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Showing 1 to 18 of 18 for “"crazing"”.
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Characterization of Crazing Properties of Polycarbonate
… and determine if the total surface area of crazing is the sole factor in residual properties or if the crazing stress plays a role. To obtain these goals, a new in-situ reflective imaging technique was developed to quantify the craze severity in transparent polymers. To accomplish the goal …
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Crazing and large deformation behavior in a model set of polystyrene/polybutadiene diblock copolymers
Thesis (Sc.D.)--Massachusetts Institute of Technology, Dept. of Chemical Engineering, 1984.
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Micromechanics of toughening in polymeric composites
… is often limited due to either localized crazing followed by failure [e.g., polymethyl-methacrylate (PMMA), polystyrene (PS)], or cavitation-induced brittle failure under high triaxiality [e.g., polycarbonate (PC)]. Judicious choice of polymer composites alleviates the above concerns by …
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Effect of intermediate solvents on poly(ether ether ketone)
… unstressed specimens were explained in terms of crazing and SINC. Microtensile tests were performed on completely swollen PEEK specimens. Plasticization and delocalized crazing were found in the case of amorphous PEEK exposed to the three solvents and semi-crystalline PEEK exposed to methylene …
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Microporous polymeric membranes via melt processing
… transition temperature (T_g) of the minor phase. Crazing structure is initiated during the post-step treatments. The dimensions of the crazes are then enlarged by a series of stretching processes that comprise consecutive steps of cold stretching followed by hot stretching. Rates of craze …
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Phase field modeling of the defect evolution and failure
… to study the failure under shear yielding and crazing conditions. And if local defects in the samples such as voids are included explicitly in the simulations, the PFDM is able to explain the breakdown of the pressure modified von Mises relation during crazing, which is due to the local stress …
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A thermo-mechanical finite deformation theory of plasticity for amorphous polymers : application to micro-hot-embossing of poly(methyl methacrylate)
… states in which this material does not exhibit crazing. We have implemented our theory in the finite element program ABAQUS/Explicit. The numerical simulation capability of the theory is demonstrated with simulations of the micron-scale hot-embossing process for manufacture of microfluidic …
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An internal variable theory for isotropic visco-elastic-plastic solids : application to indentation of amorphous polymeric solids
… under which this material does not exhibit crazing, and we outline detailed procedures for material parameter determination from these experiments. We have implemented the three-dimensional constitutive equations in the finite-element computer program ABAQUS/Explicit (ABAQUS, Inc., 2002), …
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Mechanism of Fatigue Crack Growth at Polymer/metal Interface
… the damage in the polymer took the form of crazing and cavitation. In contrast, laminar shear occurred under high shear loading, resulting in a larger amount of plastic dissipation at the crack tip and improved fatigue crack growth resistance. Based on the understanding of the mixed-mode …
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An investigation of the failure mechanisms of thermoplastic composites at various rates of strain and temperatures
… such as matrix plastic deformation, matrix crazing and tearing, fibre-matrix debonding, fibre fracture, fibre orientation and crack propagation. These deformation behaviours are influenced by the test conditions such as strain rate, temperature and the type of the test conducted. The …
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Highly Tough, Stiff, and Transparent Poly(Methyl Methacrylate) Composites Incorporating Thermoplastic Elastomer Nanofibrils
… toughening mechanisms are identified as multiple crazing at slow deformation speeds and cavitation followed by subsequent ductile shear yield of the surrounding matrix at high deformation speeds. This thesis advances the fundamental understanding of the processing-structure-property relationships …
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Rate and time dependent behavior of structural adhesives
… is shown that a rate dependent stress-whitening (crazing) phenomenon occurs prior to the maximum stress. A region of elastic behavior, a rate and time dependent region, and a region of perfectly plastic flow are identified in the stress-strain behavior. Information regarding variations of …
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Two-dimensional clay and graphene nanosheets for polymer nanocomposites and energy storage applications
… for all epoxy-graphene systems. A microcrack-crazing mechanism was proposed to explain the fracture behavior of epoxy-graphene systems based on fractography observations. Similar peak behavior of fracture toughness was not observed in UP system. UP nanocomposites with modified graphene oxide …
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Correlation of physical and chemical properties of anhydride-cured epoxy resins with theoretical structure
… having the lowest property retentions due to crazing. Vinyl monomers were added to the unsaturated systems in an attempt to enhance properties by promotion of the reaction through unsaturation. These additions were found to produce no advantageous properties except viscosity reduction; an …
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The use of silicone resins as corrosion protective coatings for magnesium alloys
… Resin 803 was found to be unsatisfactory due to crazing. Cobalt naphthenate was shown to be a more efficient curing accelerator than benzoyl peroxide when used in a concentration of 0.30% based on the solid resin content. Benzoyl peroxide was proved to be better than no curing accelerator at all. …
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The role of molecular length scale on the viscoplastic response of amorphous polymer nanofibers in the glassy state
… where PS fails at small strains due to crazing. This dissertation research focused on direct experiments with atactic PS nanofibers to elucidate and quantify the unusual viscoplastic response of ultra-small volumes of PS as a function of the underlying molecular and structural length …
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Bonding of additives to functional polyolefins by reactive blending
… The polymeric samples demonstrated resistance to crazing when the NOR-HALS were bonded to the polymer. For both the colorant and UV stabiliser areas of research, thermal properties of the materials were assessed using differential scanning calorimetry (DSC). It was found that increasing the …
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Mechanics and multi-physics deformation behavior of polymer electrolyte membranes
… suggesting a driving force for cavitation or crazing. A study of the effect of ramp rate and hold time reveal a significant time dependence of the pressure, which is not surprising given the significant rate dependence observed for Nafion under uniaxial mechanical loading. Simulations of this …