Dushyanth Sirivolu

Foam-Core, Curved Composite Sandwich Panels under Blast

An elastic-plastic model was developed for predicting the blast response of a foam-core, curved composite sandwich panel. A multi-layered approach was used to distinguish facesheets and core deformations. Core compressibility and transverse shear through the thickness were accounted for using linear displacement fields through the thickness. The predicted solution from the elastic-plastic model was shown to compare well with FEA from ABAQUS Implicit. A parametric study showed that blast resistance of the sandwich shell is increased by allowing cores to undergo plastic crushing. Very thick and shallow shells derive much of their resistance to blast from core crushing. Strong, dense foam cores did not increase the blast resistance of the curved sandwich panel but allowed facesheets to fracture while the core remained elastic.

Modeling Blast and High-Velocity Impact of Composite Sandwich Panels

Analytical models for predicting the deformation and failure of composite sandwich panels subjected to blast and projectile impact loading are presented in this paper. The analytical predictions of the transient deformations and damage initiation in the composite sandwich panels were compared with finite element solutions using ABAQUS Explicit. For the blast model, the predicted transient deformation of the sandwich panel was within 7%of FEA results, while the predicted damage initiation using Hashins composite failure criteria was about 15%higher than FEA results in most cases. For the high velocity impact model, the predicted transient deformations were within 20%of FEA results.

High Velocity Impact of a Composite Sandwich Panel

This paper presents analytical solutions for the deformation response of a composite sandwich panel subjected to high velocity impact by a rigid blunt, cylindrical projectile. The solution is derived from a 2-degrees-of-freedom model for the sandwich panel involving local indentation, core crushing, and global bending/shear deformations. An example is given for a composite sandwich panel consisting of orthotropic E-glass vinyl ester facesheets and PVC H100 foam core and subjecting to the high velocity impact of a blunt cylindrical projectile. The analytical solution for the local indentation and global deflection under the projectile was found to be within 15% of finite element analysis results.

Blast Mitigation Effects of Foam-Core, Composite Sandwich Structures

Structural polymer foams have been used as core material in lightweight sandwich panels for quite some time. Traditional sandwich theory suggests that the primary function of the polymer core is to transmit shear to the thin facesheets, thereby rendering high bending stiffness and strength from a panel with a minimum weight penalty. Recent analysis of the underwater blast response of PVC foam composite sandwich panel, however, shows that in addition to the above, PVC foams have blast mitigation effects through energy absorption via plastic core crushing. Close examination of the core stresses involved during initial yield has revealed that three-dimensional core plasticity is encountered in water blasts, and plastic work dissipation of the core plays a greater role in blast mitigation. In air blast/air back cases, core yielding is primarily transverse shear, but in water blast/air back and water blast/water back cases, core yielding is due to combined transverse shear, transverse compression and/or hydrostatic pressure. Experiments have been conducted to obtain the hysteresis effects of PVC H100 subjected to combined transverse shear and compression. These have led to the development of a transversely isotropic, viscoelastic–plastic damage material model that can be adequately used to describe the behavior of foam operating in this environment.

Impact perforation of sandwich panels with Coremat

Analytical solutions for the quasi-static and low-velocity perforation of sandwich panels with woven roving E-glass/vinyl ester facesheets and Coremat were derived. A multi-stage perforation process involving delamination, debonding, core shear fracture and facesheet fracture was used to predict the quasi-static failure load and ballistic resistance of the panel. The high core-crushing resistance and damping of the Coremat resulted in rupture of the distal facesheet before the incident facesheet during panel perforation because they limited the amount of local indentation compared with global panel deformation. Analytical predictions of the quasi-static load-deflection response and the dynamic contact force history were within 10% of the test results.