Finite element modelling of Dyneema® composites: From quasi-static rates to ballistic impact

Abstract

A finite element methodology to predict the behaviour of Dyneema® HB26 fibre composites at quasistatic rates of deformation, under low velocity drop weight impact, and high velocity ballistic impact has been developed. A homogenised sub-laminate approach separated by cohesive tied contacts was employed. The modelling approach uses readily available material models within LS-DYNA, and is validated against experimental observations in literature. Plane-strain beam models provide accurate mechanisms of deformation, largely controlled through Mode II cohesive interface properties and kink band formation. Low velocity drop weight impact models of HB26 give force-deflection within 10% of new experimental observations, with in-plane shear strain contour plots from models directly compared with experimental Digital Image Correlation (DIC). Ballistic impact models utilising rate effects and damage showed similar modes of deformation and failure to that observed in literature, and provide a good approximation for ballistic limit under 600 m/s impact speed.

Experimental and Numerical Study on the Behavior of Dyneema� HB26 Composite in Compression

“…For moderate deformation values in the static out-of-plane compression tests the specific mechanical behavior of Dyneema® HB26 proved to be non linear even if the deformation is still mainly of elastic nature [10,11,27,32].…”

“…The numerical modeling of UHMWPE composites mechanical behavior when subjected to di-fferent loads was also intensively studied. Models based on the properties of cross-ply composite have been proposed on several papers [26][27][28][29][30]. Matrix properties influence on ballistic performance was also investigated by Hazzard, M.K., [27].…”

Assessment of head injury risk caused by impact using finite element models

“…In Lässig et al [250] this same material accounts additionally for an U s −U p equation of state (EOS), but it has not been implemented in the model of this study as the impact velocities remain in the ballistic regime and do not achieve hypervelocity conditions. This assumption was validated in the numerical study by Hazzard et al (2018) [254]. Therefore, the contribution of the equation of state would be negligible [250].…”

“…The material constants for the material description have been taken from Nguyen et al [253] and are summarised in Table 7.4. Additionally, nine plasticity constants are implemented to the model in order to define the anisotropic yield surface, whose expression is the following [242]: On the other hand, delamination is modeled as a surface-cohesive interaction where surface debonding is controlled by means of a mixed mode criterion involving failure modes I and II [254]. The parameters defining delamination are the Mode I normal strength (1.2 MPa) and fracture energy (0.544 Nmm −1 ) and Mode II shear strength (1.8 MPa) and fracture energy (1.088 Nmm −1 ).…”

“…The parameters defining delamination are the Mode I normal strength (1.2 MPa) and fracture energy (0.544 Nmm −1 ) and Mode II shear strength (1.8 MPa) and fracture energy (1.088 Nmm −1 ). These constants were experimentally obtained from quasi-static tests in the literature and posteriorly Hazzard et al [254] adjusted the value of the Mode II shear strength to 2.6 MPa in order to achieve a better match with the experimental impact tests at ballistic velocities. This last value is therefore assumed for further simulations in this section.…”