Dynamic response of closed cell PVC foams subjected to underwater shock loading

摘要

A dynamic loading facility is developed to investigate the underwater shock response of poly vinyl chloride foams of varying densities. The shock loading facility consists of a water filled hollow cylindrical structure, with one end fully closed and the other end fitted with a nylon piston. A rigid striker is used to impact the piston, which creates an underwater shockwave. The facility is comprised of four separate sections, where the middle section is an optically clear acrylic window, and the other three sections are aluminum. The optically clear acrylic window is utilized for the employment of three-dimensional Digital Image Correlation in conjunction with high-speed photography (90,000-100,000 frames per second) to obtain full-field deformation data of the foams during shock loading. Pressure data is recorded using piezoelectric pressure sensors at different locations along the underwater shock tube. Peak pressures in the range of 1-10 MPa with exponential decays are generated by changing the striker velocity. Furthermore, quasi-static hydrostatic response of pre shocked foams is evaluated using a previously developed underwater loading facility. Strain rate of 10(3) s(-1) is obtained in foam specimens during the experiments. Findings showed substantial delay between the underwater shock loading and material response. Polyvinyl chloride foams recovered 80-90% of their original shape after underwater shock loading and also retained much of their energy absorption capacity.