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

Shells in which the middle surface is generated by rotating a generator about an axis are called shells of revolution. A closed cylindrical shell is the simplest case, and the analysis of stresses and deformations in such cylindrical shells was treated in Chapter 3. Due to Reissner, Meissner, and Naghdi, a generalized method of analysis can be employed for all shells of revolution subjected to axially symmetric loads without dealing with each shell geometry specifically. This treatment is presented below, because of its extreme usefulness.

Shells of Revolution Subjected to Axially Symmetric Loads

An analytical and experimental investigation is performed to clarify the transverse shear deformations that occur in laminated and sandwich composite plates subjected to in-plane shear loads. This is part of a larger study investigating the feasibility of an in-plane shear test as a practical procedure to determine the in-plane shear modulus and/or strength of various material systems as well as the faces and cores of sandwich plates. The theorem of minimum potential energy has been used to determine the deflections and strains in the plate, including the transverse shear deformation effects. Polynomial functions that satisfy all the boundary conditions of the material system are used as trial functions. Comparison of these solutions to those first proposed by Nadai in 1925 revealed that additional terms are added to the original analysis (which used classical plate theory) to incorporate these effects. The methods developed clearly show the effects of the transverse shear deformation and are valid for any sandwich, laminate, or monocoque plate of any aspect ratio. Subsequent finite element and experimental analysis were conducted to verify the analytical study. Both the numerical and experimental results confirm that the analytical results are very good approximations for describing the linear deformation of the panels subject to in-plane shear loads.

Effects of In-Plane Shear Loads on Transverse Shear Deformations in Composite Panels

Laminated construction has many structural applications. However, in all such construction, structural reliability is predicated on the fact that the laminae remain joined together, otherwise many of the advantages of employing dissimilar materials together are lost. Questions then arise as to whether thin bonds, thick bonds, pliable bonds or stiff bonds should be used between laminae. Certainly it is very important to know the state of stresses throughout the bond to determine the bond material requirements. A detailed discussion of bonded joints and laminated construction could be a volume in itself. In this section, the simplest case of a laminated cylindrical isotropic shell is discussed in order to present all of the important considerations with a minimum of complexity. More complicated problems will be discussed in Part II of this text.

Laminated Shells and Adhesive Bonded Joints

Elastic Instability (Buckling) of Sandwich Plates

Just as in Chapter 4, which dealt with shells of revolution composed of isotropic materials, the same general approach can be used for shells of revolution composed of composite materials, following Daugherty [17.1].

Jack R. Vinson

Papers

Shells of Revolution Subjected to Axially Symmetric Loads

Effects of In-Plane Shear Loads on Transverse Shear Deformations in Composite Panels

Laminated Shells and Adhesive Bonded Joints

Elastic Instability (Buckling) of Sandwich Plates

Orthotropic Shells of Revolution Including Transverse Shear Deformation and Thermal Thickening