New Interference Approach for Ballistic Impact into Stacked Flexible Composite Body Armor

Phoenix, S. Leigh; Yavuz, A. Kadir; Porwal, Pankaj K.

doi:10.2514/1.45362

Cited by 21 publications

(10 citation statements)

References 5 publications

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“…Consequently, fibers underneath are simply in the way, in some respects acting as added mass to the fibers above, thus slowing down the transverse and tensile waves. Interference effects have been demonstrated experimentally by Cunniff [48] and theoretically by Porwal and Phoenix [45] and by Phoenix et al [46], to result in a substantial reduction in the critical failure velocity of multi-layer, hybrid systems. Much the same phenomenon can be expected in yarns.…”

Section: Strain Concentration From Impact and Shock Wave Distortion Omentioning

confidence: 95%

“…with respect to the pulley center, as is discussed in Porwal and Phoenix [45] and Phoenix et al [46]. (This velocity reflects the fact that the center of the pulley is moving at velocity c i with respect to ground, whereas the material is moving at velocityu (+) i with respect to ground, so the second must be subtracted from the first to obtain the relative speed at which material passes over the pulley.)…”

Section: Strain Immediately Following Impactmentioning

confidence: 99%

See 1 more Smart Citation

Modeling and Experiments on Ballistic Impact into UHMWPE Yarns Using Flat and Saddle-Nosed Projectiles

Phoenix

Heisserer

Werff

et al. 2017

Fibers

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Abstract:Yarn shooting experiments were conducted to determine the ballistically-relevant, Young's modulus and tensile strength of ultra-high molecular weight polyethylene (UHMWPE) fiber. Target specimens were Dyneema ® SK76 yarns (1760 dtex), twisted to 40 turns/m, and initially tensioned to stresses ranging from 29 to 2200 MPa. Yarns were impacted, transversely, by two types of cylindrical steel projectiles at velocities ranging from 150 to 555 m/s: (i) a reverse-fired, fragment simulating projectile (FSP) where the flat rear face impacted the yarn rather than the beveled nose; and (ii) a 'saddle-nosed projectile' having a specially contoured nose imparting circular curvature in the region of impact, but opposite curvature transversely to prevent yarn slippage off the nose. Experimental data consisted of sequential photographic images of the progress of the triangular transverse wave, as well as tensile wave speed measured using spaced, piezo-electric sensors. Yarn Young's modulus, calculated from the tensile wave-speed, varied from 133 GPa at minimal initial tension to 208 GPa at the highest initial tensions. However, varying projectile impact velocity, and thus, the strain jump on impact, had negligible effect on the modulus. Contrary to predictions from the classical Cole-Smith model for 1D yarn impact, the critical velocity for yarn failure differed significantly for the two projectile types, being 18% lower for the flat-faced, reversed FSP projectile compared to the saddle-nosed projectile, which converts to an apparent 25% difference in yarn strength. To explain this difference, a wave-propagation model was developed that incorporates tension wave collision under blunt impact by a flat-faced projectile, in contrast to outward wave propagation in the classical model. Agreement between experiment and model predictions was outstanding across a wide range of initial yarn tensions. However, plots of calculated failure stress versus yarn pre-tension stress resulted in apparent yarn strengths much lower than 3.4 GPa from quasi-static tension tests, although a plot of critical velocity versus initial tension did project to 3.4 GPa at zero velocity. This strength reduction (occurring also in aramid fibers) suggested that transverse fiber distortion and yarn compaction from a compressive shock wave under the projectile results in fiber-on-fiber interference in the emerging transverse wave front, causing a gradient in fiber tensile strains with depth, and strain concentration in fibers nearest the projectile face. A model was developed to illustrate the phenomenon.

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Section: Strain Concentration From Impact and Shock Wave Distortion Omentioning

confidence: 95%

Section: Strain Immediately Following Impactmentioning

confidence: 99%

Modeling and Experiments on Ballistic Impact into UHMWPE Yarns Using Flat and Saddle-Nosed Projectiles

Phoenix

Heisserer

Werff

et al. 2017

Fibers

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“…The interest in making simulations a more effective part of the design process has led to the recent development of a number of new fabric modeling approaches, including analytical [12], digital element [13], hybrid particle-element [14], hybrid finite element [15], multiscale finite element [16], and membrane finite element [17,18] methods. In general, analytical models adopt particular geometric, kinematic, constitutive, or other assumptions in order to meet the fast turnaround times and low computational costs demanded in many design applications.…”

