Stress-Strain Relationships in Yarns Subjected to Rapid Impact Loading

Stone, W.K.; Schiefer, Herbert F.; Fox, George

doi:10.1177/004051755502500605

Cited by 25 publications

(3 citation statements)

References 17 publications

(1 reference statement)

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“…Single filaments in the nylon fabric are independent and separated (or at least separable) 1 from each other within the yarn structure. In the impacted area, however, filaments frequently stick together and are fused into larger clumps or a compact mass, 4 Figure 13, p. 527 [10]. Figure 9A; (b) part of Figure 9B ; (c) part of Figure l0A ; (d) part of Figure IOC.…”

Section: Sectioning Technique Experimentai Proceduresmentioning

confidence: 99%

Microscopical Study of a Multilayer Nylon Body Armor Panel After Impact

Susich

Dogliotti

Wrigley

1958

Textile Research Journal

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A body armor panel consisting of twelve identical layers of 2 X 2 basket weave nylon fabric was investigated after impact by a fragment simulator .22-caliber steel missile in the range of 330-420 m. sec. (1100-1400 ft. sec.) striking velocities. The kinetic energy of the projectile was either slightly higher or lower than that the panel could absorb (706,000 g.-cm.).Completely and partially penetrated holes were investigated. The area surrounding the bullet holes was studied to learn about the various types of deformations and damages in each layer. The microscopic observations were obtained at various magnifications (5, 10, and 200 X) from cross sections of the panel and from individual layers removed from the panel.Cross sections at various levels were made in three directions, either perpendicular or parallel to the panel surface. In these sections the distortion of the fabric pattern, alignment of extended, unravelted. and broken yarns into the direction of bullet movement, compression of yarns, softening, heat relaxation, fusion, decomposition, and fibrillation of nylon filaments were observed. It was recognized that the permanent damage was localized to a small area close to the path of the fast-moving missile.After separating the panel into individual layers, the stoppage of the projectile was studied. A slight dissipation of the stress was observed in those layers which were exposed to the bullet after it was stowed down. Some damages to nylon filaments were caused by the transient and localized heat generated during the impact of the missile.Fibrillation indicates the vigorous movements of filaments which took place in the panel during penetration. The restriction of permanent deformations and defects to small regions was explained by the presence of cross yarns. They prevent the propagation oi the stress from the impacted spot to any considerable length along the yarns.

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Section: Sectioning Technique Experimentai Proceduresmentioning

confidence: 99%

Microscopical Study of a Multilayer Nylon Body Armor Panel After Impact

Susich

Dogliotti

Wrigley

1958

Textile Research Journal

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“…1) (It may be substituted by the speed of propagation langing approximately from 10 m/s to 14 .29 m/s.) (2) In general, the propagation time of tension in the yarn increases with decreasing Young' modulus of the yarn. …”

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confidence: 99%

Study on Elastic Effect of Warp Yarn During the Weaving

et al. 1966

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It is a matter of importance to discuss the elastic behavior of the warp yarn subjected to trans verse impact caused by the heald during the weaving.In the present, a description is given of the equipment built to measure the propagation time of tension in the yarn by the transverse impact loading.The following results were obtained In general, the propagation time of tension in the yarn increases with decreasing Young' modulus of the yarn.(3) This propagation time of tension in the yarn seemed to be markedly depedent upon the material of fibers in the yarn, and not dependent upon the count of yarn.

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“…Stone, Schiefer, and Fox[6] have recently described some ingenious experiments relating to the behavior of yarns under impact loading. Among other results, they show, as others had shown earlier…”

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confidence: 99%

Behavior of Yarns Subject to Impact Loading

Gruntfest¹

1955

Textile Research Journal

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Stone, Schiefer, and Fox [6] have recently described some ingenious experiments relating to the behavior of yarns under impact loading. Among other results, they show, as others had shown earlier [5], that when nylon filaments fail under these conditions the new ends have been fused. They suggest that the cause of fusion may be &dquo;... the high, localized energy released by bond rupture.&dquo; We would like to suggest that fusion or pyrolysis is rather a normal concomitant of impact failure and perhaps other types of failure as well.We have discussed the problem of the energyabsorption capacity of materials in terms of the density of strain energy and the strained volume [3]. If a material &dquo;work hardens&dquo; in response to strain, when a strain is initiated at a point it will tend to become general so that the strained volume will be large. On the other hand, if &dquo;work softening&dquo; occurs, the strained volume will remain small and the net energy absorption (the product of the energy density and the volume) will be small. We think that this point of view provides some new insight into the nature of brittleness and toughness as well as providing an explanation of the fusion that is observed in the case at hand.In the present connection, the impact test is by its nature adiabatic. A work-softening process which must be considered, therefore, is the reduction in modulus that accompanies the work-induced temperature rise. In a qualitative way the importance of this work-softening process is shown by a consideration of the temperature-modulus relationships for various materials given by Schmieder and Wolf [4].For example, polystyrene, which has a very sharp drop in modulus at the glass temperature, is a brittle material. Nylon, on the other hand, has an attenuated temperature-modulus curve that depends on the existence of crystalline regions which function as crosslinking points in the rubbery material above the glass temperature. Nylon is, of course, an excellent example of a tough substance. Other similar examples can be given, and no exceptions to this general relationship between the temperature-modulus dependence and the toughness of uncrosslinked homopolymers have been found.The implication of this argument is that failure is a local catastrophe which may involve only a small fraction of the gross sample volume. This concentration of the strain energy at the point of failure can easily lead to fusion or pyrolysis. For nylon the strained volume is sufficiently large so that the fusion is apparent on inspection. The more brittle materials may fuse over so small a volume element that special methods would have to be devised to detect it, or, indeed, local pyrolysis may be involved.The development of high local temperatures during the mechanical working of materials has been clearly shown in experiments which involve less violent processes than actual failure. For example, Brauer and Mfller [2] have found temperature rises of about 70° C occurring during the drawing of polyvinyl chloride fibers. Bowden...

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Stress-Strain Relationships in Yarns Subjected to Rapid Impact Loading

Cited by 25 publications

References 17 publications

Microscopical Study of a Multilayer Nylon Body Armor Panel After Impact

Microscopical Study of a Multilayer Nylon Body Armor Panel After Impact

Study on Elastic Effect of Warp Yarn During the Weaving

Behavior of Yarns Subject to Impact Loading

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