Non-explosive simulated blast loading of balsa core sandwich composite beams

A dynamic loading method for simulating explosive blast was developed using a crushing foam projectile launched by a gas gun at velocities ranging from 30 to 60 m/s. The objective of this test method is to dynamically load “small-scale” composite beam specimens so as to allow for the dynamic failure characterization of these materials subject to blast-type loads. Such non-explosive test methods are desirable since they are more easily implemented, less expensive, and safer than actual explosive blast tests. Furthermore, instrumentation and visual documentation of the experiment is more easily achieved in the absence of “spatially extended” blast pressures, fireballs, and other destructive phenomena associated with the use of explosives that obscure observation. This paper focuses on the description of the pressure pulse generating projectile development and the dynamic pressure profiles produced. Control of the pressure pulse is achieved via selection of foam density used as a crushable media in the projectile, developing peak pressures ranging from 3 to 6.5 MPa. Application of this projectile onto beam specimens show dramatic rate dependency of the composite compressive failure strain (143% higher for strain rate of 101 s−1 relative to quasi-static), whereas the tensile failure strain showed less, yet still significant, increase (29% for 101 s−1 strain rate relative to quasi-static) for dynamic loading rates. Sandwich beams all failed in core shear for the configuration tested, with no significant rate dependency for the shear failure strain of the balsa core material.