SBIR-STTR Award

Fabric based protection systems are critical to many kinds of safety systems. A challenge as designs are attempted is that details of failure are not well understood and are difficult to model. For projectiles, failure is dependent on many parameters ranging from the size and shape of the impact point to the velocity of impact, and the conditions of the fabric in terms of weave, support, pre-tensioning and environment. For the designer trying to reliably handle a threat, this uncertainty cannot be resolved without significant testing. We will use a multi-scale approach to develop techniques to improve the fidelity of ballistics models for fabrics. Adaptive modeling techniques permit the resolution of necessary detail in failure regions so that reliable predictions can be. Designers have a variety of fabrics to choose from, including yarn impregnation techniques such as a shear thickening fluid. This research effort emphasizes effects of weaves as well as attempts to characterize in more detail how the shear thickening fluid effects the individual yarns and relates to ballistic performance. The end result will be a tool that designers can use to make decisions in the early stages of design using fabrics for safety systems

Fabrics are a key component in safety systems ranging from body armor to seat belts and airbags. Estimating the failure under various loading conditions is mostly beyond the state-of-the-art, so we seek a method to give designers more confidence in studying failure limits. Modeling improvements will involve a multi-scale adaptive finite element system using advanced object oriented programming techniques. This permits a consistent modeling approach that transitions from macroscopic multi-layer fabrics to fibril level model of yarns. The adaptivity will be done dynamically based on changing conditions of impact from projectiles, blast or other sources. Testing and constitutive modeling of yarns will be a major part of this effort. The properties of the yarn are critical to failure and the behavior of yarns is complex, given that they are composed of bundles of twisted fibrils that result in unusual properties. Constitutive modeling at the yarn/fibril level is absent from the literature and is a major goal of this research. Using a series of published tests, we will show that the resulting tool is capable of analyzing failure over a wide range of conditions. The final tool will be at a production level to study fabric safety systems.

Keywords:
Fabrics, Failure, Yarn, Adaptivity, Simulation, Ballistics, Constitutive Modeling