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The problem with which this investigation is concerned is that of identifying and prioritizing the competencies required to design and implement manufacturing systems for advanced composite structures. The classical Delphi procedure is the research method used for the conduct of this study. A five-member advisory board developed a list of seventeen categories under which the competencies would reside. In the first-round questionnaire, the seventeen categories were presented to a Delphi panel of experts who provided up to five competencies required in each category. The first-round returns provided two new categories and 973 competency statements. Duplications were eliminated and 366 competency statements remained in nineteen categories. The second, third, and fourth rounds were a reiterative rating process. The panel was asked to rate the items in the questionnaire based on their relative importance to the intent of the study. The importance rating scale included "very important," "important," "slightly important," and "unimportant." The means and interquartile ranges were calculated for each statement and provided as feedback in the successive round. Kendall's coefficient of concordance W for tied ranks was used to validate the panel consensus. The W was significant at the .01 level for each of the three rounds where rating was performed. The data were presented in rank order within categories by importance level. Eighteen percent of the competency statements were rated "very important," 77 percent "important, and 5 percent "slightly important." No statements were rated "unimportant" by the panel. It was concluded that, as indicated by the 19 categories and 366 competencies, the scope of the requirements for designing and implementing manufacturing systems for advanced composite structures represent a broad range of knowledge and skill requirements. The breadth of the range of the requirements indicated the need for the development of areas of specialization within the subject field to adequately address the requirements.

The load-deflection behavior of a US Army Corps of Engineers available sandwich plates in three-point bending with glass phenolic facings and balsa wood core is being investigated under room and elevated temperatures. Test data on bending rigidity, critical interfacial failure (skin-to-core interface) and shear stress are collected and analyzed. The load-deflection curves plots up to the point of failure initiation are being studied. The effects of the span and the radius of the loading nose on the bending modulus and strength are examined systematically. Theoretical calculations from a modified beam theory of sandwich structure are applied and the effect of the shearing rigidity of the core is studied, and the propensity with respect to the span is also investigated. A finite element model is developed to study the flexural and stress analysis. Based on the results, this thesis proposes a desirable analytical approach that correlates theory with experiment as defined below.

Cardiovascular diseases are the leading causes of death globally. One contributing factor that can lead to heart failure is a myocardial infarction. When an infarct occurs, an occlusion in the tissue vasculature prevents blood flow beyond this site. It results in scar tissue formation. The scar is non-contractile and reduces the working efficiency of the heart. To compensate, left ventricular remodeling will ensue resulting in enlarging of the left ventricle. This progression of events ultimately culminates in heart failure. One approach to assist patients who have suffered a heart attack is to implant a cardiac patch. Current patches are acellular and aim to retain the geometry of the left ventricle, limiting any ventricular remodeling from occurring. While these patches provide a passive support, it is hypothesized that incorporation of cells into the patches could result in functional support that could help to restore baseline function. To be effective, a cell-populated cardiac patch would need to integrate with the host tissue functionally and mechanically. In this thesis, we developed a fibrin microthread-based composite scaffold with material properties comparable to left ventricular myocardium that promotes regional cardiomyocyte alignment and physiologically relevant contractile strains. We hypothesized that a composite material could be developed where constituents of the material would complement one another to yield a mechanically reinforced scaffold that promotes cardiomyocyte function. Through manipulation of the volume fraction of the components, we manipulated the modulus of the layer without compromising contractile strain or contractile frequency of incorporated cells. Additionally, through strategic restraint of the scaffolds, we utilized cell-mediated compaction to induce a tension pattern that increased alignment of incorporated cells. This corresponded to an increase in contractile strain magnitudes, and an anisotropic contractile wave propagation through the engineered tissue. Finally, we laminated composite layers into a patch mimicking the architecture of ventricular myocardium and found that material properties of the patch were similar to properties of the target tissue. In summary, we designed a biomimetic composite patch with material properties similar to ventricular myocardium that supports cardiomyocyte alignment and contractility to promote functional and mechanical integration upon implantation.

Student Number : 0001361N - MSc(Eng) dissertation - School of Mechanical, Industrial and Aeronautical Engineering - Faculty of Engineering and the Built Environment / Thick composite cylinders are important structural elements which cannot be analysed by traditional techniques due to through-thickness effects. This work presents analyses for thick composite tubes of finite length including through-thickness shear. A numerical thermal analysis is implemented for the determination of the transient through-thickness behaviour of tubes. A me- chanical analysis, based on the Rayleigh-Ritz technique, is presented which analyses finite length, composite tubes under a variety of loadings. The anal- yses are shown to be accurate and efficient and are validated against existing results. Results are presented for two ring-stiffened tubes under pressure and thermal loading and also for the transient thermal behaviour of these tubes. It was found that both the through-thickness and transient effects are of im- portance as the stress variation through the thickness and with time was significant for both tubes.

