Dynamics of Shear Thickening Fluids in Composite Beam Structures

McGovern, James
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University of Delaware
The next generation of armored vehicles will have to face a host of ever more lethal weapons platforms designed specifically to defeat armor plating. As weapons technology advances, traditional steel armors are quickly becoming obsolete. New armor systems have shifted to the use of high strength composites and ceramics. Unfortunately, these ceramics are brittle, and can become damaged merely by driving. Damage can be mitigated with a compliant interlayer between the armor plate and vehicle frame. However, this will reduce the overall protection from ballistic threats. Shear Thickening Fluids (STFs) have been proposed as a novel interlayer material. STFs can be engineered to remain liquid-like and fluid during vehicle mobility. Once struck by a high energy, high shear rate projectile, the STF will nearly instantly transform into a rigid solid-like state, effectively binding the armor and frame together and improving performance. Computer modeling of the dynamics of the interlayer system under various velocity profiles has shown the systems are highly sensitive to both the deformation rate, as well as the shape of the deformation rate v deformation curve. In particular, sinusoidal rates such as those generated by a dynamic mechanical analyzer cause viscous forces to dominate, while those similar to ballistic impacts stress elastic forces. The computer results were compared to experimental data with mixed results. The models were found to predict some features, but overestimate others. Further experimentation will be required to eliminate any possible systematic error in the experimental results before the simulations can be confirmed or denied.