Raufoss, Norway
Raufoss, Norway

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Daiyan H.,Sintef | Andreassen E.,Sintef | Grytten F.,Sintef | Lyngstad O.V.,Plastal AS | And 2 more authors.
Polymer Testing | Year: 2010

The low-velocity, low-energy impact response of a mineral and elastomer modified polypropylene was characterised by instrumented falling-weight impact testing of plates with annular clamping. Different loading conditions were assessed by varying plate thickness (2-4 mm), incident impact velocity/energy (up to 4.4 ms-1/34 J) and temperature (-60 to 20 °C). Force-deflection curves and fracture patterns were categorised and analysed. The main trends can be explained in terms of 1) deformations spanning from small-strain bending to large-strain stretching, 2) fracture responses spanning from linear-elastic brittle to highly ductile, 3) process-induced anisotropy, and 4) friction effects. With the highest impact velocity used in this study, plates thinner than ∼2.5 mm fractured at both-30 and 20 °C, although with different mechanisms. A remarkable finding was that the central radial crack under the striker ran parallel to the (injection moulding) flow direction for the most brittle fractures (at low temperatures), while it ran perpendicular to the flow direction in other cases. © 2010 Elsevier B.V. All rights reserved.


Daiyan H.,Sintef | Andreassen E.,Sintef | Grytten F.,Sintef | Lyngstad O.V.,Plastal AS | And 4 more authors.
Polymer Testing | Year: 2010

The low-velocity, low-energy impact response of a mineral and elastomer modified polypropylene was characterised by instrumented falling-weight impact testing of plates with annular clamping. Most of the impact tests were performed at -30 °C with incident impact velocities in the range 1.0-4.4 m/s, and with plate thicknesses in the range 2.0-3.9 mm. The following factors were investigated: moulding conditions (mould temperature, melt temperature, holding pressure), striker geometry, clamping, plate surface texture, melt flow weld lines and paint. The occurrence of brittle fracture was affected by all these factors, except the moulding conditions. Reducing the striker hemisphere diameter or changing to a flat striker induced brittle fracture. Removing the annular clamping led to a more brittle response. Plates with a weld line were more brittle than standard plates. The surface texture caused brittle fracture when the textured side was in tension under the striker. The paint induced brittle fracture at -30 °C, but no adverse effect of the paint was observed at 20 °C. © 2010 Elsevier Ltd. All rights reserved.


Daiyan H.,Sintef | Grytten F.,Sintef | Andreassen E.,Sintef | Osnes H.,University of Oslo | And 2 more authors.
Materials and Design | Year: 2012

Mechanical impact loading of injection-moulded components was simulated. The material was a talc-filled and elastomer-modified polypropylene used in automotive exterior parts. The material model was the linear-elastic-viscoplastic SAMP-1 model, which features pressure-dependent yield stress, plastic dilatation and a simple damage model. The model was calibrated with data from tests in uniaxial tension, shear and uniaxial compression, utilising 3D digital image correlation for full-field displacement measurements. With the calibrated model, two load cases were simulated; centrally loaded clamped plates and three-point bending of bars. The predictions of force vs. deflection were good to fair. The results are discussed in terms of deficiencies of the calibration data, heterogeneity and anisotropy of injection-moulded components, and shortcomings of the model. In particular, the hardening curves at high strain rates are uncertain, and tests in biaxial tension would be useful. © 2012 Elsevier Ltd.

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