Seet Wah Cheong. / Thesis (M.Phil.)--Chinese University of Hong Kong, 1994. / Includes bibliographical references (leaves 78-81). / Acknowledgement --- p.i / Abstract --- p.ii / Chapter 1 --- Introduction --- p.1 / Chapter 2 --- Perturbation approach and Effective Medium Approximation --- p.6 / Chapter 2.1 --- Perturbation method of calculating local fields --- p.6 / Chapter 2.1.1 --- Formalism --- p.7 / Chapter 2.1.2 --- Results of the perturbation calculations of potentials --- p.10 / Chapter 2.2 --- Effective Medium Approximation (EMA) --- p.13 / Chapter 2.2.1 --- Self-consistency conditions --- p.14 / Chapter 2.2.2 --- Results from the self-consistency conditions --- p.14 / Chapter 2.2.3 --- A simplified version of EMA --- p.16 / Chapter 2.3 --- Conclusion --- p.19 / Chapter 3 --- Dilute limit : Enhancement due to surface plasmon resonance --- p.20 / Chapter 3.1 --- Formalism --- p.21 / Chapter 3.2 --- Models and results --- p.25 / Chapter 3.2.1 --- Nonlinear spherical metallic inclusion --- p.25 / Chapter 3.2.2 --- Shell model with nonlinear core --- p.26 / Chapter 3.2.3 --- Shell model with nonlinear shell --- p.28 / Chapter 3.3 --- Conclusion --- p.30 / Chapter 4 --- Numerical calculations of electric potential --- p.32 / Chapter 4.1 --- Formalism --- p.33 / Chapter 4.2 --- Results --- p.41 / Chapter 4.3 --- Symbolic simulations --- p.43 / Chapter 4.3.1 --- Formalism --- p.43 / Chapter 4.3.2 --- Results --- p.45 / Chapter 4.4 --- Conclusion --- p.45 / Chapter 5 --- Local field enhancement in nonlinear composites of multiply coated spherical inclusion --- p.46 / Chapter 5.1 --- Formalism --- p.47 / Chapter 5.2 --- Single spherical inclusion --- p.49 / Chapter 5.3 --- Single shell particle inclusion --- p.50 / Chapter 5.4 --- Nonlinear problem --- p.50 / Chapter 5.5 --- Core field in the single sphere --- p.52 / Chapter 5.6 --- Summary --- p.55 / Chapter 6 --- Optical transition and random resistor network --- p.57 / Chapter 6.1 --- Formalism --- p.58 / Chapter 6.1.1 --- Model --- p.58 / Chapter 6.1.2 --- Solution of the model --- p.60 / Chapter 6.1.3 --- EMA --- p.61 / Chapter 6.1.4 --- Optical transition --- p.62 / Chapter 6.1.5 --- Scaling functions --- p.63 / Chapter 6.2 --- Random resistor network simulation --- p.64 / Chapter 6.2.1 --- One sample frequency dependence --- p.64 / Chapter 6.2.2 --- Sample averages --- p.66 / Chapter 6.3 --- Nonlinear EMA calculations of optical transition --- p.67 / Chapter 6.4 --- Symbolic calculation of conductivities in small h expansion --- p.69 / Chapter 6.4.1 --- Formalism --- p.69 / Chapter 6.4.2 --- Finite size scaling and exponents --- p.71 / Chapter 6.4.3 --- Scaling Function expansion coefficients --- p.74 / Appendix Estimation of surface plasmon resonance frequency --- p.76 / Chapter A.1 --- Single nonlinear metallic sphere --- p.76 / Chapter A.2 --- "Single metallic shell, nonlinear core model" --- p.77 / Bibliography --- p.78 / Figure Caption --- p.82 / List of Tables --- p.91

