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In the present study, ballistic resistance of sandwich composite structures for vehicle armor panel applications was investigated. The core material of the sandwich structure was a layer of Alumina ceramic and a layer of composite backing, sandwiched between 2D plain weave composite skins. The ballistic performance of sandwich materials with 3D backing was compared to the baseline 2D plain weave backed composites. An IMACON 200 high-speed camera was used to obtain high-speed photographs of the ballistic events of penetration and damage. These images were analyzed to study real time damage mechanism of the strike face surface of several targets and subsequently to obtain average resistive force of target points during impact. Velocities of projectile (armor piercing bullets) were recorded in all the experiments and were found to be in the range of 915 – 975 m/s. Post mortem analyses, which included sectioning of panel, were performed. Results showed that armor panels with 3D woven backing had a higher ballistic efficiency than the 2D baseline panels, strike face damage mechanics were predominantly axi-symmetric about the impact point and panels with 3D backing had controlled delamination and fewer complete penetrations.

The behavior of sandwich panels subjected to local loads and low-velocity impact is studied with analytical and numerical methods as well as quasi-static testing and low-sped impact testing. The results indicate that the core thickness has no influence on the initial part of the indentation behavior for a panel if the core thickness is larger than a certain critical core thickness. Both the analytical model and the numerical calculations agreed well with both the quasi-static testing and the low-velocity impact test.

Energy absorption of polymer and aluminum foam sandwich structures with glass-fibre composite skins was similar for 5-25J impacts. The polymer foam structure exhibited localized fibre fracture and core crushing as impact energy increased. The aluminum foam structure exhibited extensive plastic deformation, radiating from the impact point, at all impact energies.

A sandwich panel is described by an axisymmetric lumped mass/spring model. The panel compliance is simplified, considering only core shear deformation. Transverse penetrating impact is modeled; impactor diameter is significantly smaller than panel size. Experimental data for the total loss in impactor kinetic energy and momentum and estimated damage energy are given. For a selection of impactor tip shapes, the numerical model is used to evaluate different force-histories between the impactor and the panel during penetration

The behaviour of sandwich panels with different core structures after low velocity impact damage was investigated. The material properties are measured and the damage extensions are detected by ultra sonic testing. To assess the strength of the damaged sandwich structures, the panels are investigated in 4-point-bending tests until failure.

A rubber-filled multifunctional honeycomb sandwich composite was developed in this paper. This structure was composed of facesheets, honeycomb core and vulcanized liquid silicon rubber (LSR) in the honeycomb cells. The rubber fillings were designed to support honeycomb cell walls, act as viscoelastic dampers and dissipate impact energy functionally. In order to investigate the impact and damping performance of this new developed composite, low-velocity impact and vibration tests were conducted to the fabricated specimens in two groups, with and without rubber filled. Each group had three kinds of specimens with various stacked carbon/epoxy laminate facesheets, [0/90], [0/45/-45/90], [45/-45]. Damage areas of each impacted specimen were inspected by ultrasonic C-scan. For vibration tests, displacement response and damping ratio were checked and compared. The experimental results provided a good agreement with our material design concept.

Beyond the improvement of the structure stiffness, the stitches reinforce adhesion between the core and the skin and allows the structure to tolerate impacts of low energies. Even if we consider the increase of the mass of the panels which moderates the mechanical performances (specific properties), the interest of such reinforcements is considerable. The materials then created presents a real structural potential.

The patented Napcoê technology presented in this paper is designed to create in a continuous way 3D tailored sandwich structures while maintaining the production efficiency. The through-thickness reinforcement is obtained from regular fabrics. This process allows the production of complex preforms that can be post formed and impregnated with liquid resin using a closed molding production method or thermoformed in the case of thermoplastic composites.

A new concept of thermoplastic sandwich structures is presented. It relies on a fibre-reinforced core based on glass/thermoplastic commingled yarn and neat thermoplastic skins. Such a structure has been developed so as to manufacture a new range of storage tanks. The use of composites in the tank core structure results in a significant reduction of the total wall thickness, at identical industrial performances with the neat thermoplastic solution.

In order to benefit from the processing advantages of soft foam, as well as the high mechanical properties of rigid foam, a new type of polyurethane foam StructUre™ has been developed. It can, after fast and easy processing in its flexible state, be further cross-linked to a rigid state by means of high energy electrons. This results in a high-level mechanical property profile, making the originally soft foam suitable for application as rigid sandwich core material.