Study of the impact sensitivity of aluminum-polytetrafluoroethylene layered compositions

Denisaev, A. A.; Shteĭnberg, A. S.; Берлин, А. А.

doi:10.1134/s001250160706005x

Cited by 10 publications

(5 citation statements)

References 2 publications

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“…Mixtures containing polytetrafluoroethylene (PTFE) and aluminum (Al) are known to be energetic under dynamic and/or thermal loading. [1][2][3][4][5][6] These materials generate a large quantity of heat during the reaction driven by bulk mechanical deformation as in thermites. 7 This paper considers the mechanical behavior of PTFE-Al-W composites where tungsten (W) was used to increase density 8 keeping the composition of PTFE-Al mixture close to the stoichiometric value.…”

Section: Introductionmentioning

confidence: 99%

Particle size effect on strength, failure, and shock behavior in polytetrafluoroethylene-Al-W granular composite materials

Herbold¹,

Nesterenko²,

Benson³

et al. 2008

Journal of Applied Physics

124

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The variation of metallic particle size and sample porosity significantly alters the dynamic mechanical properties of high density granular composites processed using a cold isostatically pressed mixture of polytetrafluoroethylene (PTFE), aluminum (Al) and tungsten (W) powders. Quasi-static and dynamic experiments are performed with identical constituent mass fractions with variations in the size of the W particles and pressing conditions. The relatively weak polymer matrix allows the strength and fracture modes of this material to be governed by the granular type behavior of agglomerated metal particles. A higher ultimate compressive strength was observed in relatively high porosity samples with small W particles compared to those with coarse W particles in all experiments. Mesoscale granular force chains comprised of the metallic particles explain 2 this unusual phenomenon as observed in a hydrocode simulation of a drop-weight test.Macrocracks forming below the critical failure strain for the matrix and unusual behavior due to a competition between densification and fracture in dynamic tests of porous samples were also observed. Shock loading of this granular composite resulted in higher fraction of total internal energy deposition in the soft PTFE matrix, specifically thermal energy, which can be tailored by the W particle size distribution.Porous PTFE-Al-W specimens containing coarse W particles (denoted "porous PTFE-Al-coarse W") were processed with a significantly reduced CIPing pressure (20 MPa) to investigate the behavior of materials with different porosity and different particle sizes of W powder. This resulted in a similar porosity to samples with fine W particles (compare the Porous PTFE-Al-fine W sample with the Porous PTFE-Al-coarse W sample

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Section: Introductionmentioning

confidence: 99%

Particle size effect on strength, failure, and shock behavior in polytetrafluoroethylene-Al-W granular composite materials

Herbold¹,

Nesterenko²,

Benson³

et al. 2008

Journal of Applied Physics

124

View full text Add to dashboard Cite

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“…Mixtures containing polytetrafluoroethylene (PTFE) and aluminum (Al) are known to be energetic under dynamic and/or thermal loading [1][2][3][4][5][6] . They are similar in composition to thermites 7 , a subgroup of the class of pyrotechnics, and are formulated to generate a large quantity of heat during the reaction driven by mechanical deformation in the bulk material.…”

mentioning

confidence: 99%

The influence of metallic particle size on the mechanical properties of polytetraflouroethylene-Al–W powder composites

Cai

Nesterenko

Vecchio

et al. 2008

Applied Physics Letters

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The dynamic mechanical properties of reactive materials (e.g., high density mixtures of polytetraflouroethylene (PTFE), aluminum (Al) and tungsten (W) powders) can be tailored by changing the morphology of the particles and porosity. Cold isostatically pressed PTFE-Al-W powder composites with fine metallic particles and a higher porosity exhibited higher ultimate compressive strength than less porous composites having equivalent mass ratios with coarse W particles. The mesoscale force chains between the fine metallic particles are responsible for this unusual phenomenon. We observed macrocracks below the critical failure strain for the matrix and a competition between densification and fracture in some porous samples in dynamic tests. 2Mixtures containing polytetrafluoroethylene (PTFE) and aluminum (Al) are known to be energetic under dynamic and/or thermal loading [1][2][3][4][5][6] . They are similar in composition to thermites 7 , a subgroup of the class of pyrotechnics, and are formulated to generate a large quantity of heat during the reaction driven by mechanical deformation in the bulk material. This paper describes the mechanical behavior of the PTFE-Al-W composites with varying W particle size and porosity. Varying cold isostatic pressing conditions introduces different porosities and component configurations within the samples. The quasi-static and dynamic ultimate compressive strength of the composites were measured to identify influence of their mesostructure on mechanical properties and fracture. The unusual phenomenon of increased strength of porous composites with reducing size of metallic particles was observed. A two-dimensional Eulerian hydrocode is used to numerically model the composite systems to explain experimental phenomenon.Tailoring the mechanical and chemical properties of reactive materials is important for various applications. For example, varying particle size and morphology in pressed explosives (HNS) 8 or layer thicknesses in laminate 9 can be used for tailoring of shocksensitivity and the rate of energy release. The stress/force chain formation in granular energetic materials can be related to ignition sites within composite energetic materials under a compressive load 10 . Bardenhagen, Brackbill 11 and Roessig, Foster, and Bardenhagen 12 examined the localized stress propagation due to force chains and effects of binder in two dimensional particle bed under static and dynamic loading.Cold Isostatic Pressing (CIPing) was used to prepare specimens from a mixture of 17.5 wt% PTFE, 5.5 wt% Al, and 77 wt% W powders with different porosities. The initial powders had the following average sizes: Al: 2 μm (Valimet H-2); coarse W powder: < 44 μm (Teledyne, -325 mesh) and fine W powder with particle sizes < 1μm 3 (Alfa-Aesar); PTFE: 100 nm (DuPont, PTFE 9002-84-0, type MP 1500J). The mixed powders were ball milled in the SPEX 800 mill for 2-10 minutes using alumina balls with a 1:5 mass ratio of balls to powder to break down the agglomeration of powders. Table I shows the density of vari...

