Algorithms customarily used in nanoindentation equipment assume that the indentation occurs in flat surfaces, thus simplifying the local geometry and approximating material properties in curved specimens. The irregular nature of fiber tensile fracture surfaces suggests that their structural integrity is defined by the degree of lateral (interfacial) interactions that exist within the fiber microstructure. This approach leads to small errors, for all material classes including GFRP. Because this approach treats each of the component materials individually (instead of blending them into a homogeneous anisotropic material), it is possible to examine the effects of individual material properties for both the fabric and the matrix material. These values are still quite high and in the range of the highly durable Kevlar ® fibers. The studies of polymeric nanofibres fractography which have not been reviewed in the literature are also included in this study. indicate that, the dimensionless stress decrease as SCSAs get less uniform under compression and tension, and this effect becomes more apparent as strain becomes larger. The impact tests on the plain geopolymer matrix and SHGC were performed in a gravity-driven split-Hopkinson tension bar (SHTB) at strain rates of up to 300 s⁻¹. Keeping these issues in mind, this thesis focuses on a novel nanomaterial from the cellulose II allomorph, namely TENCEL® gel, its first-time in-depth physicochemical characterization and novel ways for chemical modification. This paper presents a computational approach for composite materials subjected to ballistic impact. One of the most pressing issues of today is the global waste challenge. Its tensile stress-strain response in the axial direction is linear and elastic until failure. Soft body armor is typically comprised of materials such as aramid. However, the overall deformation in the transverse directions is nonlinear and nonelastic, although it can be treated linearly and elastically in infinitesimal strain range. Copyright © 2020 The American Society of Mechanical Engineers, This site uses cookies. “Classic Split-Hopkinson Pressure Bar Testing,” ASM Handbook, Vol. Herein, the methods of ANF fabrication and their relative merits are comprehensively discussed together with the challenges and progress in the deprotonation method for preparing ANF. Interestingly, when a compressive uniaxial stress of 25 Kbar is applied along the b axis, a structural phase transition, in which the hydrogen bonds reform along one diagonal of the ab rectangle, is predicted by SCAN. Beijing Hangkong Hangtian Daxue Xuebao/Journal of Beijing University of Aeronautics and Astronautics. In recent years much interest has been shown in the factors responsible for this softening behavior particularly in regard to the implications of the loss of the stiffening action of reinforcing fillers on the mechanism of reinforcement. Parametric computational results are included to illustrate some of these effects. To improve the reliability and design of body armor, it is imperative to understand the failure modes and the degradation rates of the materials used in armor. Journal of Mechanics of Materials and Structures. The fibers were all found to have some reduction in strength at high humidity conditions, with an approximately 14% reduction for the copolymers and a 29% reduction for the homopolymer. Kevlar® has a unique combination of high strength, high modulus, toughness and thermal stability.

Efforts to evaluate the impact of environmental conditions on fiber strength is very important for the adoption of these materials in armor systems. In this respect not only better recycling and waste disposal strategies have to be developed, but also a fundamental rethinking is required aiming at the reduction of oil-derived and non-degradable plastics in everyday products. A theoretical solution was therefore derived for the contact area of a cylinder compressed between two rigid planes when the cylinder is a transversely isotropic elastic body. The transverse direction indentation modulus of a $$12\,\upmu \hbox {m}$$ of $$\hbox {Kevlar}^{\textregistered }$$ KM2 fiber was estimated as $$7.76\, \pm \,0.22$$ GPa. Due to the inclusion of vdW interaction, SCAN, PBE+rVV10L, and SCAN+rVV10 all exhibit correct bonding strain-energy curves. To download the Kevlar® Technical Guide and learn more about Kevlar® properties, please click here. Two geometry-related coefficients $$C_{0}$$ and $$C_{1}$$ were determined that facilitate simulation of fiber nanoindentations with diameters of $$d = 7, 15, 30, 40,$$ and $$50\,\upmu \hbox {m}$$ with indentation depths up to, and including, $$2\,\upmu \hbox {m}$$. The tests were accompanied by optical measurements to assess specimen deformation and multiple cracking by means of Digital Image Correlation (DIC). It has been known for many years that deformation results in softening of rubber and that the initial stress-strain curve determined during the first deformation is unique and cannot be retraced. Results from this study provide new insights into the mechanical implications of hierarchical lateral interactions and will aid the development of novel fibers with further improved mechanical performance. The powders featured low thermal conductivity, low bulk density and high acoustic absorption at low frequencies and these properties render them promising as insulating material.

