-significantly different Poisson ratios between the fibre direction/perpendicular-to-the-fibre direction and the two perpendiculars to the fibre directions; -ply thicknesses between 30 and 70 μm.A constitutive anisotropic elasto-plastic law for this class of materials is proposed, and its validity with reference to Tensylon™ is verified experimentally. Satisfactory agreement is reached, and the viscous nature of the deviations between the model proposed and the experimental results is revealed.

Ultra-High Molecular Weight Polyethylene (UHMWPE) composites are the result of recent developments in material research for ballistic protection due to their ability to absorb the kinetic energy of the bullet by various mechanisms of dissipation, among which an important one is delamination. In order to study this mechanism independently, the laser induced shock wave testing procedure has been used on thin Tensylon� laminate samples. Laser-induced shock represents a modern approach that can be used for assessing the interlaminar bond strength between two plies of a composite material, in dynamic conditions, at high strain rates representative for a ballistic impact. Through this technique, a delamination failure stress threshold can be determined. In the present work, the laser induced shock technique was applied on the commercial UHMWPE material called Tensylon�. The delamination threshold of this material was determined by using the Novikov approach, and, compared to the literature, the results match the values determined by other means of measurement.

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Societal concerns on security push light weight armor for ballistic protection to remain a topic of interest. Ultra-High Molecular Weight Polyethylene composites (UHMWPE) have shown appreciable performances for ballistic protection, because of their ability to mitigate kinetic energy of projectiles by various mechanisms of dissipation and because of their lower density. Among dissipative mechanisms of interest, delamination is one of them. In order estimate the bond strength between two plies, the laser induced shock wave technique has been utilized on Tensylon® thin panels. Firstly, this paper introduces this technique and its capabilities with respect to the characterization of ballistic protections at very high strain rates (10 6 s À1 ). Secondly, a set of experimental results is shown and interpreted to obtain the interply bond strength, through the spallation process. At last, experimental results are supported by a numerical model that is in the verge of being a predictive tool.

Low velocity impact tests were conducted on quasi-isotropic [�45/0/90o]xs laminates under drop weight impact from 0.7m, corresponding to a 30J energy. In this respect modified epoxy blends reinforced with carbon and Kevlar woven fabrics laminates were developed using autoclave technology. The four configurations developed for low velocity impact tests aimed at investigating several aspects like: the effect of fiber type, stacking sequence and mainly technological processing parameters, on the impact performances. The recorded Load-Time curves were plotted and visual inspection, high resolution laser scanner were used to observe the fracture characteristics of the impacted composite laminates. The results obtained showed that for tested configurations, both stacking sequence and processing parameters directly linked to fiber volume fraction, have a strong effect on the impact performances. The amount of absorbed energy, ductility index was calculated for each configuration under study. The results obtained showed that hybrid configuration exhibits lower stiffness and damage initiation energy amount when compared to carbon reinforced configurations. Nevertheless, their damage propagation energy amount and ductility index was the uppermost. This behaviour was already reported previously [1] and is partially attributed to the higher elastic energy absorption of carbon fibers that delays the propagation of delamination, and fiber breakage. Lower tenacity obtained on hybrid laminates was attributed to both lack of resin local rinse saturate and to the intrinsic anisotropy of para-aramid fibers.