness performance of TW tubes is given with a special focus on the topics that emerged in the last ten years such as crashworthiness optimisation design and energy absorbing responses of unconventional TW components including multi-cells tubes, functionally graded thickness tubes and functionally graded foam filled tubes. Due to the huge number of studies that analysed and assessed the energy absorption behaviour of various TW components, this paper presents only a review of the crashworthiness behaviour of the components that can be used in vehicles structures including hollow and foam-filled TW tubes under lateral, axial, oblique and bending loading.

Bioinspired hierarchical composite design using machine learning: simulation, additive manufacturing, and experiment

Abstract: Biomimicry, adapting and implementing nature's designs provides an adequate first-order solution to achieving superior mechanical properties. However, the design space is too vast even using biomimetic designs as prototypes for optimization. Here, we propose a new approach to design hierarchical materials using machine learning, trained with a database of hundreds of thousands of structures from finite element analysis, together with a self-learning algorithm for discovering high-performing materials where inferior designs are phased out for superior candidates. Results show that our approach can create microstructural patterns that lead to tougher and stronger materials, which are validated through additive manufacturing and testing. We further show that machine learning can be used as an alternative method of coarse-graining – analyzing and designing materials without the use of full microstructural data. This novel paradigm of smart additive manufacturing can aid in the discovery and fabrication of new material designs boasting orders of magnitude increase in computational efficacy over conventional methods.

On design optimization for structural crashworthiness and its state of the art

Abstract: Optimization for structural crashworthiness and energy absorption has become an important topic of research attributable to its proven benefits to public safety and social economy. This paper provides a comprehensive review of the important studies on design optimization for structural crashworthiness and energy absorption. First, the design criteria used in crashworthiness and energy absorption are reviewed and the surrogate modeling to evaluate these criteria is discussed. Second, multiobjective optimization, optimization under uncertainties and topology optimization are reviewed from concepts, algorithms to applications in relation to crashworthiness. Third, the crashworthy structures are summarized, from generically novel structural configurations to industrial applications. Finally, some conclusions and recommendations are provided to enable academia and industry to become more aware of the available capabilities and recent developments in design optimization for structural crashworthiness and energy absorption.

Buckling-induced smart applications: recent advances and trends

Abstract: A paradigm shift has emerged over the last decade pointing to an exciting research area dealing with the harnessing of elastic structural instabilities for ‘smart’ purposes in a variety of venues. Among the different types of unstable responses, buckling is a phenomenon that has been known for centuries, and yet it is generally avoided through special design modifications. Increasing interest in the design of smart devices and mechanical systems has identified buckling and postbuckling response as a favorable behavior. The objective of this topical review is to showcase the recent advances in buckling-induced smart applications and to explain why buckling responses have certain advantages and are especially suitable for these particular applications. Interesting prototypes in terms of structural forms and material uses associated with these applications are summarized. Finally, this review identifies potential research avenues and emerging trends for using buckling and other elastic instabilities for future innovations.