High Strain and Strain-Rate Behaviour of Ptfe∕aluminuim∕tungsten Mixtures

Addiss, John; Cai, Jing; Walley, S. M.; Proud, W. G.; Nesterenko, V. F.

doi:10.1063/1.2833238

Cited by 11 publications

(13 citation statements)

References 9 publications

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“…A "soft" drop-weight test 14 was developed to allow effective testing of low strength specimens. In the test an o-ring was placed on the top of the upper anvil to reduce the mechanical oscillations in the system caused by impact of the mass to the upper anvil.…”

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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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“…This is because the disintegration of matrix is accompanied by local compaction of metal particles resisting further deformation. It should be mentioned that samples in drop weight tests were deformed to final thickness about 1 mm from initial thickness 10 mm and registered stresses did exhibit the spike at the end of the deformation 14 .…”

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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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“…Yet, the flame temperature of combusting thermites and reactive materials (RM) is scarcely reported in the literature. Other characteristics such as ignition properties, [1][2][3][4][5][6] optical properties, 7 mechanical properties, [8][9][10][11][12] and numerical simulations [13][14][15] are more commonly reported.…”

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Thermal imaging of nickel-aluminum and aluminum-polytetrafluoroethylene impact initiated combustion

Densmore

Biss

Homan

et al. 2012

Journal of Applied Physics

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Articles you may be interested inThe role of microstructure refinement on the impact ignition and combustion behavior of mechanically activated Ni/Al reactive composites Bottom-up modeling of Al/Ni multilayer combustion: Effect of intermixing and role of vacancy defects on the ignition process Investigations on the self propagating reactions of nickel and aluminum multilayered foils Combustion temperatures from impact initiated nickel-aluminum (NiAl) and aluminumpolytetrafluoroethylene (Al-PTFE) materials have been measured using a high-speed two-camera imaging pyrometer. The materials were launched with a nominal velocity of 1700 m/s into a sealed chamber. Upon impact into a steel anvil chemical reactions were initiated and a flame propagated through the chamber. The measured temperature after impact was 3600 K (NiAl) and 3300 K (Al-PTFE).

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“…They also drew the conclusion that the addition of 30 wt.% of coarse W particles improved the impact strength of the material but led to the increase of reactive activity and the decrease of perfectibility of the reaction. Other scholars also carried out in-depth study of PTFE/Al/W from other perspectives using different techniques including quasi-static and dynamic compression (both drop-weight test and SplitHopkinson Pressure Bar), scanning electron microscopy (SEM), X-ray diffraction (XRD), and differential scanning calorimetry (DSC) [5][6][7][8][9].…”

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The Mechanical and Reaction Behavior of PTFE/Al/Fe₂O₃ under Impact and Quasi-Static Compression

Huang

Fang

et al. 2017

Advances in Materials Science and Engineering

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Quasi-static compression and drop-weight test were used to characterize the mechanical and reaction behavior of PTFE/Al/Fe 2 O 3 composites. Two kinds of PTFE/Al/Fe 2 O 3 composites were prepared with different mass of PTFE, and the reaction phenomenon and stress-strain curves were recorded; the residuals after reaction were analyzed by X-ray diffraction (XRD). The results showed that, under quasi-static compression condition, the strength of the materials is increased (from 37.1 Mpa to 77.2 Mpa) with the increase of PTFE, and the reaction phenomenon occurred only in materials with high PTFE content. XRD analysis showed that the reaction between Al and Fe 2 O 3 was not triggered with identical experimental conditions. In drop-weight tests, PTFE/Al/Fe 2 O 3 specimens with low PTFE content were found to be more insensitive by high-speed photography, and a High Temperature Metal Slag Spray (HTMSS) phenomenon was observed in both kinds of PTFE/Al/Fe 2 O 3 composites, indicating the existence of thermite reaction, which was confirmed by XRD. In PTFE/Al/Fe 2 O 3 system, the reaction between PTFE and Al precedes the reaction between Al and Fe 2 O 3 .

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High Strain and Strain-Rate Behaviour of Ptfe∕aluminuim∕tungsten Mixtures

Cited by 11 publications

References 9 publications

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

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

Thermal imaging of nickel-aluminum and aluminum-polytetrafluoroethylene impact initiated combustion

The Mechanical and Reaction Behavior of PTFE/Al/Fe₂O₃ under Impact and Quasi-Static Compression

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High Strain and Strain-Rate Behaviour of Ptfe∕aluminuim∕tungsten Mixtures

Cited by 11 publications

References 9 publications

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

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

Thermal imaging of nickel-aluminum and aluminum-polytetrafluoroethylene impact initiated combustion

The Mechanical and Reaction Behavior of PTFE/Al/Fe2O3 under Impact and Quasi-Static Compression

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The Mechanical and Reaction Behavior of PTFE/Al/Fe₂O₃ under Impact and Quasi-Static Compression