The Effect of Crystallinity on Compressive Properties of Al-PTFE

Bin, Feng; Fang, Xiang; Wang, Huai-xi; Dong, Wen; Li, Yuchun

doi:10.3390/polym8100356

Cited by 46 publications

(37 citation statements)

References 37 publications

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“…When the impact velocity is moderate such as in drop weight tests and in SHPB tests, fracture-induced hot-spots are also crucial to the ignition process for Al-PTFE. It was found that the first signs of reaction could only be observed in cracks of samples in drop weight tests (impact velocity 1 m/s~10 m/s) [25] and in SHPB tests (impact velocity 20 m/s~30 m/s) [26].…”

Section: The Applicability Of the Crack-induced Hot-spots Generation mentioning

confidence: 99%

A Mechanism of Hot‐spots Formation at the Crack Tip of Al‐PTFE under Quasi‐static Compression

Bin

Hao

et al. 2017

Propellants Explo Pyrotec

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Generally, the Al‐PTFE (polytetrafluoroethylene) is thought to be inert under quasi‐static or static loads. However, it was found that Al‐PTFE would initiate under quasi‐static compression after a specific heat treatment procedure and the opening fracture plays a crucial role in the initiation. A unique micrographic fracture pattern which showed unstable crack propagation and a ductile‐to‐brittle transition was observed at openning cracks by SEM. Combining the observed microstructure with the stress distribution at the path of crack propagation derived from numerical simulation, a mechanism was proposed to explain the formation of “hot‐spots” at the crack tip. The temperature rise at the crack tip was estimated to be at least 612 °C, which is high enough to ignite the Al‐PTFE composite.

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Section: The Applicability Of the Crack-induced Hot-spots Generation mentioning

confidence: 99%

A Mechanism of Hot‐spots Formation at the Crack Tip of Al‐PTFE under Quasi‐static Compression

Bin

Hao

et al. 2017

Propellants Explo Pyrotec

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“…Such a perspective is valid for the material subjected to roller compaction. However, it has been reported that a reduction in the true density of a material can take place when the structure undergoes a polymorphic transformation [40,41]. In this regard, changes in the molecular arrangement of a powder can result in loose packing at the particulate level.…”

Section: Discussionmentioning

confidence: 99%

Understanding the Performance of a Novel Direct Compression Excipient Comprising Roller Compacted Chitin

et al. 2020

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Chitin has been investigated in the context of finding new excipients suitable for direct compression, when subjected to roller compaction. Ball milling was concurrently carried out to compare effects from different energy or stress-inducing techniques. Samples of chitin powders (raw, processed, dried and humidified) were compared for variations in morphology, X-ray diffraction patterns, densities, FT-IR, flowability, compressibility and compactibility. Results confirmed the suitability of roller compaction to convert the fluffy powder of raw chitin to a bulky material with improved flow. X-ray powder diffraction studies showed that, in contrast to the high decrease in crystallinity upon ball milling, roller compaction manifested a slight deformation in the crystal lattice. Moreover, the new excipient showed high resistance to compression, due to the high compactibility of the granules formed. This was correlated to the significant extent of plastic deformation compared to the raw and ball milled forms of chitin. On the other hand, drying and humidification of raw and processed materials presented no added value to the compressibility and compactibility of the directly compressed excipient. Finally, compacted chitin showed direct compression similarity with microcrystalline cellulose when formulated with metronidazole (200 mg) without affecting the immediate drug release action of the drug.

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“…Finally, the samples were put into a furnace to undergo a sintering cycle under the protection of argon atmosphere. Different from the sintering processes in published researches, the maximum temperature in our sintering process was much lower while the sintering cycle was much shorter to achieve a more brittle material property [6,17,22]. Specifically, it included heating the pressed samples at a rate of about 50 °C per hour to a final temperature of 300 °C, holding at the final temperature for 6 h, and then cooling to room temperature at the rate of 50 °C per hour.…”

Section: Methodsmentioning

confidence: 96%

A Study on the Mechanical Properties and Impact-Induced Initiation Characteristics of Brittle PTFE/Al/W Reactive Materials

Maimaitituersun

Dong

et al. 2017

Materials

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Polytetrafluoroethylene/aluminum/tungsten (PTFE/Al/W) reactive materials of three different component mass ratios (73.5/26.5/0, 68.8/24.2/7 and 63.6/22.4/14) were studied in this research. Different from the PTFE/Al/W composites published elsewhere, the materials in our research were fabricated under a much lower sintering temperature and for a much shorter duration to achieve a brittle property, which aims to provide more sufficient energy release upon impact. Quasi-static compression tests, dynamic compression tests at room and elevated temperatures, and drop weight tests were conducted to evaluate the mechanical and impact-induced initiation characteristics of the materials. The materials before and after compression tests were observed by a scanning electron microscope to relate the mesoscale structural characteristics to their macro properties. All the three types of materials fail at very low strains during both quasi-static and dynamic compression. The stress-strain curves for quasi-static tests show obvious deviations while that for the dynamic tests consist of only linear-elastic and failure stages typically. The materials were also found to exhibit thermal softening at elevated temperatures and were strain-rate sensitive during dynamic tests, which were compared using dynamic increase factors (DIFs). Drop-weight test results show that the impact-initiation sensitivity increases with the increase of W content due to the brittle mechanical property. The high-speed video sequences and recovered sample residues of the drop-weight tests show that the reaction is initiated at two opposite positions near the edges of the samples, where the shear force concentrates the most intensively, indicating a shear-induced initiation mechanism.

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The Effect of Crystallinity on Compressive Properties of Al-PTFE

Cited by 46 publications

References 37 publications

A Mechanism of Hot‐spots Formation at the Crack Tip of Al‐PTFE under Quasi‐static Compression

A Mechanism of Hot‐spots Formation at the Crack Tip of Al‐PTFE under Quasi‐static Compression

Understanding the Performance of a Novel Direct Compression Excipient Comprising Roller Compacted Chitin

A Study on the Mechanical Properties and Impact-Induced Initiation Characteristics of Brittle PTFE/Al/W Reactive Materials

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