Application of Kevlar to parachute system design

Peterson, Carl W.; Pepper, William B.; Johnson, Donald W.; Holt, I.

doi:10.2514/3.45271

Cited by 8 publications

(3 citation statements)

References 5 publications

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“…Individual Kevlar fibers have surface features that will provide some frictional effects when the fibers are compacted. During initial loading of the fabric, the fibers of the yam are quite loosely packed and are able to slide easily, thus providing an effective I l A ratio close to the minimum of Equation 9. As the loading increases, the fibers of the yam become more closely packed, which inhibits fiber slippage and increases the effective IIA ratio.…”

Section: Discussionmentioning

confidence: 91%

“…For sample I I, the best agreement between theory and expcrimcnt occurs when the IIA of the warp and fill yarns increase with force as shown in Figure 9. We have assumed that the individual fibers of the unloaded yam arc loose enough so that no interaction between fibers occurs and IIA is equal to the minimum of Equation 9. As the yam is loaded, interaction between fibers occurs due to changing cross section and closer packing, and the effective I l A incrcascs, finally reaching the value listed in Table I.…”

Section: Discussionmentioning

confidence: 98%

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Deflection-Force Measurements and Observations on Kevlar 29® Parachute Fabrics

Ericksen

Davis

Warren

1992

Textile Research Journal

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Deflection-force relations for plain weave Kevlara fabrics have been determined under conditions of uniaxial loading. In these experiments, the loading is stopped at a given level and a portion of the fabric is encapsulated. The fabric is then unloaded, sectioned, and photographed. Measurements on the photographs reveal the changes in weave geometry and yam cross section with loading. The initial geometrical data are used in a large deformation mechanical model, which couples yam bcnding and stretching effects to predict theoretical displacement-force relations for the fabric. Experimental and theoretical deflection-force curves arc in good agreement; they show that during initial loading the response is dominated by yarn bending, while for large loads the response is dominated by yarn stretching.The high tenacity of yam spun from Kcvlar 2g9 fibers make it an attractive material for use in parachute decelerator applications where reduced weight and bulk are particularly important. When Kevlar was first considercd for parachute applications, Coskrcn and Abbott [2] pointed out that replacing nylon with Kevlar on an equal-strength basis results in a 67% reduction in weight and a 75% reduction in volume. Extensive use of Kevlar in high performance ribbon parachutes has generally supported these predictions [8, 91. Nylon is a relatively efficient parachute material, so the degree to which the potential of Kevlar can be achieved is contingent on the effective translation of beneficial fiber mechanical properties into the mechanical properties of the textile structure.The design of parachute fabrics has been primarily a trial-and-error process in the absence of any ihcoretical models that effectively relate the overall fabric mechanical properties to specific aspects of the fabric microstructure and morphology. A number of experimental investigations to determine the effects of specific fabric microstructure on the ultimate strength of woven Kevlar fabrics have been reported. These have included studies of the effects of both warp and fill yam spacing, denier, and strcngth [ 1,3,4] on the overall fabric strength when loaded uniaxially in the warp direction. These studies have also included investigations into the strength ofjointssewn into these fabrics. ' This work was done at Sandia National Lnboratories and s u p ported by the U.S. Dtpanment of Energy undcrcontna # DE-AW-76DPW789. The effects of moisture on the strength of Kevlar 29 parachute fabrics have been investigated by Ericksen and Orear [ 5 ] . An excellent summary of the analysis of mechanical properties of general woven fabrics prior to 1969 is included in the monograph by Hearle, Grosberg, and Backer 171.In this paper, we provide deflection-force measurements obtained on three different plain weave fabrics woven from Kevlar 29 yarns. Each of the three fabrics was tested with an Instron testing machine under conditions of uniaxial loading in both warp and fill dircctions to providc a total of six deflection-force curves. In each of these six cases, four sep...

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Section: Discussionmentioning

confidence: 91%

Section: Discussionmentioning

confidence: 98%

Deflection-Force Measurements and Observations on Kevlar 29® Parachute Fabrics

Ericksen

Davis

Warren

1992

Textile Research Journal

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“…Many studies can be found on predicting fabric strength. These studies in general have concentrated on matters relating to the canopy of parachutes [1][2][3][4][5][6][7][8][9]. Edberg [1] studied the stress-strain curves of ultraviolet-aged nylon parachute fabrics where as Ericksen [4] studied the effects of folding on the strength of parachute materials.…”

mentioning

confidence: 99%

Predicting the Seam Strength of Notched Webbings for Parachute Assemblies Using the Taguchi's Design of Experiment and Artificial Neural Networks

Önal

Zeydan

Korkmaz

2009

Textile Research Journal

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Webbings are used in parachute assemblies as reinforcing units for the strength they provide. The strength of these seams is an important characteristic which has a substantial influence on the mechanical property of the parachute assemblies. It is well established that factors such as fabric width, folding length of joint, seam design and seam type will all have an impact on seam strength. In this work, the effect of these factors on seam strength was studied using both Taguchi's design of experiment (TDOE) as well as an artificial neural network (ANN). In TDOE, two levels were chosen for the factors mentioned above. An L8 design was adopted and an orthogonal array was generated. The contribution of each factor to seam strength was analyzed using analysis of variance (ANOVA) and signal to noise ratio methods. From the analysis it was found that the fabric width, folding length of joint and interaction between the folding length of joint and the seam design affected seam strength significantly. Further, using TDOE, an optimal configuration of levels of factors was found. In order to contrast and compare the results from TDOE, an ANN was also used to predict seam strength using the above mentioned factors as inputs. The prediction from TDOE and ANN methodologies were compared with physical seam strength. It was established from these comparisons, in which the root mean square error was used as an accuracy measure, that the predictions by ANN were better in accuracy than those predicted by TDOE.

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