Modeling of Viscoelastic Behavior of Ballistic Fabrics at Low and High Strain Rates

David, N. V.; Zheng, James; Gao, X.-L.

doi:10.1615/intjmultcompeng.v7.i4.50

“…Standard viscoelastic models or some variants of them are used to model tissue responses. The number of material constants needed in such a model depends on how many springs and dashpots are used (e.g., [35][36][37][38]). However, linear viscoelastic models are suitable only over a small strain regime and are not adequate to describe tissue responses under blast loading.…”

Section: Linear Viscoelastic Modelsmentioning

confidence: 99%

Ballistic Helmets: Their Design, Materials, and Performance Against Traumatic Brain Injury

Kulkarni

¹

,

Gao

²

,

David

³

et al. 2012

Volume 8: Mechanics of Solids, Structures and Fluids

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a b s t r a c tProtecting a soldier's head from injury is critical to function and survivability. Traditionally, combat helmets have been utilized to provide protection against shrapnel and ballistic threats, which have reduced head injuries and fatalities. However, home-made bombs or improvised explosive devices (IEDs) have been increasingly used in theatre of operations since the Iraq and Afghanistan conflicts. Traumatic brain injury (TBI), particularly blast-induced TBI, which is typically not accompanied by external body injuries, is becoming prevalent among injured soldiers. The responses of personal protective equipment, especially combat helmets, to blast events are relatively unknown. There is an urgent need to develop head protection systems with blast protection/mitigation capabilities in addition to ballistic protection. Modern military operations, ammunitions, and technology driven war tactics require a lightweight headgear that integrates protection mechanisms (against ballistics, blasts, heat, and noise), sensors, night vision devices, and laser range finders into a single system. The current article provides a comparative study on the design, materials, and ballistic and blast performance of the combat helmets used by the US Army based on a comprehensive and critical review of existing studies. Mechanisms of ballistic energy absorption, effects of helmet curvatures on ballistic performance, and performance measures of helmets are discussed. Properties of current helmet materials (including Kevlar Ò K29, K129 fibers and thermoset resins) and future candidate materials for helmets (such as nano-composites and thermoplastic polymers) are elaborated. Also, available experimental and computational studies on blast-induced TBI are examined, and constitutive models developed for brain tissues are reviewed. Finally, the effectiveness of current combat helmets against TBI is analyzed along with possible avenues for future research.

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“…For example, three-parameter generalized Maxwell (GM) and generalized Kelvin-Voigt (GKV) viscoelasticity models were utilized by David et al [10] to describe the constitutive behavior of a ballistic fabric made from paraaramid fibers, Twaron CT716 R . It was assumed there that both the primary and secondary bond scissions are involved in the deformation process of the para-aramid fibers, leading to a linear mechanical response up to failure.…”

Section: Modeling Of Para-aramid Fibersmentioning

confidence: 99%

“…The viscoelasticity models developed here evolve from a recent study of the authors [10], where a three-parameter rheological model called the generalized Maxwell (GM) model was found to be suitable for characterizing the viscoelastic response of Twaron R fabrics. In the current study, the Burgers four-parameter viscoelasticity model (e.g., [26]) is used, and a five-parameter rheological model and a para-rheological model are developed for predicting the stressstrain response of the NR coated fabric and for achieving a better parametric correspondence of the rheological elements to the molecular deformation mechanisms.…”

Section: Constitutive Modelingmentioning

confidence: 99%

“…The reason for using the Maxwell element here is the same as that provided in Section 5.1. The adoption of the GM element in this model is based on the finding that it can describe the stress-strain response of the Twaron R fabric well [10]. It can be shown that the stress-strain relation furnished by the five-parameter model illustrated in Fig.…”

Section: Five-parameter Modelmentioning

confidence: 99%

“…Note that the original parameters of the para-rheological model (i.e., K 1 , K 2 , σ λ and η 1 ) do not appear explicitly in Eq. (10). Instead, the constitutive equation contains a new set of three parameters, K eff , K ve and τ, each of which is a combination of two or more original parameters.…”

Section: Para-rheological Modelmentioning

confidence: 99%

See 2 more Smart Citations

Constitutive Behavior of a Twaron®/Natural Rubber Composite

David

¹

,

Gao

²

,

Zheng

³

2010

Mechanics of Advanced Materials and Structures

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The constitutive behavior of a Twaron CT709R fabric/natural rubber (Twaron R /NR) composite is studied using the fourparameter Burgers model (composed of a Maxwell element and a Kelvin-Voigt element in series), a proposed five-parameter model (consisting of a Maxwell element and a generalized Maxwell [GM] element in series), and a newly developed para-rheological model (comprising a GM element and a stress network element in parallel). The new model makes use of the affine network-based molecular theory of rubber elasticity. The uniaxial stress-strain relation of the Twaron R /NR composite is experimentally determined at two constant strain rates of 0.00001 s −1 and 0.01 s −1 . The values of the parameters involved in the three viscoelasticity models are extracted from the experimental data. It is found that both the Burgers model and the five-parameter model significantly under-predict the stresses for large strain values at both the strain rates. In contrast, the constitutive response at each strain rate predicted by the newly developed para-rheological model is seen to be in good agreement with the measured stress-strain curve over the entire strain range studied. It is shown that the new model also predicts the elastic moduli and ultimate stresses of the Twaron R /NR composite well.

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Ballistic helmets – Their design, materials, and performance against traumatic brain injury

Kulkarni

¹

,

Gao

²

,

Horner

³

et al. 2013

Composite Structures

View full text Add to dashboard Cite

a b s t r a c tProtecting a soldier's head from injury is critical to function and survivability. Traditionally, combat helmets have been utilized to provide protection against shrapnel and ballistic threats, which have reduced head injuries and fatalities. However, home-made bombs or improvised explosive devices (IEDs) have been increasingly used in theatre of operations since the Iraq and Afghanistan conflicts. Traumatic brain injury (TBI), particularly blast-induced TBI, which is typically not accompanied by external body injuries, is becoming prevalent among injured soldiers. The responses of personal protective equipment, especially combat helmets, to blast events are relatively unknown. There is an urgent need to develop head protection systems with blast protection/mitigation capabilities in addition to ballistic protection. Modern military operations, ammunitions, and technology driven war tactics require a lightweight headgear that integrates protection mechanisms (against ballistics, blasts, heat, and noise), sensors, night vision devices, and laser range finders into a single system. The current article provides a comparative study on the design, materials, and ballistic and blast performance of the combat helmets used by the US Army based on a comprehensive and critical review of existing studies. Mechanisms of ballistic energy absorption, effects of helmet curvatures on ballistic performance, and performance measures of helmets are discussed. Properties of current helmet materials (including Kevlar Ò K29, K129 fibers and thermoset resins) and future candidate materials for helmets (such as nano-composites and thermoplastic polymers) are elaborated. Also, available experimental and computational studies on blast-induced TBI are examined, and constitutive models developed for brain tissues are reviewed. Finally, the effectiveness of current combat helmets against TBI is analyzed along with possible avenues for future research.

show abstract

Modeling of Viscoelastic Behavior of Ballistic Fabrics at Low and High Strain Rates

Cited by 7 publications

References 17 publications

Ballistic Helmets: Their Design, Materials, and Performance Against Traumatic Brain Injury

Ballistic Helmets: Their Design, Materials, and Performance Against Traumatic Brain Injury

Constitutive Behavior of a Twaron®/Natural Rubber Composite

Ballistic helmets – Their design, materials, and performance against traumatic brain injury

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