Micromechanics-based finite element modeling of sandwich structures

Project Information

SANDFECH

Grant agreement ID: 745770

DOI

10.3030/745770

Project closed

EC signature date 27 February 2017

Start date 23 August 2017

End date 22 August 2020

Funded under

• EXCELLENT SCIENCE - Marie Skłodowska-Curie Actions

Total cost

€ 249 793,20

EU contribution

€ 249 793,20

Coordinated by

AALTO KORKEAKOULUSAATIO SR
Finland

Periodic Reporting for period 2 - SANDFECH (Micromechanics-based finite element modeling of sandwich structures)

Reporting period: 2019-08-23 to 2020-08-22

Summary of the context and overall objectives of the project

In this project, novel microstructure-dependent beam and plate models and finite elements are proposed for steel sandwich panels. Such panels have applications especially in ship building. The all-steel panels can offer weight and material savings in cruise ships because of advantageous weight-to-stiffness ratios. The decreased structural weight enables higher payloads and further renders to better fuel-efficiency, not to mention the space-savings due to the compactness of a sandwich panel in comparison to a stiffened plate.

It depends largely on Europe’s ability to stay ahead in research, development and innovation for the current shipbuilding jobs to stay in Europe by developing new solutions like the ones in this project. After all, European shipyards and maritime equipment manufacturers (propulsion, automation, etc.) employ more than half a million people directly and nearly as much indirectly, working at around 300 shipyards and 22,000 supplying companies. Europeans have long been outperformed by their Japanese, South Korean and Chinese rivals in orders for large, standardised ships such as oil tankers and bulk carriers. Nonetheless, the European shipyards still have the strongest footing in advanced shipbuilding including high-value-added products like cruise ships, icebreakers and research vessels, each of which is typically a one-of-a-kind showpiece of engineering. Ultimately, the simple but accurate beam and plate models developed in this project will enable 20–30% more weight-efficient structural designs and will speed-up a simulation-based design process at least 50% mainly by scrapping computationally costly 3-D finite element models. In a cruise ship, weight savings of such magnitude make it possible to add another cabin deck to the ship. The developed structural models can also be used to model beams and plates made of architected lattice materials which are gaining popularity with the rise of additive manufacturing (3-D printing) technologies.

Work performed from the beginning of the project to the end of the period covered by the report and main results achieved so far

An analytical 1-D (micropolar) model for steel sandwich beams considering both static and dynamic behavior was developed. A method to obtain parameters for different structural sandwich cores was devised as well. Linear and non-linear beam versions and the related finite elements models were discussed in three peer-reviewed papers published in reputed international journals. Work has also been carried out also for another 1-D (couple-stress) beam model and one peer-reviewed paper has been written and published on this model. The formulated and studied 1-D beam models form the basis for more physically-involved theoretical models for sandwich panels.

As for 2-D plate models which have applications in ship decks, an analytical 2-D (micropolar) plate model for a web-core sandwich panel was derived in the same spirit as the 1-D beam. A peer-reviewed paper was published in the International Journal of Solids and Structures (October 2019) on the plate model. A non-linear finite element model was developed based on the analytical 2-D model and a peer-reviewed paper was published on it in the International Journal of Nonlinear Mechanics. The finite element model is needed for practical engineering designs.

As the final publication that summarized the theoretical and computational results of the project, a journal paper on a hierarchy of lattice core sandwich beam models was written and published (September 2020).

The results of the project were also discussed at a 3-day summer course at Aalto University in June 2019. The course was organized by MSCA Fellow Anssi Karttunen, his supervising professor Jani Romanoff and the hosting professor J.N. Reddy (Texas A&M University). The aim of the course was to give the participants an extended toolset for dealing with problems where classical continuum mechanics-based tools break down because the material (infinitesimal) and structural length scales are of the same order. This length-scale problem arises, for example, in the design of beam-like micro and nanoelectromechanical (MEMS and NEMS) components, and in the modeling of foams and man-made lightweight lattice materials. Practical engineering applications for lattice materials include the sandwich panels of interest in this project that are used in ship and bridge engineering. Each organizer lectured for one day.

During the project, MSCA Fellow Anssi Karttunen attended multiple international conferences and workshops. However, the conference activities for the final dissemination of the project results planned for Summer 2020 were largely canceled due to the COVID-19 outbreak.

Progress beyond the state of the art and expected potential impact (including the socio-economic impact and the wider societal implications of the project so far)

The developed beam and plate models employ, for the first time, a material modeling method which enables the determination of non-classical material parameters in a rational way. All the published journal papers have a considerable amount of novel technical content which revolves around the material (i.e. constitutive) modeling and the contet goes well beyond the state-of-the-art.

In other words, the resulting rational micromechanics-based beam and plate models have none of the shortcomings of their predecessors. The novel analytical and computational approaches remove effectively one or even two spatial dimensions from the analysis of flexible-joint sandwich panels with unidirectional structural cores, or from the analysis of any similar structure. This makes the design of large structures such as ships, bridge decks and residential buildings more tangible, mathematically tractable and computationally cost-effective for practitioners.

Computationally efficient 2-D plate models will be developed for 3-D web-core sandwich panels.