Effect of fibre orientation on the low velocity impact response of thin Dyneema® composite laminates

Abstract

Ultra-high molecular weight polyethylene (UHMWPE) fibre reinforced composite materials are widely used in ballistic impact and collision scenarios due to their extremely high specific strength and stiffness. Exceptional levels of protection are provided by controlling the damage and deformation mechanisms over several length scales. In this study, the role of UHMWPE fibre architecture (cross-ply, quasi-isotropic and rotational "helicoidal" layups) is considered on the damage and deformation mechanisms arising from low velocity impacts with 150 J impact energy and clamped boundary conditions. Dyneema ® panels approximately 2.2 mm thick were impacted with a fully instrumented hemi-spherical impactor at velocities of 3.38 m/s. Full field deformation

A novel approach for the investigation of low energy ice impacts

“…In particular the displacement obtained by the drop tower was indirectly measured from Equation 4. As in [15], the DIC accuracy was also affected by the indirect capture of the target plate out of plane displacement due to the use of a mirror, which reflected and projected the superficial speckle pattern. The effect of the impact energy level was also considered in this preliminary study.…”

“…A schematic representation of the experimental set-up, similar to the one proposed by Hazzard et al in [15], is shown in Figure 1. The geometry of the low test area, i.e.…”

“…However, because of the spatial arrangement of the equipment, it was not possible to directly acquire images of the thin plate surface. Therefore, a mirror was placed under the test area with an angle of 45 • allowing to capture the reflected image, as shown in Figure 1 and proposed by Hazzard et al in [15]. In this way, the displacement field (Disp x , Disp y , Disp z ) and strain field (ε x , ε y , ε xy ) of the sample surface was acquired thanks to a superficial stochastic gray-scale speckle pattern.…”

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

“…The most commonly commercialised polyethylenereinforced composite panels (such as Dyneema ® HB25, HB26) consist of hotpressed layers of unidirectionally aligned fibers at 0°/90°. Even though this configuration enhances a good level of resistance to penetration, alternative orientations of the helmet layers leading to a quasi-isotropic behaviour provide a considerable decrease of BFD [239,241,243].…”

“…A possible reinforcement of this configuration (#P2) would be to consider each composite layer as a Dyneema HB26 stack. The latter, schematically represented in Fig.7.1 (right), is conformed by alternating plies of UHMWPE fibres oriented at 0°and 90°which are stacked by means of hot-pressing [243,250]. This cross-ply structure enables the assumption of a layer-level orthotropic behaviour [250].…”