Fracture analysis of local delaminations in laminated composites

A shear deformation model was developed to analyze local delaminations growing from transverse cracks in 90 degree plies located around the mid plane of symmetric laminates. The predictions of the model agree reasonably with experimental data from T300/934 graphite epoxy laminates. The predicted behavior is such that, in combination with an edge delamination model, the critical loads can be predicted accurately in the range of n from .5 to 8

Introduction to the analysis of delamination related fracture processes in composites

This research concerns the analysis and prediction of delamination damage that occurs in composite structures on the sublaminate scale - that is, the scale of individual plies or groups of plies. The objective was to develop analytical models for fixed-mode delamination in composites. These include: (1) the influence of residual thermal and moisture strains; (2) local or transverse crack tip delamination originating at the tip of transverse matrix cracks; and (3) delamination in tapered composite under tensile loading. Computer codes based on the analytical models were developed and comparisons of predictions with available experimental and analytical results in the literature were performed

Cuando atacan los animales

Los cuentos de Alicia Erian han aparecido recientemente en Zoetrope y Nerve. Su primera colección de narrativa breve, The Brutal Language of Love, la publicará la editorial Villard el año próximo. Alicia Erian vive en brooklyn, Nueva York, con su marido, David Franklin. «Cuando atacan los animales» es el primero de sus relatos traducidos al español. Traductor: Juan Gabriel López Guix es traductor del inglés y francés. Se dedica sobre todo a la traducción de narrativa, ensayo y divulgación científica, así como a la traducción para prensa. Entre otros autores, ha traducido libros de Julian Barnes, Joseph Brodsky, Douglas Coupland, David Leavitt, Michel de Montaigne, Vikram Seth, George Steiner y Tom Wolfe. Es coautor de un Manual de traducción inglés-castellano (Gedisa, 1997)

Studies on some unsaturated organonitrogen metal systems

This thesis describes studies on the coordination chemistry and reactions with metal halides of some unsaturated organonitrogen compounds. The systems studied included various ketimines, R(^1)R(^2) C = NH, and derivatives thereof, R(^1)R(^2) C = NH, MX(_n) or R(^1)R(^2) C = NMX(_n-1) containing antimony or tin atoms attached to the imino-nitrogen atoms. Aspects of the coordination chemistry of acrylonitrile CH(_2) : CHC : N and its methyl derivatives, CH(_2) : CMe C : N and MeCH : CH C : N have also been studied as well as their reactions with ether/SnCℓ(_2)/HCℓ systems. The main feature studied in the imine work was the tendency of compounds (4-XC(_6)H(_4))(_2)C = NSbCℓ(_n) (X = H or Me, n = 2 or 4) to undergo cyclometallation reaction forming a new type of antimony ring compound; 2 - SbCℓ(_n) – 4 – XC(_6)H(_3)C(4 – XC(_6)H(_4)) – NH. Related cyclometallation reactions are surveyed in chapter 1. During attempts to prepare other diarylketimino antimony tetrachlorides such as o-tolyl, ph C = NSbCℓ(_4); m-tolyl, ph C = NSbCℓ(_4) and (4 – FC(_6)H(_4))(_2) C = NSbCℓ(_4), no analogous cyclometallated products were obtained. Instead two different products were isolated: Aryℓ(_2)CNH(^+)(_2)SbCℓ(^-)(_4) and Aryℓ(_2)CNH(^+)(_2)SbCℓ(^-)(_6). Attempts to prepare t-butyl derivatives of general formula Ar, Bu(^t) C = NSbCℓ(_4) (Ar = o-tolyl, p-tolyl; m-tolyl) afforded arylnitrile, HCℓ and SbCℓ(_3), probably by elimination of Me(_2)C = CH(_2). Chloroform solutions of diphenylketimine and antimony penta- or tri- chloride deposited ph(_2)CNH(^+)(_2) SbCℓ(^-)(_6) or (ph(_2)CNH(^+)(_2))(_2) SbCℓ(_5)(^2-) respectively. In the nitrile work, using ether/SnCℓ(_2)/HCℓ systems which contain R(_2)OH(^+). SnCℓ(_3)(^-) and (R(_2)O(^+)H)(_2) ∙ SnCℓ(_4)(^2-), addition to the C = C bond of the acrylonitrile yielded Cℓ(_3)Sn.CK(_2).CH(_2).CN. Methacrylonitrile and crotononitrile gave more complicated reactions with ether/SnCℓ(_2)/HCℓ systems, apparently undergoing dimerization to form amidinium cations containing C = N - CR = NH(_2)(^+) units. Finally, several complexes were isolated from reactions between acrylonitrile or its methyl derivatives and the metal chlorides TiCℓ(_4), SnCℓ(_4), SbCℓ(_5), BCℓ(_3) CoCℓ(_2), ZnCℓ(_2), TiBr(_4), TaCℓ(_5), NiCℓ(_2)/2SbCℓ(_5) and NiCℓ(_2)/2ZnCℓ(_2). Spectroscopic and conductivity studies of these complexes were carried out, and used to deduce their probable structures

