This critical review provides a processing-structure-property perspective on recent advances in cellulose nanoparticles and composites produced from them. It summarizes cellulose nanoparticles in terms of particle morphology, crystal structure, and properties. Also described are the self-assembly and rheological properties of cellulose nanoparticle suspensions. The methodology of composite processing and resulting properties are fully covered, with an emphasis on neat and high fraction cellulose composites. Additionally, advances in predictive modeling from molecular dynamic simulations of crystalline cellulose to the continuum modeling of composites made with such particles are reviewed (392 references).

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Cellulose nanomaterials review: structure, properties and nanocomposites

This work presents the analytic and experimental development of piezoelectric actuators as elements of intelligent structures, i.e., structures with highly distributed actuators, sensors, and processing networks. Static and dynamic analytic models are derived for segmented piezoelectric actuators that are either bonded to an elastic substructure or embedded in a laminated composite. These models lead to the ability to predict, a priori, the response of the structural member to a command voltage applied to the piezoelectric and give guidance as to the optimal location for actuator placement. A scaling analysis is performed to demonstrate that the effectiveness of piezoelectric actuators is independent of the size of the structure and to evaluate various piezoelectric materials based on their effectiveness in transmitting strain to the substructure. Three test specimens of cantilevered beams were constructed: an aluminum beam with surface-bonded actuators, a glass/epoxy beam with embedded actuators, and a graphite/epoxy beam with embedded actuators. The actuators were used to excite steady-state resonant vibrations in the cantilevered beams. The response of the specimens compared well with those predicted by the analytic models. Static tensile tests performed on glass/epoxy laminates indicated that the embedded actuator reduced the ultimate strength of the laminate by 20%, while not significantly affecting the global elastic modulus of the specimen.

Use of piezoelectric actuators as elements of intelligent structures

This paper provides an overview of recent progress made in the area of cellulose nanofibre-based nanocomposites. An introduction into the methods used to isolate cellulose nanofibres (nanowhiskers, nanofibrils) is given, with details of their structure. Following this, the article is split into sections dealing with processing and characterisation of cellulose nanocomposites and new developments in the area, with particular emphasis on applications. The types of cellulose nanofibres covered are those extracted from plants by acid hydrolysis (nanowhiskers), mechanical treatment and those that occur naturally (tunicate nanowhiskers) or under culturing conditions (bacterial cellulose nanofibrils). Research highlighted in the article are the use of cellulose nanowhiskers for shape memory nanocomposites, analysis of the interfacial properties of cellulose nanowhisker and nanofibril-based composites using Raman spectroscopy, switchable interfaces that mimic sea cucumbers, polymerisation from the surface of cellulose nanowhiskers by atom transfer radical polymerisation and ring opening polymerisation, and methods to analyse the dispersion of nanowhiskers. The applications and new advances covered in this review are the use of cellulose nanofibres to reinforce adhesives, to make optically transparent paper for electronic displays, to create DNA-hybrid materials, to generate hierarchical composites and for use in foams, aerogels and starch nanocomposites and the use of all-cellulose nanocomposites for enhanced coupling between matrix and fibre. A comprehensive coverage of the literature is given and some suggestions on where the field is likely to advance in the future are discussed.

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Review: current international research into cellulose nanofibres and nanocomposites

Hexagonal ferrites: A review of the synthesis, properties and applications of hexaferrite ceramics

The numerical implementation of the model of brittle fracture developed in Francfort and Marigo (1998. J. Mech. Phys. Solids 46 (8), 1319–1342) is presented. Various computational methods based on variational approximations of the original functional are proposed. They are tested on several antiplanar and planar examples that are beyond the reach of the classical computational tools of fracture mechanics.

Numerical experiments in revisited brittle fracture

Linear and Nonlinear Vibration of Composite Plates

The goal of this study is to investigate the feasibility of using a piezoelectric active fin structure as an integrated steering device in small scale airborne devices under realistic aerodynamic loads. The investigation is conducted via a systematic approach for the preliminary design and optimization of the active structural member. This approach provides a graphical representation of the response spectrum of the active structure and enables the coupling of the structural and aerodynamic analyses, which can be conducted independently. The structural analysis adopts analytical and computational tools that are based on the High Order Sandwich Panel Theory, which is extended to include the effects of the active layers and a nonrectangular plane form layouts. The aerodynamic model uses a finitedifference based overset grid approach. Emphasis is laid on the quantitative study of the behavior of an active fin using piezoelectric beam actuators and subjected to various flight conditions. The influence of various mechanical and geometrical properties of the passive and active constituents is investigated. Cases involved with destabilizing aerodynamic effects are also discussed. The results quantitatively reveal the performance envelope of the active fin, provide guidelines for its design, and designate the domain in which the use of such structurally active element is feasible.

Analysis, design, and structural-aerodynamic coupling of a piezoelectric active fin

In the entire text to this point, attention has been focused on the isothermal elastic behavior of classical shells. The effect that temperature distributions within the shell may have on stresses, strains and displacements has not been discussed.

Thermoelastic Effects on Shells

Vibrations of Isotropic Beams and Plates

Through the previous chapter, the static behavior of beams, rods, columns, and plates has been treated to determine displacements and stresses. This is important because many structures are stiffness critical (maximum deflections are limited) or strength critical (maximum stresses are limited). In Chapter 7, the elastic stability of these structures was treated because that is a third way in which structures can be rendered useless. In most cases when a structure becomes elastically unstable, it cannot fulfill its structural purpose.

Jack R. Vinson

Papers

Linear and Nonlinear Vibration of Composite Plates

Analysis, design, and structural-aerodynamic coupling of a piezoelectric active fin

Thermoelastic Effects on Shells

Vibrations of Isotropic Beams and Plates

The Vibrations of Beams and Plates