An apparatus for tensile testing of engineering materials

We develop a novel apparatus and a n associated test protocol to measure the tensile response of materials. The apparatus allows testing of ring - shaped specimens , fibre yarns and tapes of arbitrary length ; it can be employed to conduct experiments at different strain rates and in different environmental conditions . The technique is tested at low rates of strain on several materials, including carbon fibres, metals, polymers and ceramics ; the tensile respon ses measured with the new apparatus are compared to those obtained from conventional measurements and found to be in good agreement with these

Numerical sensitivity studies of a UHMWPE composite for ballistic protection

Ultra-high molecular weight polyethylene (UHMWPE) has a high potential for ballistic armor applications due to the excellent weight specific strength inherent to this type of material. In this paper, a non-linear orthotropic material model for the UHMWPE, based on the product DYNEEMA® HB26, is used for assessing the influence of the material properties on the ballistic performance. The model, implemented in the commercial hydrocode ANSYS AUTODYN uses initially linear-orthotropic elasticity, subsequent non-linear strain hardening, multiple stress-based composite failure criteria and post-failure softening. The strength model is coupled with a polynomial equation of state. An experimentally supported material data set for UHMWPE, presented before, is used as a baseline for the numerical studies on high velocity impact. Parameter sensitivities are studied for these impact situations. The numerical predictions are compared to available experimental data over a wide range of impact velocities (1 km/s up to 6 km/s). The objective of this paper is to assess the influence of different material parameters on the predictive capability of high velocity impact simulations and subsequently provide guidelines for the required experimental characterization of UHMWPE under shock loading

A non-linear orthotropic hydrocode model for ultra-high molecular weight polyethylene in impact simulations

This paper presents detailed experimental characterization of quasi-static anisotropic directional strength properties as well as the shock behavior of ultra-high molecular weight polyethylene (UHMWPE) for the development of an advanced material model for this class of materials. Specifically, we consider Dyneema® HB26 - pressed from uni-directional (UD) tapes in a 0/90° stacking sequence. A material model based on a constitutive law with orthotropic, non-linear strength, shock response, composite failure and softening criteria is presented. A set of material parameters is derived for applications in hydrocodes (here: ANSYS AUTODYN). High- and hypervelocity impact tests with different impact velocities are used for preliminary validation and discussion of the predictive capabilities in view of future application