Criterion for mixed mode fracture in composite bonded joints

A study was undertaken to characterize the debond growth mechanism of adhesively bonded composite joints under mode I, mixed mode I-II, and mode II static loadings. The bonded system consisted of graphite-epoxy composite adherends bonded with a toughened epoxy adhesive. The mode I, mode II and mixed mode I-II fracture energies of the tested adhesives were found to be equal to each other. The criterion for mixed mode fracture in composite bonded joints was found

Finite element analysis of end notch flexure specimen

A finite element analysis of the end notch flexure specimen for mode II interlaminar fracture toughness measurement was conducted. The effect of friction between the crack faces and large deflection on the evaluation of G sub IIc from this specimen were investigated. Results of this study are presented in this paper

Mixed-mode cyclic debonding of adhesively bonded composite joints

A combined experimental-analytical investigation to characterize the cyclic failure mechanism of a simple composite-to-composite bonded joint is conducted. The cracked lap shear (CLS) specimens of graphite/epoxy adherend bonded with EC-3445 adhesive are tested under combined mode 1 and 2 loading. In all specimens tested, fatigue failure occurs in the form of cyclic debonding. The cyclic debond growth rates are measured. The finite element analysis is employed to compute the mode 1, mode 2, and total strain energy release rates (i.e., GI, GII, and GT). A wide range of mixed-mode loading, i.e., GI/GII ranging from 0.03 to 0.38, is obtained. The total strain energy release rate, G sub T, appeared to be the driving parameter for cyclic debonding in the tested composite bonded system

A computer program for the determination of the acoustic pressure signature of helicopter rotors due to blade thickness

A computer program is presented for the determination of the thickness noise of helicopter rotors. The results were obtained in the form of an acoutic pressure time history. The parameters of the program are the rotor geometry and the helicopter motion descriptors, and the formulation employed is valid in the near and far fields. The blade planform must be rectangular, but the helicopter motion is arbitrary; the observer position is fixed with respect to the ground with a maximum elevation of 45 deg above or below the rotor plane. With these restrictions, the program can also be used for the calculation of thickness noise of propellers

Fatigue behavior of adhesively bonded joints

The fatigue damage mechanism of composite to composite adhesively bonded joints was characterized. The mechanics of the possible modes of fatigue damage propagation in these joints when subjected to constant amplitude cyclic mechanical loading were investigated. The possible failure modes in composite bonded joints may be cyclic debonding (i.e., progressive separation of the adhesive), interlaminar damage (delamination), adherend fatigue or a combination of these. Two composite systems - graphite/epoxy adhesively bonded to graphite/epoxy and Kevlar 49/epoxy adhesively bonded to Kevlar 49/epoxy were investigated. Both composite systems consisted of quasi-isotropic lay-ups, i.e., 0 deg/-45 deg/+45 deg/90 degs. The two adhesives, employed in the study were (1) EC 3445 with cure temperature of 250 F for secondary bonding and (2) FM 300 with cure temperature of 350 F for co-cure bonding

Révolution, traumatisme et non-savoir : la « longue surprise » dans Le nouveau Paris de Mercier

Le nouveau Paris (1798) de Louis Sébastien Mercier est principalement consacré à la Révolution française dont l’auteur fut, selon ses termes, « témoin, acteur et victime ». Le traitement du traumatisme personnel et collectif qu’a été la Terreur est ici caractérisé par une insistance sur l’aveuglement et la désorientation de tous les participants, sur leur « longue surprise ». Mercier estime que les héritiers de la Révolution ne comprendront pas ce qui a été réellement vécu pendant cette période, cet état vertigineux de non-savoir. L’acquis politique cependant (« Je suis né sujet ; je mourrai républicain ») est une force qui permet à l’auteur d’accepter cette incompréhension traumatique, telle qu’elle a été vécue et telle qu’elle est pressentie.Le nouveau Paris (1798) by Louis Sébastien Mercier is mainly devoted to the French Revolution, during which the author was, in his own words, « a witness, a participant and a victim ». What characterizes his treatment of the Reign of Terror — a personal and a collective trauma — is his insistance on the blindness and the disorientation of all involved. Moreover, Mercier believes that future generations will not understand what was actually experienced during that period, in particular the permanent state of « not-knowingness ». The political gain of the Revolution (« I was born a subject ; I shall die a Republican »), though, gives the writer the strength to accept this traumatic incomprehension, both as it was experienced and as it is anticipated

Fish and bivalves at Bolsa Chica Marsh re-establishment project; Progress report III

The objectives of our fish and bivalve study are: 1. Determine changes in the number of species of fish and bivalves before Phase I and during Phase 1 at Bolsa Chica Marsh. 2. Determine if California Department of Fish and Game's predicted benefits in Phase I were achieved by increases in fish species. 3. Determine influences of water management practices upon fish and bivalve composition. Thirteen species of fish and five species of bivalves were collected from Inner Bolsa Bay and South Bolsa Slough. Deepbody anchovy, Anchoa compressa; jacksmelt, Atherinopsis californiensis; longjaw mudsucker, Gillichthys mirabilis; specklefin midshipman, Porichthys myriaster; round stingray, Urolophus halleri; banded chione, Chione californiensis; bentnose clam, Macoma nasuta; and common littleneck clam, Protothaca staminea have not been reported previously from Inner Bolsa Bay. Nine species of fish and four species of bivalves were collected from outer Bolsa Bay. Yellowfin goby, Acanthogobius flavimanus; longjaw mudsucker; tilapia, Tilapia mossambica; and bay pipefish, Syngnathus leptorhynchus have not been reported previously from Outer Bolsa Bay. (11pp.

Student Experience: Surabhi Mall, MSc Development Management 2012/13

I am a graduate from the LSE MSc Development Management course (2012-13)

Measurement of viscosity of gaseous mixtures at atmospheric pressure

Coefficients of viscosity of various types of gas mixtures, including simulated natural-gas samples, have been measured at atmospheric pressure and room temperature using a modified capillary tube method. Pressure drops across the straight capillary tube section of a thermal mass flowmeter were measured for small, well-defined, volume flow rates for the test gases and for standard air. In this configuration, the flowmeter provides the volumetric flow rates as well as a well-characterized capillary section for differential pressure measurements across it. The coefficients of viscosity of the test gases were calculated using the reported value of 185.6 micro P for the viscosity of air. The coefficients of viscosity for the test mixtures were also calculated using Wilke's approximation of the Chapman-Enskog (C-E) theory. The experimental and calculated values for binary mixtures are in agreement within the reported accuracy of Wilke's approximation of the C-E theory. However, the agreement for multicomponent mixtures is less satisfactory, possible because of the limitations of Wilkes's approximation of the classical dilute-gas state model