The review outlines modern trends in theoretical developments, novel designs and modern applications of sandwich structures. The most recent work published at the time of writing of this review is considered, older sources are listed only on as-needed basis. The review begins with the discussion on the analytical models and methods of analysis of sandwich structures as well as representative problems utilizing or comparing these models. Novel designs of sandwich structures is further elucidated concentrating on miscellaneous cores, introduction of nanotubes and smart materials in the elements of a sandwich structure as well as using functionally graded designs. Examples of problems experienced by developers and designers of sandwich structures, including typical damage, response under miscellaneous loads, environmental effects and fire are considered. Sample applications of sandwich structures included in the review concentrate on aerospace, civil and marine engineering, electronics and biomedical areas. Finally, the authors suggest a list of areas where they envision a pressing need in further research.

Review of current trends in research and applications of sandwich structures

From flat sheets to curved geometries: Origami and kirigami approaches

Origami, the ancient Japanese art of paper folding, is not only an inspiring technique to create sophisticated shapes, but also a surprisingly powerful method to induce nonlinear mechanical properties. Over the last decade, advances in crease design, mechanics modeling, and scalable fabrication have fostered the rapid emergence of architected origami materials. These materials typically consist of folded origami sheets or modules with intricate 3D geometries, and feature many unique and desirable material properties like auxetics, tunable nonlinear stiffness, multistability, and impact absorption. Rich designs in origami offer great freedom to design the performance of such origami materials, and folding offers a unique opportunity to efficiently fabricate these materials at vastly different sizes. Here, recent studies on the different aspects of origami materials-geometric design, mechanics analysis, achieved properties, and fabrication techniques-are highlighted and the challenges ahead discussed. The synergies between these different aspects will continue to mature and flourish this promising field.

https://par.nsf.gov/servlets/purl/10197964

Architected Origami Materials: How Folding Creates Sophisticated Mechanical Properties.

A Review of Thickness-Accommodation Techniques in Origami-Inspired Engineering

Starting from simple notions of paper folding, a review of current challenges regarding folds and structures is presented. A special focus is dedicated to folded tessellations which are raising interest from the scientific community. Finally, the different mechanical modeling of folded structures are investigated. This reveals efficient applications of folding concepts in the design of structures.

/pdf/from-folds-to-structures-a-review-48wifjfvvg.pdf

From Folds to Structures, a Review:

Sandwich structures with folded cores are regarded as a promising alternative to conventional honeycomb sandwich structures in the aerospace industry. This paper presents a parametric study on the mechanical properties of a variety of Miura-based folded core models virtually tested in quasi-static compression, shear and bending using the finite element method. It is found that the folded core models with curved fold lines exhibit the best mechanical performances in compression and shear while the multiple layered models outperform the other folded core models in bending. Furthermore, the folded core models are compared to a honeycomb core model with the same density and height. In this case, it is shown that the honeycomb core has the best performance in compression while the folded cores have comparable or even better performances in the shear and bending cases. The virtual test results reported in this paper can provide researchers with a general guideline to design the most suitable folded core structure for certain applications.

/pdf/mechanical-properties-of-miura-based-folded-cores-under-4quxgg8qsx.pdf

Mechanical properties of Miura-based folded cores under quasi-static loads

This paper presents a mathematical framework for the design of rigid-foldable doubly curved origami tessellations based on trapezoidal crease patterns that can simultaneously fit two target surfaces with rotational symmetry about a common axis. The geometric parameters of the crease pattern and the folding angles of the target folded state are determined through a set of combined geometric and constraint equations. An algorithm to simulate the folding motion of the designed crease pattern is provided. Furthermore, the conditions and procedures to design folded ring structures that are both developable and flat-foldable and stacked folded structures consisting of two layers that can fold independently or compatibly are discussed. The proposed framework has potential applications in designing engineering doubly curved structures such as deployable domes and folded cores for doubly curved sandwich structures on the aircraft.

https://royalsocietypublishing.org/doi/pdf/10.1098/rspa.2017.0016

Design of rigid-foldable doubly curved origami tessellations based on trapezoidal crease patterns.

A combination of methods of strategy which combines optical measurements and numerical calculations was developed to study the buckling behavior and failure modes of composite panel with M-type stiffeners under compression. Utilizing the non-contact optical means for non-destructive testing, the full-field buckling deflections/evolution and compressive failure of the panel surface were systematically collected for mechanical analysis. Based on continuum mechanics modeling, the buckling and post-buckling behaviors of the composite panel were predicted and compared with the buckling shapes that are obtained from experiments. The numerical simulation methods and experimental test technique in the work provides a useful tool to study the compressive buckling behaviors of composite panel with M-type stiffeners.

Hai Wang

Papers

Mechanical properties of Miura-based folded cores under quasi-static loads

Design of rigid-foldable doubly curved origami tessellations based on trapezoidal crease patterns.

Buckling measurement and numerical analysis of M-type ribs stiffened composite panel