Low Velocity Punch-Shear Response of Nanoclay and Graphite Platelet Reinforced Vinyl Ester Plates, Laminated Face Sheets and Sandwich Composites

Abstract

Focus of our research is on developing stronger, safer and more cost-effective structures for the new generation naval ships; especially nanoparticle reinforced glass/carbon polymeric based composites and structural foams for blast/shock/impact mitigation. Punch-shear test at low velocity impact is significant for mechanical characterization. Gama et al. [1] performed QS-PST experimental methodology to define elastic energy and absorbed energies of composites as a function of penetration displacement. This paper describes the punch-shear response of nanoparticle reinforced vinyl ester plates, laminated face sheets and sandwich composites using Dynatup 8250 drop-weight impact test system according to ASTM D3763 Standard [2]. Low-velocity tests were performed on 4″ × 4″ square plate specimens with fixed circular boundary condition and impacted by a hemispherical-head plunger with added mass. The impact load, displacement, energy plots and visual inspection of the post damaged specimens depicted the failure characteristics and punch shear response of these composites.

Surface Fractal Analysis for Estimating the Fracture Energy Absorption of Nanoparticle Reinforced Composites

“…VSM and SIM are used independently to determine the fractal dimension of conventional hot rolled steel and cast iron fractured under quasi-static axial tensile tests. Dimensionalities so obtained are compared with the trend of tortuosity evaluated using the concept explained in earlier studies [ 11 , 17 ]. A large difference is observed between the dimensionalities obtained from VSM and SIM.…”

“…Area under the experimental load-deflection response curve ( Figure 10 a) provides the total energy absorption corresponding to all failure mechanisms ( Figure 10 b) under quasi-static tensile loading. It is to be noted that all experimental data has been normalized to the respective specimen areal density-NTAD [ 17 , 18 ].…”

“…, damage initiation phase and damage propagation phase. The load-deflection response ( Figure 13 b) from low velocity punch-shear tests on the same set of nanocomposites was studied in a previous investigation [ 17 ]. The amount of energy absorbed during each phase is the area under the corresponding portion of the load-deflection curve.…”

“… ( a ) Damage initiation and puncture propagation phase on a typical load-deflection response of nanocomposites under low velocity punch-shear; and ( b ) Experimentally obtained load (NTAD)-deflection response [ 17 ]. …”

“…The exfoliation and homogeneous dispersion of the nanoplatelets in polymer matrix are performed using sonication technique [ 16 ]. Coupons of these four different nanocomposite configurations are tested in quasi-static axial tensile and low velocity punch-shear loading according to ASTM standards D638 and D3763 respectively, and the improvement of mechanical properties is compared with respect to the pristine Derakane 510A-40 brominated vinyl ester polymer samples [ 17 , 18 ]. Specimens that are tested under low velocity punch-shear loading along with the corresponding material properties are shown in Table 1 .…”