Dynamic behaviour of UHMWPE yarns and addressing impedance mismatch effects of specimen clamps

• Published in: International journal of impact engineering Vol. 37; no. 3; pp. 324 - 332
• Main Authors: Koh, A.C.P., Shim, V.P.W., Tan, V.B.C.
• Format: Journal Article
• Language: English
• Published: Kidlington Elsevier Ltd 01.03.2010; Elsevier
• Subjects: Constitutive model; Dynamic testing; Exact sciences and technology; Fracture mechanics (crack, fatigue, damage...); Fundamental areas of phenomenology (including applications); Physics; Solid mechanics; Static elasticity (thermoelasticity...); Strain rate; Structural and continuum mechanics; Vibration, mechanical wave, dynamic stability (aeroelasticity, vibration control...); Viscoelastic; Yarns; Constitutive model; Dynamic testing; Yarns; Viscoelastic; Strain rate; Constitutive equation; Ultra high molecular weight ethylene polymer; Viscoelasticity; Polyethylene; Stress wave; Stress strain relation; Modeling; Dynamic test; Finite element method; Strain wave; Hopkinson bar; Impact test
• ISSN: 0734-743X; 1879-3509
• DOI: 10.1016/j.ijimpeng.2009.10.008

The dynamic stress–strain behaviour of Spectra ® 900 yarns, made of highly oriented ultra-high molecular weight polyethylene (UHMWPE), is determined by means of a tensile split Hopkinson bar arrangement incorporating special grips to clamp the specimens. Test results show that a five-element viscoelastic constitutive model captures the behaviour of Spectra ® 900 yarns with good fidelity. Not uncommonly, as in this instance, grips used to clamp specimens introduce an impedance mismatch with the input/output bars, and the design of the clamps may not be amenable to modification to yield an impedance match. Consequently, an algorithm is developed to relate the strain signals from the input/output bars to what is experienced by the grips, and thus what is imposed on the specimen. This enables the extraction of corrected quantities for insertion into the Hopkinson bar equations. The proposed method is validated by finite element analysis.