Experimental and Numerical Study of Near-Field Explosion with Small Charges on Composite Structure

Abstract The main purpose of this publication is to study the pressure generated by a near-field explosive charge, for example placed close to an aircraft composite fuselage. Representing explosive charges in the near-field is a crucial problem when it comes to analyzing the vulnerability of a composite structure subjected to such a dynamic load. The air blast experimental tests revealed saturation of the sensors in the near-field area. Two conditions of pressure measurements are investigated, one for the classical indicator called reduced distance W equals to 0.81 m/kg 1/3 and another one in the far-field. For reasons of confidentiality, information on the mass of the explosive and its distance from the target is not given and is normalized using arbitrary quantities. This is the case for all values used to calculate the mass of the explosive and its distance from the target. The paper shows how to take advantage of a situation where the explosive charge does not completely disable the near-field sensors. It is about the development of an original approach, gathering experience and calculations to model a representative pressure-time history. Partial experimental measurements are extrapolated using Eulerian numerical simulations performed by French CEA DAM’s Ouranos hydrocode. The operational character of the extrapolation is demonstrated by comparing the results of the simulation with experimental data gathered by the far-field sensors. Finally, these pressures measured will be used to investigate the structural response of an aeronautical composite structure under the near-field blast. The experimental work involves accurate instrumentation of a representative composite structure (through the MITE concept), high-speed measurements using both digital image correlation and Doppler laser interferometry, and carefully positioned pressure sensors, including in the near-field zone where sensor damage is likely. The divergent 1D spherical blast computed using the Eulerian component of the Ouranos hydrocode is then mapped into a 3D blast wave used to load the composite structure. The structural response is modeled in Abaqus/Explicit with cohesive elements between composite plies, allowing for delamination. The results are qualitatively compared with experimental displacement measurements and post-mortem ultrasonic analyses and show promising agreement.