Resin-composites have been used in dentistry as direct restorative materials for over fifty years ago, and meanwhile their properties have been substantially improved. Recently a new class of light-cured resin-composites known as 'bulk-fill' materials has been introduced, and has increased the practical application of resin-composites in comparison to conventional incrementally applied materials. The aim of the present research was to assess bulk-fill resin-composites in comparison to conventional materials with respect to their composition, polymeric structure properties and hygroscopic behaviour in oral and food simulating substances. A variety of bulk-fill and conventional resin-composites were tested in this study. Monomer composition of materials has been qualitatively and quantitatively determined using high performance liquid chromatography and mass spectroscopy, and their degree of conversion assessed using Fourier transform infrared spectroscopy. It was found that the degree of conversion of the bulk-fill resin-composites was generally comparable to that of conventional materials and appeared to be governed by the type and quantity of monomers comprising the resin matrix. To evaluate the cross-link density of the polymer matrix, the extent of post-irradiation hardness development, chemical softening, and thermal stability were assessed using microhardness and thermogravimetric analysis. Materials showed variable results and it was suggested that two networks were present in the polymerized resin matrix, a primary network forming immediately after curing followed by a secondary network. The secondary network seemed to have poor cross-link density with low resistance to the degradative effects of solvents. Monomer elution from cured materials was assessed using High performance liquid chromatography over three months' storage in three different media. Elution from bulk-fill resin-composites was found to be comparable to that of conventional materials, despite their increased incremental thickness, with remarkably minimal elution taking place from two bulk-fill materials examined. Monomer elution was shown to be highly dependent on the hydrophobicity of the base monomers and the network characteristics of the resin-matrix. UDMA-BisEMA based systems appeared to be more vulnerable in organic solutions than BisGMA and BisGMA-BisEMA based systems in terms of monomer elution. Sorption and solubility were assessed after one years' storage in water and artificial saliva. Water sorption and solubility of resin-composites were material-dependent and highly affected by the filler loading and initial degree of conversion of the polymeric matrix. BisEMA and UDMA-BisEMA based polymer networks appeared to be more hydrophobic and resistant to sorption and solubility than BisGMA based systems in water based media. The bulk-fill and conventional resin-composites tested were considered stable in the long-term water storage, with the exception of one conventional flowable material.

Increasing worldwide environmental awareness is encouraging scientific research into the development of cheaper, more environmentally friendly and more sustainable construction and packaging materials. Natural fibre reinforced thermoplastic composites are strong, stiff, lightweight and recyclable, and have the potential to meet this need. Industrial hemp fibre is amongst the strongest of the natural fibres available, and possesses a similar specific stiffness to E-glass, but with additional benefits such as low cost and low production energy requirements. The favourable mechanical properties of hemp, however, have yet to be transferred successfully to thermoplastic-matrix composite materials. The aim of this thesis was to achieve a greater understanding of the various parameters that contribute to composite strength and stiffness, and to manipulate these parameters in order to produce an improved hemp fibre reinforced polypropylene composite material. Hemp fibre was alkali treated at elevated temperatures in a small pressure vessel with either a solution of 10wt% NaOH or 5wt% NaOH / 2wt% Na2SO3. Single fibre tensile tests were performed on treated and untreated fibres, and it was found that the NaOH/Na2SO3 treatment produced the strongest and stiffest fibres with a good level of fibre separation. Lignin tests revealed that both alkali treatments were effective in the removal of lignin from hemp fibre, and XRD analysis showed that both alkali treatments resulted in increases in the hemp fibre crystallinity index. TGA and DTA analysis showed that the alkali fibre treatments improved the thermal stability of the treated hemp fibre when compared to the untreated fibre. Alkali treated hemp fibre, polypropylene and a maleic anhydride modified polypropylene (MAPP) coupling agent were compounded in a twin-screw extruder, and injection moulded into composite tensile test specimens. A range of composites with different fibre and MAPP contents were produced and tested. Tensile tests revealed that the optimum composite consisted of polypropylene with 40wt% NaOH/Na2SO3 treated hemp fibre and 4wt% MAPP, and had a tensile strength of 50.5 MPa and a Young's modulus of 5.31 GPa, respectively. The effect of MAPP on the fibre/matrix interface of NaOH/Na2SO3 treated hemp fibre/polypropylene composites was assessed by means of the single fibre fragmentation test. A composite consisting of NaOH/Na2SO3 treated fibres in a matrix of 4wt% MAPP and polypropylene was found to have a critical fibre length of 0.83mm and an interfacial shear strength of 16.1 MPa. The effects of MAPP on the composite fracture mechanisms were evaluated by means of SEM microscopy. TGA and DTA analysis showed that untreated hemp fibre composites and NaOH/Na2SO3 treated hemp fibre composites, each with a matrix of 4% MAPP and polypropylene, were less thermally stable than the polypropylene matrix alone. The Bowyer-Bader model was used to model the strength of an injection moulded composite with a normal fibre length distribution, consisting of 40wt% NaOH/Na2SO3 treated fibre, 4% MAPP and polypropylene. A theoretical composite tensile strength of 149 MPa was obtained from the model, based on the assumption that all the fibres were axially aligned in the composite. Composites with long, axially aligned fibres were produced using a novel solution mixing technique, where the polymer matrix and MAPP coupling agent were dissolved in a solvent and then precipitated inside an aligned fibre mat. Significant improvements in tensile strength and Young's modulus were achieved for solution mixed composites compared to composites produced by means of extrusion and injection moulding. The strongest solution mixed composite had a tensile strength of 84.7 MPa, and consisted of 56wt% NaOH/Na2SO3 treated fibre, 4% MAPP and polypropylene; and the stiffest injection moulded composite had a Young's modulus of 16.0 GPa, and consisted of 63wt% NaOH/Na2SO3 treated fibre, 4% MAPP and polypropylene.