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No description available.

No description available.

No description available.

No description available.

No description available.

Epoxy-bonding a composite plate to tension face, is an effective technique for repair and retrofit of reinforced concrete beams. Experiments have indicated local failure of the concrete layer between the plate and longitudinal reinforcement in retrofitted beams. This mode of failure is caused by local stress concentrations at the plate end, as well as at the flexural cracks. A method has been presented for calculating shear and normal stress concentrations at the cut-off point of the plate. Stress concentrations predicted by this method have been compared to both finite element method and experimental results. The analytical models provide closed form solutions for calculating stresses at the plate ends and can easily be incorporated in design equations. The ultimate capacity of the reinforced concrete beams strengthened by composite plates bonded to the tension face, is controlled by either compression crushing of concrete, rupture of the plate, local failure of concrete at the plate end, or debonding of the plate. These failure modes have been considered in developing design guidelines for flexural strengthening of reinforced concrete beams using fiber composite plates. Bonding composite plates (fabrics) to the web of reinforced concrete beams can increase the shear and flexural capacity of the beam. An analytical model has been developed to calculate the stress distribution in the strengthened beam, and the shear force resisted by the composite plate before cracking and also after formation of flexural cracks. Parametric study has been performed to reveal the effect of important parameters such as fiber orientation, and plate thickness. The ultimate shear capacity of reinforced concrete beams is also increased by epoxy-bonding composite plates to the side faces of the beam. Truss analogy and compression field theory have been used to determine the effect of the composite plate on the crack inclination angle and the shear capacity of reinforced concrete beams at ultimate state. The effects of important parameters such as plate thickness and fiber orientation angle on the crack inclination angle and the shear capacity of the strengthened beam have been investigated through a parametric study.

A pultrusion process using staggered cylindrical pins in a molten polymer reservoir is one method of pre-compounding long glass fibre-reinforced thermoplastic materials. This material, if well impregnated with resin, will maintain much of its aspect ratio during subsequent moulding. The longer fiber length translates into improved mechanical properties versus conventional extrusion compounded material. This research studies the effect of a novel pin shape and configuration on the wetting of glass roving during thermoplastic pultrusion compounding. / Experimental pultrusion studies using polypropylene indicate that alternating concave (collecting) and convex (spreading) contoured pins promote superior resin impregnation compared to conventional cylindrically shaped pins. A mathematical model describes the necessary convex pin contour and was used to fabricate the convex pins employed in the research. Pins thus designed promote uniform filament spreading across the wide convex contour which in turn favours good resin impregnation.

The purpose of this research project has been to evaluate the feasibility of improving the impact properties of polypropylene (PP)/ethylene vinyl alcohol copolymer (EVOH) laminar blends by the incorporation of a rubber phase. The impact modifier was poly (ethylene-propylene) rubber (EPR). The study was conducted initially with a batch mixer, and then continued with an extruder. Furthermore, it was decided to evaluate the improvement in impact toughness of the blends upon addition of a polyethylene (PE) phase. / The batch mixing studies showed that it is possible to bring the impact properties of maleated PP (MAPP)-based blends to the range of those exhibited by MAPP, by incorporation of both EPR and PE. The sequence of addition of EPR and PE is very important. The products obtained exhibited good adhesion at the interface between the dispersed phase and the matrix. The presence of EPR and PE did not affect the final oxygen permeabilities of the blends. / The extrusion studies showed that the morphology of the blends, and therefore their final properties, depend on the method of compounding. Different MAPP resins were used as the major phase. The best impact properties were found in the case of addition of the EPR-PE phase in a twin screw extruder. The oxygen permeabilities were disappointing, and appeared to be only slightly influence by compositional or processing parameters. One possible explanation is that moisture might have contaminated the EVOH phase, inhibiting its effectiveness as an oxygen barrier.

Thermoforming is a generic term for the manufacturing of plastic components through a vacuum or a pressure forming process. The first and most critical phase in thermoforming is sheet heating. For a thick-gage plastic sheet, the combination of conduction and radiation energy, which conducts and transmits into the sheet interior, controls the heating cycle time. In order to predict the formability of a thick-gage sheet and improve production efficiency, we need to know the internal temperature of the plastic sheet during the heating phase in thermoforming. Unfortunately, the internal temperature of the sheet is impossible to measure directly. To overcome this problem, it is possible to use a soft-sensor technique, which uses the surface temperature of a plastic sheet that can be measured by infrared sensors to estimate the internal temperature of the sheet. / A soft sensor system was defined by using a finite difference equation. Experiments and simulations were performed to determine how well the soft sensor was able to predict the temperature distribution inside a plastic sheet. The sensitivities of some key parameters, e.g., material absorptivity, thermal diffusivity, view factor and oven air temperature, are analyzed and discussed.