The modes of shear yielding in edge-notched sheets of polycarbonate have been studied under slow tensile loading. Optical microscope techniques were used to characterize the flow lines through the thickness of the plastically deformed region. Three modes are observed, namely core yielding, hinge shear and intersecting shear. Core yielding consists of two families of shear flow lines contained in the centre region where the stress is highest. In the nearly plane strain condition, the dominating shear mode is hinge shear which is through-thickness yielding on inclined planes above and below the notch. Intersecting shear dominates in the nearly plane stress condition. In this case, yielding occurs through the entire thickness by slip along planes parallel to the width direction that make an angle with the plane of the sheet. It produces a necking effect in front of the notch. The thickness dependent transition from hinge shear to intersecting shear follows conditions suggested by Hahn and Rosenfield.
A new thermoplastic elastomer with improved impact and tensile properties was produced through melt blending of graphene oxide filled nitrile butadiene rubber (NBR-GO) and polyvinyl chloride (PVC) without the addition of plasticisers and thermal stabilisers. Nitrile butadiene rubber (NBR) compounds, with and without graphene oxide (GO) are prepared through latex compounding method and cured, prior to blending with PVC. The effect of NBR and NBR-GO loading on the process-ability and physico-mechanical properties of PVC blends were evaluated. The addition of NBR and NBR-GO improved tensile strength (TS), impact strength and swelling resistance of PVC. Addition of NBR also increased the stiffness of PVC due to higher elasticity of NBR as compared to PVC. Optimum impact strength, TS and swelling resistance was achieved with the addition of 10 wt. % NBR-GO. Good miscibility between NBR and PVC, and additional reinforcement by GO is responsible for enhancement of impact and TS. NBR-GO showed greater miscibility in PVC as compared to NBR as proven by morphological observation under scanning electron microscope. Morphological observation reveals that micro-cracks formation on PVC/30NBR surface which is responsible for low impact, tensile and swelling properties as compared to PVC/30NBR-GO composite.
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