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Particle size effect on strength, failure, and shock behavior in polytetrafluoroethylene-Al-W granular composite materials
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10.1063/1.3000631
/content/aip/journal/jap/104/10/10.1063/1.3000631
http://aip.metastore.ingenta.com/content/aip/journal/jap/104/10/10.1063/1.3000631

Figures

Image of FIG. 1.
FIG. 1.

Fracture detail of various samples after quasistatic testing. (a) Shear crack and (b) axial and shear cracks in the porous PTFE-Al-fine W composite sample. (c) Axial/shear and (d) axial cracks in the porous PTFE-Al-coarse W composite sample. [(e) and (f)] Kinked axial/shear cracks in the dense PTFE-Al-coarse W composite sample. All samples had identical initial dimensions of 10.44 mm diameter and 10 mm height.

Image of FIG. 2.
FIG. 2.

Quasistatic stress-strain curve of PTFE-W-Al composite materials with variation of density and particle size of W. Curve (1) shows the results of the sample with fine W particles and porosity about 14%. Curve (2) shows the results of the sample with large W particles, which was almost fully densified. Curve (3) shows the results of the sample with large W particles CIPed at a lower pressure to induce about 14% porosity.

Image of FIG. 3.
FIG. 3.

Hopkinson bar stress vs strain and strain-rate vs strain curves of a (a) porous PTFE-Al-W composite sample containing fine W particles, (b) porous PTFE-Al-W composite samples containing coarse W particles, (c) dense PTFE-Al-W composite samples containing coarse W particles, and (d) cold isostatically pressed PTFE samples.

Image of FIG. 4.
FIG. 4.

Stress vs time curves obtained in drop weight tests. (a) Curves (1) and (2) correspond to porous samples with coarse W particles. The remarkable difference between the two curves is due to the densification of the sample, shown in curve (2), before fracture. (b) Curve (1) corresponds to the densified sample with coarse W particles. Curve (2) corresponds to the porous sample with fine W particles.

Image of FIG. 5.
FIG. 5.

(a) Porous sample (sample 73), engineering strain 0.15 with lower strength containing coarse W particles post drop-weight test corresponding to curve (1) in Fig. 4(a). (b) Porous sample (sample 65), engineering strain 0.26 containing coarse W particles corresponding to curve (2) in Fig. 4(a). (c) Porous sample (sample 64), engineering strain 0.25 with fine W particles corresponding to curve (2) in Fig. 4(b).

Image of FIG. 6.
FIG. 6.

(a) PTFE-W-Al sample (sample 1) using Al particles and W particles in a PTFE matrix. (b) PTFE-W-Al sample (sample 2) using diameter Al particles and diameter W particles in a PTFE matrix.

Image of FIG. 7.
FIG. 7.

Average engineering stress at the top of the numerical sample plotted against the global strain for a sample using small W particles (sample 1, curve 1) and a sample using large W particles (sample 2, curve 2). Note the stress suddenly increases in curve 1 at 0.13 global strain while the curve 2 coincides with the results for pure CIPed PTFE (curve 3).

Image of FIG. 8.
FIG. 8.

Stress and strain distribution in sample 1 resulting from a drop-weight calculation with a constant velocity at the top boundary. The color intensity varies from light gray (0 MPa) to dark gray for the von Mises stress and 0 to for the plastic strain. The von Mises true stress distribution (a) and local effective plastic strain (b) at 0.022 global strain. The von Mises true stress distribution (c) and local effective plastic strain (d) at 0.042 global strain. The von Mises true stress distribution (e) and local effective plastic strain (f) at 0.238 global strain.

Image of FIG. 9.
FIG. 9.

Stress and strain distribution in sample 2 resulting from a drop-weight calculation with a constant velocity at the top boundary. The color intensity varies from light gray (0 MPa) to dark gray for the von Mises stress and 0 to plastic strain. The von Mises true stress distribution (a) and local effective plastic strain (b) at 0.014 global strain. The von Mises true stress distribution (c) and local effective plastic strain (d) at 0.186 global strain. The von Mises true stress distribution (e) and local effective plastic strain (f) at 0.23 global strain.

Image of FIG. 10.
FIG. 10.

Different types of metallic particle agglomerate distributions within the soft PTFE matrix (not to scale). (a) Groups of metallic particles coalesce but do not interact immediately upon loading. The interaction of these groups does not contribute to the effective elastic modulus, but may contribute to the critical failure stress as these groups interact with one another during compression testing. (b) The metallic particle force chains are highlighted by a darker color for distinction.

Image of FIG. 11.
FIG. 11.

Material configuration composite samples that will be impacted from the top boundary at an impact velocity . (a) The sample with small W particles (diameter of ). The subfigure on the left shows a more detailed view of the microstructure. (b) The sample with large W particles (diameter of ). The subfigure on the right shows a more detailed view of the microstructure. The Al particles have a diameter in both configurations.

Image of FIG. 12.
FIG. 12.

(a) Fraction of internal energies in each material during the propagation of shock wave for the numerical sample with small W particles. (b) Fraction of internal energies in each material during the propagation of a shock wave the numerical sample with large W particles.

Image of FIG. 13.
FIG. 13.

Temperature distribution in the shocked composite numerical samples at a constant impact velocity of from the top boundary. The temperature scale ranges from 300 K (light gray) to (black) for parts (a) and (b). (a) The numerical sample with small W particles at 41.5 ns after impact. (b) The numerical sample with large W particles at 38.3 ns after impact. (c) Velocity profile (averaged in the horizontal direction) of the material starting from the bottom of the numerical samples shown in parts (a) and (b). Curve (1) corresponds to the numerical sample with small W particles. Curve (2) corresponds to the numerical sample with large W particles.

Tables

Generic image for table
Table I.

Properties of various composite materials.

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Table II.

Quasistatic test results at a strain rate of for the composite materials.

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Table III.

Hopkinson bar test results at an average strain rate of for each composite material.

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Table IV.

Drop-weight tests results at an average strain rate of for each composite material.

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Table V.

Density and volume fraction of material components in tapped powders

Generic image for table
Table VI.

The mass ratio and the increase of thermal energy with respect to total internal energy increase of composite in samples with large and small W particles.

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/content/aip/journal/jap/104/10/10.1063/1.3000631
2008-11-17
2014-04-18
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752b84549af89a08dbdd7fdb8b9568b5 journal.articlezxybnytfddd
Scitation: Particle size effect on strength, failure, and shock behavior in polytetrafluoroethylene-Al-W granular composite materials
http://aip.metastore.ingenta.com/content/aip/journal/jap/104/10/10.1063/1.3000631
10.1063/1.3000631
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