A study of the mechanical properties of liquid crystal polymer fibres and their adhesion to epoxy resin using Laser Raman Spectroscopy

PhDA number of high performance fibres (aramid, PBZT and PBO) spun from liquid crystal polymer solutions were examined in this work. In particular, a thorough investigation of the mechanical response of these fibres under tensile and compressive deformations was carried out. The major experimental tool employed was the technique of Laser Raman Spectroscopy. It was found that stress-induced changes of these fibres at molecular level are proportional to the macroscopic deformation applied. This correlation is unique for the fibres. A method for converting spectroscopic data to predicted stress-strain curves in tension and compression was proposed. An estimation of their compressive strength was derived and an understanding of the nature of their compressive failure was discussed. The adhesion of these fibres to epoxy resin was also investigated by monitoring in situ the interfacial stresses developed along the interface/interphaseo f model single fibre composite coupons. The strength of the interfacial bond was measured. The effect of various parameters such as fibre modulus, fibre diameter and fibre nature upon the interfacial strength of the various systems was evaluated. The mechanisms of stress transfer along with the nature of interfacial damage was examined accurately. It was found that the major parameter controlling the above mechanisms was interfacial yielding in shear. A numerical appoximation (using Finite Element Analysis) was employed in order to evaluate the experimental results. Finally, general conclusions concerning the performance of these fibres were drawn.Pateras Foundation of Scholarshi

Active vibration control of a space truss using a lead zirconate titanate stack actuator

This paper presents design, implementation and experimental results of active vibration control of Naval Postgraduate School (NPS) space truss using a piezoelectric ceramic stack actuator. The NPS space truss represents a flexible spacecraft structure that may support interferometer, antenna and other vibration-sensitive instrumentation. To simulate the effects of a spacecraft disturbance on the truss, a proof mass actuator is incorporated on the structure to excite the truss. To reduce the vibrations caused by the proof mass actuator, an active strut member is installed along a diagonal of the base bay of the truss. The active strut element consists of a piezoelectric ceramic actuator stack, a force transducer and mechanical interfaces. An integral plus double-integral force controller is designed to suppress vibration of the truss. Experimental results demonstrate that the active piezoceramic strut actuator can effectively reduce truss vibration

A study of the mechanical properties of liquid crystal polymer fibres and their adhesion to epoxy resin using laser Raman spectroscopy

SIGLEAvailable from British Library Document Supply Centre-DSC:DXN005121 / BLDSC - British Library Document Supply CentreGBUnited Kingdo

Studies in steroids and alkaloids

In part I of this thesis are described our studies in the area of aza steroids. These investigations involve chemical and spectroscopic studies of these compounds. Lithium aluminum hydride reduction of 3β-hydroxy-11-aza-5a, 22β-spirost-8(9)-en-12-one (72) provides the enamine, (73), which upon subsequent conversion to its iminium salt, (75), and borohydride reduction yields 11-aza-5a, 8ξ, 9a, 22β-spirostan-3β-o1 (76). This reaction furnishes a convenient sequence for reduction of the 8, 9-double bond in 11-aza steroid derivatives. Degradation of the sapogenin side chain then allows entry into 11-aza pregnane derivatives. The synthetic sequence provides the first examples of 11-aza steroid analogues in which ring C is six-membered and completely saturated. A detailed discussion of the mass spectra of 6- and 11-aza steroid derivatives is presented. In part II of this thesis is described our work which relates to a synthetic approach to the Iboga and Aspidosperma alkaloids. The first section involves the synthesis of 2-carbomethoxy-3-[a-hydroxy-β-(3-carbomethoxy-N-piperidyl)-ethyl]-indole (78) and 3-[β-(3-carbomethoxy-N-piper-dyl)-ethyl]-indole-2-acetic acid methyl ester (93). The Hoesch reaction was used for the synthesis of 2-carbomethoxy-3-chloroacetylindole (75) from 2-carbomethoxy-indole (74) and chloroaceto-nitrile. Treatment of 75 with 3-carbomethoxy piperidine (76) yielded 2-carbomethoxy ‒3 ‒ (3-carbomethoxy-N-piperidyl)-acetylindole (77). The latter compound was reduced with sodium borohydride or by catalytic hydrogenation with Raney nickel to 78. Prolonged hydrogenation of 77 or 78 with Raney nickel catalyst provided 2-carbomethoxy-3-[a-hydroxy-β-(3-carbomethoxy-N-piperidyl)-ethyl]-4, 5, 6, 7-tetrahydro-indole (79). Similarly 2-carbomethoxy-indole (74) was reduced to 2-carbomethoxy-4, 5, 6, 7-tetrahydro- indole (80) by hydrogenation with platinum oxide catalyst. The Hoesch reaction was also used for the synthesis of 3-chloro-acetylindole-2-acetic acid methyl ester (89) from indole-2-acetic acid methyl ester (88) and chloroacetonitrile. Treatment of 89 with 2-carbomethoxy piperidine (76) provided 3-(3-carbomethoxy-N-piperidyl)-acetyl-indole-2-acetic acid methyl ester (92). The latter substance was reduced with diborane to 93. The second section provides the synthesis of 1, 2 , 3, 5, 6, 11, 11b (ξ)-heptahydro-2ξ-(ɜ-chloropropyl)-2ξ-ethyl-3-oxo-indolo(2, 3-g)indolizine (118). The fundamental reaction involved condensation of tryptamine with either ethyl a-keto-ʏ-(ʏ-benzyloxypropyl)-ʏ-ethyl-glutarate (70b) or ethyl-a-(ʏ-benzyloxypropyl)-a-ethyl-syccinate (70a). When glutarate 70b was condensed with tryptamine the amides 110 and 111 were obtained. On the other hand, the succinate 70a reacted with tryptamine to afford the desired N-[β- (3-indolyl)-ethyl-a- (ʏ-benzyloxypropyl)-a-ethyl-succinimide (112). Treatment of the latter substance with boron tribromide yielded N-[β-(3-indolyl)-ethyl]-a-(3-hydroxypropyl)-a-ethyl-succinimide (115), which was subsequently converted to N-[β-(3-indolyl)-ethyl]-a-(3-chloropropyl)-a-ethyl-succinimide (116) with thionyl chloride. Cyclization of the latter substance with phosphorus pentoxide afforded 2, 3, 5, 6, 11-pentahydro-2ξ-(3-chloropropyl)-2ξ-ethyl-3-oxo-indolo(2, 3-g) indolizine (117), which on hydrogenation with platinum oxide yielded 118. The glutarate 70b and the succinate 70a involved in the above syntheses were obtained via a series of established reactions, starting from benzyl ʏ-chloropropyl ether (101).Science, Faculty ofChemistry, Department ofGraduat

Synthesis of aza steroids. Part I. The synthesis of 6-aza steroids. Part II. The synthesis of 11-aza steroids

Ozonization of 7-ketocholesteryl acetate has yielded methyl 5-keto-5, 7-seco-6-nor-3-cholestene-7-oate in reasonably high yield. This intermediate was converted by catalytic hydrogenation to methyl-5-keto-5, 7-seco-6-norcholestan-7-oate which upon treatment with benzyl amine gave N-benzyl-6-aza-4-cholesten-7-one.Science, Faculty ofChemistry, Department ofGraduat