Dynamic explicit step and general contact capability are appropriate for this type of explosion. 

Introduction

Aluminum sandwich structures with integrated energy absorbers have gained significant attention in protective engineering due to their high strength-to-weight ratio, excellent energy absorption capabilities, and tunable response under dynamic loading. One critical scenario for which these structures are designed is air blast loading, commonly caused by explosions in air. This type of loading results in a rapid pressure rise followed by a decay, imparting significant impulsive forces to any exposed structure.

When such a blast wave interacts with a sandwich panel typically comprising two thin aluminum face sheets and a lightweight core (e.g., foam, honeycomb, or lattice) the response is governed by the material properties, core geometry, and the presence of inner energy absorbers. These absorbers are added to improve structural survivability by enhancing energy dissipation and delaying or mitigating failure mechanisms.

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Air Blast Load Characteristics

An air blast wave from an explosion propagates through the air and can be idealized (for structural analysis) using the Friedlander equation for the pressure-time profile:

P(t)=P_s​(1−t_d​t​) e−^bt/td

​Where:

• P(t): overpressure at time t

• P_s: peak overpressure

• t_d​t​: positive phase duration

• b: decay coefficient

The impulse delivered to the structure is the area under this pressure-time curve and is a key factor in determining structural damage.

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Aluminum Sandwich Structures Under Blast Load

1. Composition:

• Face Sheets: Typically thin aluminum alloy (e.g., 2024-T3, 6061-T6) providing bending stiffness.

• Core: Lightweight material like aluminum foam, honeycomb, or lattice, offering shear strength and initial energy dissipation.

2. Failure Modes:

Under blast loading, these panels can fail through:

• Face sheet yielding or fracture

• Core shear failure or crushing

• Delamination between the face and the core

• Global bending or deflection exceeding limits

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Inner Energy Absorbers

Function:

Energy absorbers (e.g., metallic foam inserts, crushable tubes, origami structures) are placed inside or behind the core to:

• Absorb blast energy via plastic deformation

• Reduce transmitted force to critical components (e.g., payload or personnel)

• Delay face sheet rupture and panel debonding

Types:

• Metallic foams (aluminum, steel)

• Tubular systems (crush tubes)

• Origami-based structures

• Layered or gradient cores with varying densities or materials

Design Considerations:

• Placement: Between core layers or behind the rear face sheet

• Crush characteristics: Plateau stress, densification strain

• Mass efficiency: Trade-off between added weight and energy absorption

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Dynamic Response and Modeling

To evaluate performance under blast loading:

• Numerical simulation using finite element analysis (FEA) with Abaqus software

• Constitutive models for foam and face sheets (e.g., Johnson-Cook, damage,…)

Aluminum sandwich structures with integrated energy absorbers offer a promising solution for blast mitigation. Their design must balance lightweight requirements with sufficient strength and energy dissipation. Advances in materials and multi-functional absorber designs continue to push the boundaries of blast protection.