Detailed study on yield, damage and failure of polymers and composites - modelling mechanical behaviour

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This proposal addresses testing and analytical modelling of the behaviour of polymers and polymer composites that are used in the construction industry. It includes studies on short-term and long-term performance and failure. Long-term performance, which influences failure mode and time, is likely the most critical issue that needs to be addressed in order to safely use polymers as structural materials. In this proposed research, polyethylene (PE) and fibre reinforced polymer (FRP) composites will be studied. Behaviour and failure of PE can be characterized by time-dependent stress-strain response, slow crack growth, creep rupture or yield stresses; all of which are directly related to its environmental stress crack resistance (ESCR). Typical testing involves tensile creep or tensile stress-strain testing; however, in this work we plan to extend this to compression and shear testing. PE is often utilized in construction as a support for metal elements (e.g for bridge cables) and thus compression and shear behaviour are important. Tensile, compression and shear testing of same types of PE will provide unique database that can be used for rational modelling methodologies. Development of such modelling is also part of this proposal.Fibre reinforced polymer (FRP) composites are a promising option in construction industry where the problems with corrosion need to be addressed, lightness of the material is important, or the electromagnetic inertness is required. We propose to develop methodologies for predicting strength of FRP composites through mathematical modelling. FRP utilize thermoset polymer matrices (polyester, vinylesther), which protect and bond fibres (glass, carbon, aramid). The study will concentrate on determination of strength based on mathematical model for inclusions and interfaces in the polymer matrix. This proposal describes a three-year research program, complementary to the on-going research (funded by Imperial Oil) on creep and failure behaviour of PE studied at the (microstructural) molecular level. The proposed research project is part of a larger research program carried out at the University of Waterloo.