Sandwich-structured composite

About: Sandwich-structured composite is a research topic. Over the lifetime, 5853 publications have been published within this topic receiving 101126 citations.

A new rate-dependent unidirectional composite model - Application to panels subjected to underwater blast

Abstract: In this study, we developed a finite element fluid–structure interaction model to understand the deformation and failure mechanisms of both monolithic and sandwich composite panels. A new failure criterion that includes strain-rate effects was formulated and implemented to simulate different damage modes in unidirectional glass fiber/matrix composites. The laminate model uses Hashin’s fiber failure criterion and a modified Tsai–Wu matrix failure criterion. The composite moduli are degraded using five damage variables, which are updated in the post-failure regime by means of a linear softening law governed by an energy release criterion. A key feature in the formulation is the distinction between fiber rupture and pull-out by introducing a modified fracture toughness, which varies from a fiber tensile toughness to a matrix tensile toughness as a function of the ratio of longitudinal normal stress to effective shear stress. The delamination between laminas is modeled by a strain-rate sensitive cohesive law. In the case of sandwich panels, core compaction is modeled by a crushable foam plasticity model with volumetric hardening and strain-rate sensitivity. These constitutive descriptions were used to predict deformation histories, fiber/matrix damage patterns, and inter-lamina delamination, for both monolithic and sandwich composite panels subjected to underwater blast. The numerical predictions were compared with experimental observations. We demonstrate that the new rate dependent composite damage model captures the spatial distribution and magnitude of damage significantly more accurately than previously developed models.

Ballistic limit determination of aluminum honeycombs—Experimental study

Abstract: Honeycombs are widely used as core structures in sandwich panels as energy absorbers. In this paper the ballistic limit velocity, energy dissipation and damaged zone of metallic honeycombs at normal impact are studied experimentally and compared with analytical formulae. In experiments aluminum 5052-H39 honeycombs are impacted by rigid steel cylindrical projectiles with a blunt nose. The ballistic limit velocities calculated from Alavi Nia's formulae [A. Alavi Nia, Ph.D. Thesis, Tarbiat Modarres University, 2002] show good conformity with experimental values. The differences between predicted ballistic limits and experimental data are found to be less than 10%. Energy studies show that folding of cell walls and shearing of plug have the main role in energy dissipation. The energy needed for folding of cell walls is about 71–85% of the initial kinetic energy of projectile. This quantity for shearing of plug is about 13–28%. The shearing of plug portion in energy dissipation is proportional to the second power of panel thickness, so that 25% growth in panel thickness results in 56.2% increase in the shearing of plug portion. The damaged zone formed by the projectile is almost circular in shape and its diameter is equal to the projectile diameter on the impacted side of the panels, but on the rear side of the panel the damage is elliptical in shape and its diameter is about 1.5–3 times of the projectile diameter.