Kedar S. Pandya

Ballistic impact behavior of carbon nanotube and nanosilica dispersed resin and composites

Experimental studies are presented on the ballistic impact behavior of nanoparticle dispersed materials viz. symmetric balanced cross-ply laminates made using unidirectional E-glass fabric with epoxy resin and neat epoxy resin. The nanoparticles used are nanosilica and multi-walled carbon nanotube for polymer matrix composites and nanosilica for epoxy resin. For comparison, studies are carried out on symmetric balanced cross-ply E-glass/epoxy and neat epoxy resin without nanoparticles. Effect of nanoparticle dispersion on ballistic limit velocity, V50 and energy absorbed has been studied. It is observed that V50 can be enhanced up to 6.3% for polymer matrix composites and up to 7.3% for neat resin on addition of nanoparticles. Also, energy absorbed can be increased up to 13.0% for polymer matrix composites and up to 15.2% for neat resin on addition of nanoparticles. Damage and energy absorbing mechanisms for different types of materials studied is also presented. Further, it is observed that the damage size on the target around the point of impact decreases on addition of nanoparticles. Quantitative data are given for high velocity impact behavior of the five types of specimens studied.

Analytical and experimental studies on ballistic impact behavior of 2D woven fabric composites

A generalized analytical formulation is presented for the prediction of ballistic impact behavior of 2D woven fabric composite laminates impacted with a rigid cylindrical projectile. The formulation is valid for a wide range of laminate thicknesses. The formulation is based on stress wave propagation and energy balance between the projectile and the composite target. During the ballistic impact event, the energy lost by the projectile is absorbed by the target through various damage and energy absorbing mechanisms such as compression of the target directly below the projectile, compression in the region surrounding the impacted zone, shear plugging, stretching and tensile failure of yarns/layers in the region consisting of primary yarns, tensile deformation of yarns/layers in the region consisting of secondary yarns, conical deformation on the back face of the target, delamination, matrix cracking, and friction between the projectile and the target. The formulation presented considers both shear plugging and tensile failure during conical deformation. Solution procedure for the evaluation of ballistic impact performance is presented. Experimental validation is performed on the ballistic impact behavior of two types of composite specimens: 2D plain weave E-glass/epoxy and 2D 8H satin weave T300 carbon/epoxy. Typical results on ballistic limit velocity and energy absorbed by various mechanisms are presented.

High-strain rate compressive behavior of multi-walled carbon nanotube dispersed thermoset epoxy resin

Compressive high-strain rate behavior of thermoset epoxy resin dispersed with multi-walled carbon nanotubes is presented. The present study investigates the effect of strain rate as well as effect of multi-walled carbon nanotube dispersion on the compressive stress–compressive strain behavior of thermoset epoxy resin. The amount of multi-walled carbon nanotubes dispersion was varied up to 3% by weight. The studies were carried out on compressive split Hopkinson pressure bar apparatus in the strain rate range of 800–3700/s. Processing of multi-walled carbon nanotubes-dispersed thermoset epoxy resin, testing, damage, and energy absorbing mechanisms and key findings are reported. It is observed that the compressive strength of thermoset epoxy resin increases up to 147% at high-strain rate compared with that at quasi-static loading. The corresponding increase for multi-walled carbon nanotubes-dispersed thermoset epoxy resin is up to 140%. It is also observed that the compressive strength and energy-absorption capability of thermoset epoxy resin increase with the addition of multi-walled carbon nanotubes.

Ballistic damage in hybrid composite laminates

Ballistic damage of hybrid woven-fabric composites made of plain-weave E-glass- fabric/epoxy and 8H satin-weave T300 carbon-fabric/epoxy is studied using a combination of experimental tests, microstructural studies and finite-element (FE) analysis. Ballistic tests were conducted with a single-stage gas gun. Fibre damage and delamination were observed to be dominating failure modes. A ply-level FE model was developed, with a fabric-reinforced ply modelled as a homogeneous orthotropic material with capacity to sustain progressive stiffness degradation due to fibre/matrix cracking, fibre breaking and plastic deformation under shear loading. Simulated damage patterns on the front and back faces of fabric-reinforced composite plates provided an insight into their damage mechanisms under ballistic loading.