Characterisation of the impact behaviour of polymer thermoplastics

Experimental characterization and computational simulations of the low-velocity impact behaviour of polypropylene

“…The stress and strain fields generated can be supposed to be homogeneous in the calibrated part of the sample, unless necking appears. For the present work, experimental tensile impact isostrain rate curves obtained from an experimental programme developed previously were used. In these investigations, injection‐grade isotactic polypropylene homopolymer (SM6100K, Montell) was used.…”

“…where ϵ ( t ) is the logarithmic strain and x ( t ) the displacement. Here a homogeneous deformation state along the test sample has been assumed following the assumptions of Aretxabaleta et al . This approximation has been considered valid up to the breaking point since occurrence of a significant necking phenomenon was not observed (Fig.…”

“…Also, it is desirable that these experimental curves are obtained at constant strain rate so that the constitutive dependence of the polymer with the deformation rate can be established. There are a number of experimental methods to evaluate the impact response of polymers: on the one hand, there are the traditional falling dart, Charpy, Izod and Gardner tests, which are only suitable for ranking polymers in terms of their impact performance since they impose inhomogeneous stress–strain fields and variable strain rates; on the other hand, there are the more recent split Hopkinson pressure bar (SHPB) and tensile impact tests, which have been used for high strain rate (10–10 3 s −1 ) testing. Although these novel methods are attractive for mechanical characterization, since the specimen is assumed to undergo homogeneous deformation, in both SHPB and tensile impact tests a constant strain rate cannot be achieved.…”

“…Although these novel methods are attractive for mechanical characterization, since the specimen is assumed to undergo homogeneous deformation, in both SHPB and tensile impact tests a constant strain rate cannot be achieved. To overcome this drawback, Aretxabaleta and co‐workers developed a novel characterization method which involves the construction of isostrain rate curves from a series of tensile impact curves obtained at different impactor velocities …”

“…In later investigations, they used this model to simulate the impact of an amorphous acrylonitrile–butadiene–styrene polymer and semicrystalline poly(butylene terephthalate) polymer. For the calibration of their nine‐parameter model, they used experimental data from uniaxial compression tests at low strain rates (10 −3 –10 −2 s −1 ) together with SHPB for high strain rates (nominal 10 s −1 ). Their simulations showed good agreement with experimental data up to the maximum load.…”