Experimental Investigation of the Transverse Mechanical Properties of a Single Kevlar® KM2e Fiber, The Transverse Compression of Anisotropic Fibre Monofilaments, The Compression of Anisotropic Fibre Monofilaments: II, Stresses in Elastic Cylinders in Contact Along Generatrix, Experimental Investigation of the Stress-Stretch Behavior of EPDM Rubber with Loading Rate Effects, Determination of Shear Modulus of Single Fibers, Ogden, R. W., 2001, “Pseudo-Elasticity and Stress Softening,”. In comparison to this, wood-based semi-crystalline microfibrils feature an elastic modulus of 84 GPa (Cheng et al. The experimental values are much smaller than the computed ones, mainly due to the fact that the PPTA fiber samples used for measurements are mechanically weaker than the perfect molecular crystals considered in the simulations. Molecular spectroscopy, scanning electron microscopy, and single fiber tensile testing were performed to characterize changes in their chemical structure, tensile strength, and failure strain as a function of exposure time to different conditions.

All rights reserved. Journal of Engineering Materials and Technology, Single fiber and Fiber-based composite Rate Dependent Mechanical Response, Mechanical deformation and fracture mechanisms of polymeric fibres from the perspective of fractography – A review, PhD Thesis: Characterization and Modification of a Cellulose II Gel, Tensile behavior of strain-hardening geopolymer composites (SHGC) under impact loading, Effects of temperature and humidity on high-strength p -aramid fibers used in body armor, Effect of elevated temperature and humidity on fibers based on 5-amino-2-(p-aminophenyl) benzimidazole (PBIA), Validation of trace-based approach to elastic properties of multidirectional glass fibre reinforced composites, Different bonding type along each crystallographic axis: Computational study of poly( p -phenylene terephthalamide), Fabrication, Applications, and Prospects of Aramid Nanofiber, Hierarchical Mechanisms of Lateral Interactions in High-Performance Fibers, On the transverse indentation moduli of high-performance KM2 single fibers using a curved area function, A COMPUTATIONAL APPROACH FOR COMPOSITE MATERIALS SUBJECTED TO BALLISTIC IMPACT, A computational model for fabrics subjected to ballistic impact, A Computational Model for Fabrics Subjected to Ballistic Impact, Proceedings of the 18th International Symposium on Ballistics, Stresses in elastic cylinders in contact along a generatrix, Split-Hopkinson pressure bar testing of soft materials, The Transverse Compression of Anisotropic Fibre Monofilaments, Mechanical properties of glass and steel fibre reinforced mortar, On acoustoelasticity and the elastic constants of soft biological tissues. DuPont™, the DuPont Oval Logo, and all trademarks and service marks denoted with ™, ℠ or ® are owned by affiliates of DuPont de Nemours, Inc. unless otherwise noted. Kevlar is a heat-resistant and strong synthetic fiber, related to other aramids such as Nomex and Technora. The theory was used together with measurements of Poisson's ratio and extensional modulus to derive the transverse modulus of the filaments from the compression experiments. Furthermore, the gel was used as precursor to produce highly porous aerogels with specific surface areas of up to 423 m2/g. A novel, straightforward and generally applicable functionalization strategy was established to introduce chemical anchor groups onto never-dried cellulosic surfaces. April 2005; 127(2): 197–203. Due to their longevity, plastics contribute to global pollution and accumulate not only in the oceans and onshore, but enter as well the food chains in form of micro- and nanosized particles. Search for other works by this author on: U.S. Army Research Laboratory, Aberdeen Proving Ground, MD 21005-5066, Ballistic Impact Into Fabric and Compliant Composite Laminates, Johnson, G. R., Beissel, S. R., and Cunniff, P. M., 1999, “A Computational Model for Fabrics Subjected to Ballistic Impact,”, Johnson, G. R., Beissel, S. R., and Cunniff, P. M., 2002, “A Computational Approach for Composite Materials Subjected to Ballistic Impact,”.