High Stress Elastic Materials
parameters extending down to the strand level both experimentally and analytically to determine their effects on the Julie Chen (Mech. Eng., UMass Lowell), leader; strain behavior prior-to, through and past the locking region Armand Lewis, Steven B. Warner where there is an abrupt increase in stiffness. (Textile Sciences, UMassD) We theorize that a large order of transverse strand deformaBraided textile structures do not rely on a matrix to transmit tion under fabric shear deformation is the critical phenomena load to the fibers, as in textile composites. Instead, yarns that controls resultant braid mechanical behavior. More spewithin a braid are able to cifically, we believe strand change orientation quite deformation occurs in three freely under increasing distinct stages: tension until the “locking • consolidation - a free angle” is reached, at state of fiber rearrangewhich point the structure ment within the strand, exhibits a rapid increase • compaction -a state of in stiffness. Previous fiber slip and buckling composite models, which interaction, rely heavily on a fixed • compression - a state Fabric under shear deformation, over-layed with strand cross-sections fiber orientation and volat lock-up (left) and at 1500 lbf. tension load (right) where fibers are fully ume fraction for predictconstrained against one ing mechanical properties, are therefore not valid for braided another and fiber-to-fiber contact drives overall strand textile structures where deformations can be large, causing sigdeformation. nificant changes in textile architecture. Existing models of These states appear as the zero, nonlinear and linear stiffness rope and braided structures generally assume that the structure regions of the experimental data, respectively. does not change appreciably during loading which is only Uniaxial strand compaction tests on flattened braids and appropriate for structures undergoing small strains. Comparison of Braid Test and Model Data shear deformations, capHurcules 12k carbon braid, q=60°, PL= 18.5 in, DIA=2.85 in, 64 carrier Strain measured by LVDT - Test #3 (01-APR-01, R.A.DaSilva) tured using video microsWe are developing a generalized model 1600 copy, reveal that adjacent for linear textile structures, such as parallel stand spacing and 1400 test data braided ropes, to be used in applications, fiber width and size most 1200 model data significantly affect lock-up. such as marine, that require high strain 1000 This correlates well with 800 to failure, model predictions using a 600 high toughness and elastic conditions. combination of kinematic, 400 differential geometry and Because of these complexities, we are developing a gener200 empirical load-compaction alized model for linear textile structures, such as braided 0 data for the strand (See ropes, to better understand them and modify them for 0 0.1 0.2 0.3 0.4 0.5 Graph at Left). increased toughness. Our model will allow for large strains Differential Displacement (inch) and deformations in textile architecture, such as yarn orientaLateral strand compaction behavior drives overall braid tention and compaction, for optimizing the design of novel textile sile behavior. Therefore if a compaction behavior exhibits the structures. Because most structures exhibit a stiffening desired plateau for increasing toughness, we can obtain braids response when subjected to strain in the elastic regime, we of increased toughness comComparison of Strands Comprised of chose to demonstrate the benefits of our predictive model by Hollow and Solid Fibers Under Compaction prised of these novel fibers. E-Glass (SEP-00, R.A.Dasilva) initially modeling very high toughness linear textile structures 20 In other tests, we found that that are characterized by an anonymously large strain that 18 the compaction curve for hol- 16 occurs just prior to failure. For example, stiff braided ropes as low fibers displays a knee in 14 mooring line for boats and oil-rig platforms typically have too its curve around 6 KN force 12 little “give” and must sustain high loads under large amplitude that does not appear in solid 108 waves during stormy weather. fibers of the same material 6 Currently, we are developing a gen(See Graph at Right). This is 4 Hollow Fiber eralized model of strand interaction in Solid Fiber 2 the most critical finding of our bi- and tri-axial linear braided textile 0 work thus far and has prolific 0 0.5 1 1.5 2 2.5 3 structures under uniaxial tension. Our meaning in terms of the potenCompressive Stroke (mm) methodology consists of a modular tial to improve the toughness framework constructed from interreof current braided structures such as rope and chord. We now lated building blocks representing the need to test braids of these novel yarns to substantiate our Bi-axial structure being fiber, yarn, strand and full structure levtheories. braided on mandrel. els. We studied the variation in Force (KN)
Tensile Load (lbf)
