Papers by Sirina Putthanarat
RESUMEN En este artículo se muestran las bases teóricas y el desarrollo de un algoritmo para el c... more RESUMEN En este artículo se muestran las bases teóricas y el desarrollo de un algoritmo para el cálculo de áreas totales de excavación (corte) y relleno (terraplén) de una sección transversal de construcción de una carretera. El desarrollo parte de la conceptualización de la sección transversal como una superposición de dos perfiles definidos mediante puntos (x,y): Un perfil representa el terreno natural y el otro representa la sección de construcción de la carretera. Se aplican conceptos de cálculo integral y funciones discretas para la identificación de figuras simples que hagan práctica la obtención de las áreas totales y su implementación en un programa de un paquete computacional. El resultado final es una serie de pasos descritos que se pueden programar en cualquier lenguaje de computadora que soporte arreglos, listas ligadas o colecciones de datos. Se hace énfasis en la obtención del algoritmo tomando como base las ciencias básicas que forman parte de las licenciaturas en ingeniería, con el fin de mostrar a los lectores que comienzan a estudiar una carrera en ingeniería que un procedimiento que se utiliza en la práctica profesional tiene como base los conocimientos que se adquieren en los inicios de estas licenciaturas. Finalmente se hacen recomendaciones y sugerencias para la extensión de utilización de este algoritmo en la construcción de plataformas de terracerías. Palabras Clave: Cuantificación de carreteras, secciones transversales de carreteras, Algoritmos para carreteras.
51st AIAA/ASME/ASCE/AHS/ASC Structures, Structural Dynamics, and Materials Conference<BR> 18th AIAA/ASME/AHS Adaptive Structures Conference<BR> 12th, 2010
Damage progression in laminated Overheight Compact Tension specimens was modeled using discrete r... more Damage progression in laminated Overheight Compact Tension specimens was modeled using discrete representations of individual cracks and delaminations. Matrix cracking and delamination initiation, propagation, and interaction, without any prior knowledge and/or meshing of matrix cracking surfaces, is accomplished by combining stress and fracture mechanics-based constitutive modeling within a mesh independent crack-modeling framework. Simulation results for a specimen with a [452/902/-452/02]s stacking sequence were compared with load-displacement curves and 3D X-ray micro computed tomography results from tested specimens. Excellent correlation was shown between the simulated and experimental load-displacement curves including proper representation of both the curve non-linearity and peak load. Similarly, remarkable correlation between simulated and experimental damage extent was shown. Delamination extent and shape were quite close. Crack distribution and extent was close but differed between the two data sets more than the comparison of delamination damage.
Polymer Degradation and Stability, 2011
While a great variety of high temperature polyimide materials exist, these materials are being su... more While a great variety of high temperature polyimide materials exist, these materials are being subjected to higher and higher use temperatures in oxidative and environmentally aggressive environments. There is a limit to the extent one can take a polyimide before it will oxidize and subsequently suffer property degradation, thermal decomposition, and structural failure. Therefore, we instead sought to use materials which do not oxidize (inorganic materials) to enhance the polyimide composition and perhaps move the properties of the organic polymer more into the realm of ceramics while maintaining polyimide composite weights and processing advantages. In this paper we present results of the combination of inorganic micron sized particles with and without carbon nanofibers to produce a variety of highly inorganic particle filled polyimides. These polyimides were tested for thermal stability and flammability in resin pellet form and as a protective coating for a carbonefiber composite structure. Our results demonstrate that the resin with inorganic particles exhibited significant reductions in flammability by themselves, but minimal flammability reduction when used as a thin coating to protect a carbonefiber composite. Further, the gains in thermal stability are limited by the thermal stability of the polyimide matrix, suggesting that more work is needed in measuring the limits of inorganic fillers to improve thermal stability. Still, the results are promising and may yield polyimide systems useful for providing resistance to damage from high heat flux exposures/fire risk scenarios.
Polymer, 2004
The structures of membranes of PBZO and PBZT extruded with counter rotating dies (CRD) were studi... more The structures of membranes of PBZO and PBZT extruded with counter rotating dies (CRD) were studied by wide angle X-ray diffraction (WAXD), small angle X-ray scattering (SAXS), atomic force, scanning electron and transmission electron microscopy (AFM, SEM, and TEM). The structure of CRD-extruded PBZO was compared with that of a solution-cast membrane. The extruded membranes have sheet structures typical of rigid-rod polymers. The heterocyclic rings of the extruded membranes are oriented approximately parallel to the membrane surface, while those of the cast membrane are oriented perpendicular to the surface. The parallel orientation of the rings of the extruded membranes may be due to the normal force exerted during extrusion. The polymer molecules near the surfaces of the extruded membranes are oriented along the shear directions of the extruder, while those in the middle are oriented randomly. There is little cholesteric nature. These materials have potential as microporous PEMs holding ion conducting polymers (ICPs).
Composites Part A: Applied Science and Manufacturing, 2012
Abstract Damage progression in laminated Overheight Compact Tension specimens was modeled using d... more Abstract Damage progression in laminated Overheight Compact Tension specimens was modeled using discrete representations of individual cracks and delaminations. Matrix cracking and delamination initiation, propagation, and interaction, without any prior ...
