# The High-Velocity Impact Behaviour of Kevlar Composite Laminates Filled with Cork Powder
They observed that cork cell walls experienced buckling, and in this context, the energy absorption at high strains can be quite considerable without signs of cell walls breakage. This suggest an almost complete recovery of their original shape and size. Moreover, the composite structures during its service life can be damaged due to impact loading, and this damage in composite material is of primary concern because it leads to large reduction in strength and compromises their structural integrity [30; 31]. [PERSON] et al. [32], for example, developed studies in composites incorporating cork powder, obtained from industrial by-products, and observed benefits in terms of impact strength and glass transition temperature (T\({}_{\text{g}}\)). When 2.5 wt.% was added to the polyester resin, the impact strength increased to around 18.5% and the T\({}_{\text{g}}\) to about 7.3% compared to the values obtained with the pristine resin. In another experimental study [33], these authors obtained benefits in terms of elastic recuperation and damaged area when cork powder was added to an epoxy resin, and higher penetration threshold and residual tensile strength of the laminates that incorporate the cork powder. For example, the elastic recuperation increased by about 26%, for a 21 J impact energy, and the damaged area decreased by around 15% for the same impact energy and compared to the values obtained for laminates with neat resin. Regarding the penetration threshold, these values were about 15% while the residual strength decreased around 47% for laminates subjected to an impact energy of 21 J [33]. In terms of fatigue properties, independently of the lower static bending strength (around 10% lower when 3 wt.% of cork powder was added to the resin), [PERSON] et al. [34] observed, based on a statistical analysis of fatigue data, that fatigue life is insensitive to the presence of cork into the resin. Finally, due to the viscoelastic properties of cork and polymeric matrices, [PERSON] et al. [35] performed a study where the stress relaxation and creep behaviour of multiphase composites incorporating cork powder were analysed in detail. For this purpose, composites with the same lay-up but with different fibres were produced. They concluded that higher values of relaxation and creep displacement occur when Kevlar fibres are used, but, independently of the fibres, higher values were also observed when cork powder was introduced into the resin. Therefore, based on the benefits achieved with this industrial by-product, the main goal of this work was to study the high-velocity impact behaviour of Kevlar composite laminates filled by cork powder, in order to obtain full knowledge of all loading modes. These fibres are of particular interest for military and civilian purposes, due to their high degree of toughness and good impact/ballistic performance. In fact, aramid fibres fail by a series of small fibril failures that absorb a significant amount of energy, resulting in very high toughness. For that purpose, this work focused on the ballistic behaviour and damage tolerance of Kevlar/epoxy reinforced composites, in which the epoxy matrix is filled with cork powder. The perforation velocity and energy absorption were estimated from experimental tests and damaged area was obtained by both C-scan ultrasound technique and visual inspection from impacted specimens. In order to evaluate the damage tolerance, bending after impact (BAI) tests were carried out.