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

Composite materials are used in a wide variety of low temperature applications because of their unique and highly tailorable properties. These low temperature applications of composites include their use in Arctic environments and most of them involve dynamic loads. The U.S. Navy stated that under certain conditions naval vessels may encounter strain rate up to 1200/sec. Because the dynamic properties of composite materials may vary widely with strain rate it is important to use these dynamic properties when the loading conditions require it. All too few materials have been characterized both at high strain rates and at low temperature. Still less effort has been spent in trying to model the high strain rate properties to develop a predictive capability. It has been hoped that earlier modeling for

Low Temperature Effects on E-glass/Urethane Composite Materials at High Strain Rates

In considering cylindrical shells of composite anisotropic materials the equilibrium equations, strain-displacement equations and compatibility equations are the same as those used in Chapter 3 for cylindrical shells of isotropic materials. Only the stress-strain relations (i.e. the constitutive relations) differ. For the most general case the proper constitutive relations are given by (14.63) and (14.61).

Cylindrical Shells of Composite Materials

In Chapter 1, composite materials were discussed as well as some of the means for fabricating structural components composed of these composites. Today, the preponderance of uses for composite materials is in the form of laminated beam, plate and shell structural members. These will be discussed in some detail in Chapters 3, 4 and 5.

Anisotropic Elasticity and Laminate Theory

The vibration of cylindrical shells, as well as shells of more complex shapes, is rather involved, far beyond the scope and intended purpose of this text. It is complicated due to several factors: 

a.

All but some very simple modes involve non-axially symmetric mode shapes.




b.

There are numerous shell theories, each of which differ one from the other.




c.

There are several simplifications, such as the Donnell approximations, but it is not clear when they can be made, and obtain accurate results.




d.

The curvature of the shell forces a coupling of the differential equations involving the displacements u 0, v 0, and w.




e.

Many forcing functions of practical importance are also non-axially symmetric.

The Vibration of Cylindrical Shells

The approach in this chapter is to systematically derive the governing equations for an isotropic classical, thin elastic rectangular plate, and subsequently simplify them for the governing equations of an isotropic elastic thin beam.

Jack R. Vinson

Papers

Low Temperature Effects on E-glass/Urethane Composite Materials at High Strain Rates

Cylindrical Shells of Composite Materials

Anisotropic Elasticity and Laminate Theory

The Vibration of Cylindrical Shells

Derivation of the Governing Equations for Beams and Rectangular Plates