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National Textile Center Research Briefs - Materials Competency: June 2001
If overall braid deformation is a function of transverse strand deformation, then it seems reasonable that variations in fiber parameters such as size, shape, surface roughness and material composition are critical in producing braids with increased toughness. We are now studying the behavior of the single strand under transverse uniaxial compression both experimentally and analytically. Additionally, we will braid tested strands in textile structures and conduct further braid tension tests to evaluate constitutive relationships between the strand and the structure. To address each stage of strand deformation we are now using theoretical models and methods, such as percolation theory, to determine the stage transitions and numerical or finite element modeling to address the compression portion of deformation. We expect this research to not only yield valuable modeling tools for structural textile manufacturers, but to produce new hybrid structures with improved toughness and unique performance characteristics. [Contributing Graduate Student: Robert A. DaSilva (UMass Lowell)] Industry Interactions: 4 [New England Ropes,Mentis Sciences (NH), Conneaut Industries (RI), Windmill Industries] Project Web Site Address: http://m-5.eng.uml.edu/acmtrl/ntc/M98-D03.htm For Further Information 1. R. A DaSilva, J. Chen and J. A. Sherwood, Characterization and Model Development of Linear Braided Textile Structures, SAMPE Tech Conf, Detroit (Sep 2000). 2. R. A DaSilva and J. Chen, Compaction Effects in Composite Preforms, ASME-IMECE, New York (2001). 3. Atkins and Pearce, New Braid Design Spreadsheet Calculates Fiber Architecture and Aerial Weight Simplifying the Design of Braid Reinforced Composites, Supplement (1998). 4. T. M. McBride and J. Chen, Unit-Cell Geometry in Plain-Weave Fabrics During Shear Deformations, Composites Science and Technology, 57:345 (1997). 5. K. Weissenberg, The Use of a Trellis Model in the Mechanics of Homogeneous Materials" J. Text. Inst., 40:89 (1949). 6. R.S. Irwin, Chain Folding in Thermotropic Polyesters Macromolecules, 26:7125 (1993). 7. S. B. Warner, Structure and Properties of Spider Silk, AATCC Internat. Conf., 15-18 (Sep 1996). 8. S. B. Warner, Fiber Science, Prentice-Hall, Englewood Cliffs, NJ, (1995). 9. M. Seo, H. C. Wu, J. Chen, C. S. Toomey and S. Backer, Wear and Fatigue of Nylon and Polyester Mooring Lines, Textile Research Journal, 67(7):467(1997). 10. Moon Hwo Seo, Mechanical Deterioration of Synthetic Fiber Rope in a Marine Environment, Ph.D. thesis, M.I.T (1988) 11. P. T. Hsu, Fracture mechanisms of synthetic fiber ropes, PhD thesis, Mech Eng, M.I.T. (1984). 12. M. M. Toney, On the Mechanical Behavior of Twisted Synthetic Ropes, MS thesis, Mech Eng, M.I.T. (1986). 13. J. Chen, Three-Strand Rope Behavior in Tension and Torque, MS thesis, Mech Eng, M.I.T. (1988). 14. C. J. Redman and C.D. Douglas, Theoretical Prediction of the Tensile Elastic Properties of Braided Composites, 38th Intl SAMPE Symposium, Anaheim CA (May 1993).
Julie Chen, Associate Professor of Mechanical Engineering and CoDirector of the Advanced Composite Materials and Textile Research Laboratory at UMass Lowell since 1997, earned a Ph.D. from MIT in mechanical engineering in 1991, then became Assistant Professor, Aerospace and Mechanical Engineering at Boston University until 1997. Julie’s research interests include mechanical behavior and deformation of fiber structures, fiber assemblies and composite materials. M98-D3*, F00-D6*
[email protected] (978)-934-2992 http://m-5.uml.edu/chen Armand F. Lewis, a lecturer of Textile Chemistry and Environmental Science at UMass Dartmouth, joined the faculty in 1993. He earned a Ph.D. in surface chemistry from Lehigh in 1958 following a B.S. in textile chemistry from the New Bedford Textile Institute and an M.S. in chemistry from Oklahoma State. From 1959-88, Armand was in research at American Cyanamid, Lord Corp. and Kendall. His research interests include adhesion science, flock material and processes, composite materials and the fibrous wiping of surfaces by nonwoven fabrics. M98-D3, F97-D1, F98-D4, M00-D8
[email protected] (508)-999-8452 Steven B. Warner, a Professor and Chair of Textile Sciences at UMass Dartmouth since 1994, earned a Sc.D. in polymer and material science & engineering from M.I.T. in 1976. He then spent 12 years in industrial research at Hoechst-Celanese and Kimberly-Clark and 5 years on the faculty of Georgia Tech. Steve is the author of the texts: The Science and Design of Engineering Materials and Fiber Science. His research interests include fibers science, microstructure of nonwovens and fluid management in fibrous assemblies and properties. F92-G1, M95-G8*, C95-G2, M98-D1*, M98-D3, C97-G31, I99-D16, M00-D3, M00-D8, F00-D6
[email protected] (508)-999-8449
National Textile Center Research Briefs - Materials Competency: June 2001
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