Universal mechanical response of polypropylene under cyclic deformation
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Abstract
Experimental data are reported on isotactic polypropylene in uniaxial tensile (i) cyclic tests (oscillations between maximum strain 0.15 and the zero minimum stress) with various cross-head speeds and (ii) relaxation tests at temperatures ranging from room temperature to 100°C. Observations in cyclic tests show that maximum stresses decrease, while minimum strains grow with the number of cycles. A universal character is revealed of the dependence of minimum strain on the number of cycles: this function is independent of temperature and weakly affected by strain rate. To rationalize this observation, constitutive equations are proposed in cyclic viscoelasticity and viscoplasticity of semicrystalline polymers and a scenario is suggested for damage accumulation. Two types of damage are distinguished which are induced by (i) lamellar fragmentation in the crystalline phase and (ii) nucleation and growth of micro-voids in the amorphous matrix. The stress–strain relations involve five adjustable parameters that are found by fitting observations (50 cycles of loading–retraction) at room temperature and α-transition point. Numerical simulation demonstrates that the model correctly describes experimental data and can predict observations in tests with a large number of cycles.
©2012 by Walter de Gruyter Berlin Boston
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Articles in the same Issue
- Original articles
- Unsaturated polyester-clay slurry nanocomposites
- Copolymerization of norbornene with styrene catalyzed by Ni{CF3C(O)CHC[N(naphthyl)]CH3}2/B(C6F5)3 and transparent films
- Effect of silica nanoparticle loading and surface modification on the kinetics of RAFT polymerization
- The integrated curved surface imprinting process technology aided by gas and gray-scale regulated electromagnetic force
- Universal mechanical response of polypropylene under cyclic deformation
- Micromechanical modeling and strength prediction of short fiber reinforced polymers
- Influence of the specimen thickness on low velocity impact behavior of composites
- Thermal degradation and physical aging of linear low density polyethylene and poly(l-lactic acid) blends
- Prelims
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