Development of a scaled vehicle underbelly blast test method

Over the last three years TNO has explored the possibilities of fiber-reinforced composites to provide vehicle underbelly protection against blast loading. This work consists of three parts: • Numerical analysis of full-scale blast loading conditions in comparison to scaled blast loading conditions. • The development of a test method suitable to easily perform multiple test series supporting the development of optimal fiber-reinforced material composition; • The actual development of a fiber-reinforced material for blast protection. The first item has already been presented in an earlier MABS conference. Here, the development progress of the test method is further discussed. Full-scale experiments are performed by Defence / TNO by using the so-called NL reaction frame. With this setup, the response of flat-panel materials to typical underbelly STANAG 4569 blast loading conditions can be evaluated. The material response is captured by two high-speed cameras inside the reaction frame, and their stereo images can be used to determine the out-of-plane deformation field and in-plane material strains during the deformation process. However, significant effort is required to undertake these full-scale tests, which has led to the search for a more efficient way to evaluate the performance of composite materials against blast loading. A faster approach is found in quarter-scaled tests. By downscaling, multiple tests can be performed on a single day, allowing for faster evaluation of many material parameters, using limited specimen size (length, width and thickness) fiber-reinforced composite material samples. Downscaling requires comparison between full-scale and scaled tests to validate the scaling rules. This paper describes the comparison of full-scale and scaled STANAG 4569 level 2 steel pot tests on ARMOX 440. The test method used for composite material development is derived from the scaled STANAG (steel pot) configuration, but simpler and conservative relative to this standard method. This paper shows that the developed scaled test method is well suited for comparing different material options, up to the limits of the material performance, denting, partial failure and complete panel puncture.