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“…4 was about 3.75 ms. Compared with general explosives, this reactive material has a lower reaction rate [33][34][35]. The reaction process of the reactive material was closer to high-speed combustion.…”

Section: Drop Hammer Test Of Ptfe/al/cuo Reactive Materialsmentioning

confidence: 95%

Experimental Study of Mechanical Properties and Impact-Induced Reaction Characteristics of PTFE/Al/CuO Reactive Materials

2019

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Metal/fluoropolymer materials are typical reactive materials. Polytetrafluoroethylene (PTFE)/Al/CuO reactive materials were studied in this research. Scanning electron microscopy (SEM), quasi-static compression, the Split Hopkinson pressure bar test, and the drop hammer test were used to study the mechanical properties and induced reaction characteristics of the reactive materials with different Al/CuO thermite contents and different particle sizes. SEM images of the samples demonstrate that the reactive materials were mixed evenly. The compression test results show that, if the particle size of PTFE was too small, the strength of reactive materials after sintering was reduced. After sintering, with the increase in the content of Al/CuO thermite, the strength of the micro-sized PTFE/Al/CuO firstly increased and then decreased. The Johnson-Cook constitutive model can be used to characterize the reactive materials, and the parameters of the Johnson-Cook constitutive model of No. 3 reactive materials (PTFE/Al:Al/CuO = 3:1) were obtained. The reliability of the parameters was verified by numerical simulation. Drop hammer tests show that the addition of Al/CuO aluminothermic materials or the use of nano-sized PTFE/Al reactive materials can significantly improve the sensitivity of the material. The research in this paper can provide a reference for the preparation, transportation, storage, and application of reactive materials.found that adding a high-strength metal material, such as W, with a similar particle size to the PTFE/Al reactive material, can effectively increase the strength of the reactive materials. Cai et al. [12] used a drop hammer to find that the W particle-PTFE interface separation provided initiation and propagation of cracks. In general, the addition of W can increase the strength of the reactive material but reduce the energy density. Thus, people considered adding materials that can release energy, such as Ni. After adding Ni to PTFE/Al, Wu et al. [16] found that Ni makes the reactive material brittle, but it can increase the strain-hardening modulus and compressive strength of the material, while the heat released by the material also increased. However, the energy density of PTFE/Al reactive material is very high, and the energy of PTFE/Al reactive material cannot be significantly increased by adding Ni. If the energy release efficiency of the PTFE reactive materials can be effectively improved, it will be beneficial for their application. PTFE filler metal is a very common type of engineering material. The C-F bonds in PTFE are usually stable and do not react with metals. Under high-temperature conditions, PTFE rapidly decomposes into small-molecule fluorides and undergoes a rapid exothermic reaction with active metals [18]. Experiments by Ames [19] showed that, when the PTFE/Al reactive material impacts the target at a velocity of 1.2 km/s, the energy release efficiency still does not exceed 20%. Therefore, one of the biggest problems with PTFE/Al reactive materials is that the energy release ...

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Study of the impact sensitivity of aluminum-polytetrafluoroethylene layered compositions

Cited by 10 publications

References 2 publications

Particle size effect on strength, failure, and shock behavior in polytetrafluoroethylene-Al-W granular composite materials

Particle size effect on strength, failure, and shock behavior in polytetrafluoroethylene-Al-W granular composite materials

The influence of metallic particle size on the mechanical properties of polytetraflouroethylene-Al–W powder composites

Experimental Study of Mechanical Properties and Impact-Induced Reaction Characteristics of PTFE/Al/CuO Reactive Materials

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