Analysis of delamination related fracture processes in composites

This is a final report that summarizes the results achieved under this grant. The first major accomplishment is the development of the sublaminate modeling approach and shear deformation theory. The sublaminate approach allows the flexibility of considering one ply or groups of plies as a single laminated unit with effective properties. This approach is valid when the characteristic length of the response is small compared to the sublaminate thickness. The sublaminate approach was validated comparing its predictions with a finite element solution. A shear deformation theory represents an optimum compromise between accuracy and computational effort in delamination analysis of laminated composites. This conclusion was reached by applying several theories with increasing level of complexity to the prediction of interlaminar stresses and strain energy release rate in a double cracked-lap-shear configuration

A finite-element-based perturbation model for the rotordynamic analysis of shrouded pump impellers: Part 1: Model development and applications

This study concerns the rotor dynamic characteristics of fluid-encompassed rotors, with special emphasis on shrouded pump impellers. The core of the study is a versatile and categorically new finite-element-based perturbation model, which is based on a rigorous flow analysis and what we have generically termed the 'virtually' deformable finite-element approach. The model is first applied to the case of a smooth annular seal for verification purposes. The rotor excitation components, in this sample problem, give rise to a purely cylindrical, purely conical, and a simultaneous cylindrical/conical rotor whirl around the housing centerline. In all cases, the computed results are compared to existing experimental and analytical data involving the same seal geometry and operating conditions. Next, two labyrinth-seal configurations, which share the same tooth-to-tooth chamber geometry but differ in the total number of chambers, were investigated. The results, in this case, are compared to experimental measurements for both seal configurations. The focus is finally shifted to the shrouded-impeller problem, where the stability effects of the leakage flow in the shroud-to-housing secondary passage are investigated. To this end, the computational model is applied to a typical shrouded-impeller pump stage, fabricated and rotor dynamically tested by Sulzer Bros., and the results compared to those of a simplified 'bulk-flow' analysis and Sulzer Bros.' test data. In addition to assessing the computed rotor dynamic coefficients, the shrouded-impeller study also covers a controversial topic, namely that of the leakage-passage inlet swirl, which was previously cited as the origin of highly unconventional (resonance-like) trends of the fluid-exerted forces. In order to validate this claim, a 'microscopic' study of the fluid/shroud interaction mechanism is conducted, with the focus being on the structure of the perturbed flow field associated with the impeller whirl. The conclusions of this study were solidified by the outcome of a numerical-certainty exercise, where the grid dependency of the numerical results is objectively examined. The final phase of the shrouded-impeller investigation involves the validation of a built-in assumption, in all other perturbation models, whereby single-harmonic tangential distributions of all the flow thermophysical properties are imposed. The last phase of the investigation course is aimed at verifying the fine details of the perturbed flow field in light of recent set of detailed LDA measurements in a smooth annular seal. Grid dependency of the fluid-induced forces is also investigated, and specific recommendations are made

Analysis of delamination related fracture processes in composites

An anisotropic thin walled closed section beam theory was developed based on an asymptotical analysis of the shell energy functional. The displacement field is not assumed a priori and emerges as a result of the analysis. In addition to the classical out-of-plane torsional warping, two new contributions are identified namely, axial strain and bending warping. A comparison of the derived governing equations confirms the theory developed by Reissner and Tsai. Also, explicit closed form expressions for the beam stiffness coefficients, the stress and displacement fields are provided. The predictions of the present theory were validated by comparison with finite element simulation, other closed form analyses and test data