Understanding the Thickness Effect on the Tensile Strength Property of Dyneema(®)HB26 Laminates

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.