Macromolecular Chemistry and Physics, 2005
Silk fibers from the cocoon of Bombyx mori and the dragline of Nephila clavipes have been investi... more Silk fibers from the cocoon of Bombyx mori and the dragline of Nephila clavipes have been investigated by small angle x-ray scattering (SAXS) and atomic force microscopy (AFM). The large scale morphology of these silks have minimum scattering dimensions, and correlation length on the order of 150-300 nm. Several types of AFM measurements on peeled and abraided silk samples have
We have previously observed the dragline silk of Nephila clavipes and the silk of Bombyx mori exh... more We have previously observed the dragline silk of Nephila clavipes and the silk of Bombyx mori exhibit a range of morphological feature including microfibers (S. Putthanarat; R.K. Eby; W.W. Adams; G.F. Liu J.M.S.-Pure Appl. Chem. 1996, A33(7), 899) and a layered structure. In successive layers the microfibers appeared to be oriented at different small angles to the fiber axis. Further
The structures of extruded (counter-rotating die) polybenzobisoxazole (PBO) and polybenzobisthiaz... more The structures of extruded (counter-rotating die) polybenzobisoxazole (PBO) and polybenzobisthiazole (PBT) membranes wer examined with atomic force microscopy (AFM), scanning electron microscopy (SEM), and X-ray scattering. The results for PBO indicate that (i) nanofibrils are oriented parallel to the surface, (ii) the nanofibrils are oriented in opposite directions (±22º) on both surfaces due to the counter rotating die extrusion, (iii)
Submitted for the MAR06 Meeting of The American Physical Society Multi-scale Real-Space Character... more Submitted for the MAR06 Meeting of The American Physical Society Multi-scale Real-Space Characterization of Carbon Nanofiber Composites BENJI MARUYAMA, Air Force Research Laboratory, Materials & Manufacturing Directorate, SIRINA PUTTHANARAT, University of Dayton Research Institute, LAWRENCE DRUMMY, RICHARD VAIA, JONATHAN SPOWART, AFRL, Materials & Manufacturing Directorate, CARLA LEER, FERRIE VAN HATTUM, University of Minho, Portugal — Good dispersion of the reinforcement phase in nanocomposites is recognized as critical to achieving material property goals. Hierarchical nanocomposite morphologies can be quantified by a combination of 1) Reciprocal space methods such as scattering, 2) Real space imaging such as AFM and TEM, and/or 3) Inference from established structure-property models. However, none of these techniques alone has proven satisfactory to quantitatively characterize nanocomposite morphologies across multiple length scales and link them to properties. Nor have they been...
Aps Meeting Abstracts, Mar 1, 2002
The structures of extruded (counter-rotating die) polybenzobisoxazole (PBO) and polybenzobisthiaz... more The structures of extruded (counter-rotating die) polybenzobisoxazole (PBO) and polybenzobisthiazole (PBT) membranes wer examined with atomic force microscopy (AFM), scanning electron microscopy (SEM), and X-ray scattering. The results for PBO indicate that (i) nanofibrils are oriented parallel to the surface, (ii) the nanofibrils are oriented in opposite directions (±22º) on both surfaces due to the counter rotating die extrusion, (iii)
Polymer, Mar 1, 2004
Ultra-microindentation was used to measure the microhardness and modulus of silk (Bombyx mori) me... more Ultra-microindentation was used to measure the microhardness and modulus of silk (Bombyx mori) membranes, cast from 20 to 80 8C. The microhardness and modulus were determined from the loading/unloading curves. The membranes exhibit microhardness of about 400 MPa which is larger than the values for most common synthetic polymers (50-300 MPa) implying a greater scratch resistance. The moduli are of the order of those measured by the other means for B. mori silk membranes (5 GPa), and fibers (7-11 GPa). There is some correlation between microhardness and the dimensions of the grains/nanofibrils, but none with surface roughness. The results extend the range of an empirical correlation between microhardness and modulus. The present data together with previous data from other polymers fit the equation, H ¼ 0:55 E 0:74 ; with a correlation coefficient of 0.94. Finally, it is shown that elastic recovery of the silk membranes is an increasing function of the maximum load applied.
Polymer, 2000
Silk from 3-molted, 4-molted and sex-limited Bombyx mori, Antheraea pernyi and Antheraea yamamai ... more Silk from 3-molted, 4-molted and sex-limited Bombyx mori, Antheraea pernyi and Antheraea yamamai have been investigated using Atomic Force Microscopy and Low Voltage High Resolution Scanning Electron Microscopy. Nanofibrils, bundles of nanofibrils, helical features and a layered structure with a cross angle between nanofibrils in different layers were observed for all silks. Similar log-normal distributions of fibril widths were obtained from all silks with the geometric mean fibril widths covering the range of 90-170 nm. There is no correlation of the fibril width with the fiber size from different types of silkworm. Similar normal distributions of cross angles were observed in 30% of the images with the arithmetic means covering the range of 30-50Њ. There is an apparent correlation of cross angle with fiber size. The larger fibers for which the crystals are primarily alanine exhibit a greater average cross angle, 46Њ, than do those of the smaller fibers for which the crystals are primarily alanine and glycine, 36Њ. Initial wide angle X-ray diffraction measurements on a single fiber of A. pernyi are consistent with the fraction of fibrils at different cross angles being 28%. A simplified computer calculation method and molecular modeling were used in a search for packing angles which minimize the interaction energy of packing between beta sheets. Initial results revealed no definitive evidence of epitaxy to account for the cross angles. It is proposed that a multifibrillar fiber offers a number of mechanical advantages over a solid fiber with the same cross sectional area.
Journal of Macromolecular Science Pure and Applied Chemistry, Jul 1, 1996
ABSTRACT
Aps March Meeting Abstracts, Mar 1, 2005
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Papers by Sirina Putthanarat