Abstract
In this study, an experimental and numerical investigation is presented on the effect of thickness and test rate within the pseudo static regime on the tensile properties of Dyneema®HB26 laminates. A detailed experimental presentation on the tensile testing of different thickness is presented and highlights the commonly seen observation that the tensile strength of a laminate reduces as a function of the specimen thickness. To understand these experimental observations, a constitutive material model of the individual macro fibril is developed and applied to modelling the fibre and upscaling to the laminate. The modelling strategy is implemented into ls-dyna and used to perform a parameter study on the specimen geometries used in the experimental study. The model assumes that the fibril strength is a function of the amorphous volume within the fibre and hence fibril. It can be observed that the experimental behaviour can be simulated by modelling the interface between laminate plies and the fibril, and hence fibre failure. The weak interfaces from the fibril to the laminate scale make the testing of fibres and laminates very difficult. Hence, it is proposed that the intrinsic fibril strength should be used as a measure of strength, and the fundamental strength is determined through numerical studies.
Highlights
High performance fibres made of gel-spun ultra-high molecular weight polyethylene (UHMwPE)
Dyneema® fibres are manufactured via the gel-spinning process (Figure 1)
Figure a series of snapshots takentaken duringduring the tensile on Dyneema
Summary
High performance fibres made of gel-spun ultra-high molecular weight polyethylene (UHMwPE)have been increasingly used in multiple applications, such as ballistic protection, since their first synthesis in the 1980s. High performance fibres made of gel-spun ultra-high molecular weight polyethylene (UHMwPE). Dyneema® fibres are manufactured via the gel-spinning process (Figure 1). A solution of polyethylene having very long polymeric chains is continuously extruded and the chains are partially aligned when forced through the spinneret. Modifications and improvements of the manufacturing process have been applied to the production of different grades of yarns, each with a unique combination of properties [2,3]. The molecules within these fibres have a typical length of 36 μm [4]
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