Jack R. Vinson

Bio: Jack R. Vinson is an academic researcher from University of Delaware. The author has contributed to research in topics: Shell (structure) & Sandwich-structured composite. The author has an hindex of 30, co-authored 168 publications receiving 8303 citations.

Computer program for calculating the stresses in shallow spherical shells of composite materials subjected to localized loads.

Abstract: : The computer program listed can be used to calculate the stresses anddeflections in a specially orthotropic shallow or nonshallow spherical shellof revolution subjected to a normal concentrated load in the apex region ofthe shell. The effect of transverse shear deformation is included suchthat any ratio of elastic modulus/shear modulus is possible. The programis written in ASA FORTRAN IV compatible with the scientific data system9300 computer. (Author, modified-PL)

Strength and Failure Theories

Abstract: In the past sections we have focused upon the functional requirements of beam, plate and shell structural elements as subjected to particular loading environments. The material presented in this section now addresses the broader based objective of having acquired a knowledge of the load analysis methodology, how can one now apply this knowledge to design a structural system to ensure a potentially safe design.

Continued Efforts in the Development of Piezo-Activated Composite Sandwich Fins

Abstract: Over the past four years, the University of Delaware's Center for Composite Materials and the US Army Research Laboratory have spearheaded a team of researchers developing piezo-electrically actuated smart fins for use in the guidance and control of surface-to- surface projectiles as well as other military related applications. This project has undergone several iterations yielding a current design consisting of a piezoelectric sandwich structure potted into a steel spar and behaving as a cantilevered thin panel. The Macro Fiber Composites (MFC's) technology developed by NASA, make the current sandwich design feasible. With one MFC patch adhesively bonded to each side of a thin host panel, controlled angular deflection is achieved by electrically activating each of the patches. The most recently achieved milestone for the project involved demonstrating the feasibility of the thin panel design. The results of these feasibility demonstrations, as well as the foundational theories and principles, have been presented in various formats to include the 2005 AIAA conference. The current focus of the project has been on better characterizing the existing fins and increasing the understanding of their behavior, all with a view towards increasing the performance of these fins in a real, load-bearing environment. To help remedy this situation as well as provide a basis for improved performance, increased laboratory capabilities have been coupled with experimentation to provide insight into the following areas: parameter based sensitivity analysis, torque vs. deflection analysis, hysteresis, and potential for control. The theoretical sensitivity analysis performed examined the change in the free deflection, stiffness, and force generated due to alterations in various design variables to include the thickness and modulus of elasticity of the MFC patches, adhesive layers, and host material, as well as other parameters. This analysis indicates that a thinner host material with a greater modulus of elasticity should yield a sandwich structure capable of achieving greater deflection without sacrificing either the stiffness or the force generating capabilities. To serve as a basis for comparison, applied torque vs. achievable deflection curves have been produced for many of proposed structure designs. These torque deflection curves play a major part in both the decision making process as to what designs to manufacture, as well as comparing the performance of the manufactured fins.

Cellulose nanomaterials review: structure, properties and nanocomposites

Abstract: 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).

Use of piezoelectric actuators as elements of intelligent structures

Abstract: 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.

Review: current international research into cellulose nanofibres and nanocomposites

Abstract: 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.

Numerical experiments in revisited brittle fracture

Abstract: 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.