We have developed a Fluid-Structure Interaction (FSI) experiment to investigate the behavior of solid and sandwich panels subjected to underwater blast. The set-up is a highly instrumented scaled model designed to characterize the underwater blast impulsive loading of structures, and to identify their failure by means of real time measurements of deflection profiles, deformation histories, and fracture. In the FSI setup (Figure 1), a water chamber made of a steel tube is incorporated into a gas gun apparatus. A scaled structure is fixed at one end of the steel tube and a water piston seals the other end. A flyer plate impacts the water piston and produces an exponentially-decaying pressure history in lieu of explosive detonation. The pressure induced by the flyer plate propagates and imposes an impulse to the structure (panel specimen), which response elicits bubble formation and water cavitations.

Figure 1: Fluid-Structure Interaction Experimental configuration (top) modeled with Abaqus/Explicit simulation showing the pressure wave travelling in the shock tube and subsequent panel deflection (bottom left) and lab implementation with laser illumination used in the shadow moiré high speed imaging technique (bottom right).

By exploiting minimum weight design, material fabrication, structural integrity, dynamic experimentation, and large-scale simulations, major improvements can be made in the design of structures which require absorption or reflection of blast energy.

Figure 2: Shadow Moiré and High-Speed Photography (top) and cross-sectional view of deformed A304SS sandwich panels with various core topologies (bottom).

After having conducted research on core topological optimization of sandwich panels (Figure 2), the group is now looking at the performance of monolithic panels made of novel high performance steels developed by the Olson group at Northwestern University. This study will help to understand the relationships between material constitutive behavior and global performance of structures subjected to impulsive loadings. Novel martensitic and austenitic steel alloys are compared to commercially available steels such as HSLA. This will guide material designers to set performance objectives (strength, ductility, and necking stability) to realize optimal protective systems.

Personnel 

• H.D. Espinosa (PI)
• Phuong Tran (Postdoc)
• Xiaoding Wei (Postdoc)
• Alban de Vaucorbeil (Graduate Student)

Collaborators 

• Prof. G. B. Olson (Northwestern University)
• Prof. J. W. Hutchinson (Harvard University)
• Prof. H. N. G. Wadley (University of Virginia)
• Prof. T. Belytschko (Northwestern University)

Publications 

• L.F. Mori, D.T. Queheillalt, H.N.G. Wadley and H.D. Espinosa, "Deformation and Failure Modes of I-Core Sandwich Structures Subjected to Underwater Impulsive Loads," Experimental Mechanics, Vol. 49, No. 2, p. 257-275, 2009.

• L.F. Mori, S. Lee, Z.Y. Xue, A. Vaziri, D.T. Queheillalt, K.P. Dharmasena, H.N.G. Wadley, J.W. Hutchinson and H.D. Espinosa, "Deformation and Fracture Modes of Sandwich Structures Subjected to Underwater Impulsive Loads," Journal of Mechanics of Materials and Structures, Vol. 2, No. 10, p. 1981-2006, 2007.

• H.D. Espinosa, S. Lee, and N. Moldovan. "A Novel Fluid Structure Interaction Experiment to Investigate Deformation of Structural Elements Subjected to Impulsive Loading." Experimental Mechanics, Vol. 46, No. 6, p. 805-824, 2006.

• S. Lee, F. Barthelat, J.W. Hutchinson, and H.D. Espinosa. "Dynamic failure of metallic pyramidal truss core materials - Experiments and modeling." International Journal of Plasticity, Vol. 22, No. 11, p. 2118-2145, 2006.

• S. Lee, F. Barthelat, N. Moldovan, H.D. Espinosa, and H.N.G. Wadley, "Deformation Rate Effects on Failure Modes of Open-Cell Al Foams and Textile Cellular Materials," International Journal of Solids and Structures, Vol. 43, No. 1, p. 53-73, 2006.