Section: Introductionmentioning

confidence: 99%

Impact Dynamics Simulation for Multilayer Fabrics of Various Weaves

Shimek

Fahrenthold

2015

AIAA Journal

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The high strength, light weight, and flexibility of fabric protection systems makes them an effective impact mitigation solution in some important engineering applications. Examples include body armor, fan blade containment systems, and orbital debris shielding. Most soft armor protection systems employ a plain weave fabric, suitable for use in flat or slightly curved geometries. However, future fabric protection system designs may employ nonplain weaves to protect highly curved surfaces (such as personnel extremities) or to optimize the performance of protection systems composed of a nonhomogeneous fabric stack. In recent research, the authors developed an improved hybrid particle-element method to simulate the ballistic impact performance of fabric protection systems. The new formulation is the first to address the full range of modeling issues (including penalty-based contact-impact, excessive yarn bending stiffness, and mass or energy discard) that have limited the effectiveness of legacy finite element-based fabric modeling methods for over two decades. Validation simulations modeled three-dimensional perforation dynamics in multilayer fabric stacks, and showed good agreement with new ballistic experiments conducted at three different target-layer counts for two different projectile types and four different weaves. Nomenclature= second Euler parameter coefficient matrix g = generalized nonconservative torque, N · m g e = contact-impact torque, N · m g v = viscous torque, N · m H = semiaxis scaling matrix, m −2 H = transformed semiaxis scaling matrix, m −2 i = vector component i i = particle or element i i; j = particle combination i, j J = moment of inertia matrix, kg · m 2 m = particle mass, kg m p = projectile mass, kg N = number of connected neighbor particles n = number of particles n w = number of particles spanning a yarn P = pressure, Pa q d = generalized nonconservative force, J q p = generalized nonconservative force, J q U = generalized nonconservative force R = rotation matrix r o = element reference length, m s = element length, m s o = element length in the reference configuration, m T = kinetic coenergy, J t = fabric thickness, m U = internal energy, J u = internal energy per unit mass, J · kg −1 u s = step function V = potential energy, J= generic vector in the fixed framê v = generic vector in the corotating frame w = yarn width, m Y = yield stress, Pa Y o = reference yield stress, Pa α = particle semiaxis scaling factor β t = transition particle stretch factor Γ d = damage strain energy release rate, J Γ p = plastic strain energy release rate, J γ = first Euler angle δ ij = Kronecker delta ϵ = total strain ϵ p f = plastic failure strain ϵ e = elastic strain ϵ p = plastic strain ζ = ellipsoidal coordinate ζ R = reference ellipsoidal coordinate η = heat transfer coefficient, J · s −1 · K −1 η p = thermal softening coefficient, K −1 θ = third Euler angle (without superscript) θ = temperature (with superscript), K θ m = melt temperature, K θ o = reference temperature, K θ H = homologous temperat...

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“…Hence, although such models represented a significant advance in the knowledge of this complex problem, they had little predictive capacity and were not useful for armour design. In the last few years, Phoenix and co-workers 16,17 have developed a new analytical model following a different approach. It assumes that the target behaviour can be approximated by a two-dimensional (2D) membrane and its deformation by a conical shape, with the conical wave velocity being a function of yarn strain.…”

Section: Introductionmentioning

confidence: 99%

Analytical simulation of high-speed impact onto composite materials targets

Paradela

Sánchez‐Gálvez

2013

The Journal of Strain Analysis for Engineering Design

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This article presents a relatively simple analytical model aimed at simulating high-speed penetration into composite materials targets. The model is based on a set of basic hypotheses common to other previous analytical models developed in our department and elsewhere. However, this new model is of a more refined nature acquisition that allows for reliable results without requiring the use of parametric data needed in previous models. For the first time, the model provides a qualitative explanation of the sudden drop of energy absorbed by the target with impact velocities slightly higher than the ballistic limit. A qualitative explanation, experimentally observed, of the shape of woven fabric laminates after impact is also noted. The model predictions of both ballistic limit and residual velocity after perforation reasonably agree with experimental results, in spite of the use of static data of the target material. Thus, this model may serve as a useful tool for a primary stage of composite armour design, permitting a large number of parameters to be screened before using higher cost numerical and experimental approaches.

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New Interference Approach for Ballistic Impact into Stacked Flexible Composite Body Armor

Cited by 21 publications

References 5 publications

Modeling and Experiments on Ballistic Impact into UHMWPE Yarns Using Flat and Saddle-Nosed Projectiles

Modeling and Experiments on Ballistic Impact into UHMWPE Yarns Using Flat and Saddle-Nosed Projectiles

Impact Dynamics Simulation for Multilayer Fabrics of Various Weaves

Analytical simulation of high-speed impact onto composite materials targets

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