Auxetic+Materials

5. __ Auxetic Materials: __ 5.1) ** Characterizes the material from other smart and ordinary materials: ** Auxetics are materials that have a negative Poisson's ratio. When stretched, they become thicker perpendicular to the applied force. This occurs due to their hinge-like structures, which flex when stretched. Auxetic materials can be single molecules or a particular structure of macroscopic matter. Such materials are expected to have mechanical properties such as high energy absorption and fracture resistance.

An Explaining video media type="youtube" key="vdkYuLsT7Sc" width="425" height="350"

5.2) ** The **** history of the material: ** Scientists have known about auxetic materials for over 100 years, but have only recently given them special attention. The earliest published example of a synthetic auxetic material was in Science in 1987, entitled "Foam structures with a Negative Poisson's Ratio” by R.S. Lakes from the University of Iowa. The use of the word auxetic to refer to this property probably began in 1991. The term auxetic derives from the Greek word αὐξητικός (auxetikos) which means "that which tends to increase" and has its root in the word αὔξησις, or auxesis, meaning "increase" (noun). This terminology was coined by Professor Ken Evans of the University of Exeter.

5.3) Advantages do auxetic materials offer:
Apart from the scientific value of having materials with a negative Poisson`s ration, auxetic materials show enhanced mechanical properties such as: Which make them superior to classical materials for many practical applications.
 * increased shear stiffness
 * increased plane strain fracture toughness
 * increased indentation resistance

5.4) ** Current industrial applications of the material: ** 5.4.1) ** Biomedical Industry: ** Key areas of application are seen in the biomedical field. Prosthetic materials, surgical implants, suture/muscle/ligament anchors and a dilator to open up blood vessels during heart surgery are all possible. Another area relates to the use of auxetic materials in piezoelectric sensors and actuators. Auxetic metals could be used as electrodes sandwiching a piezoelectric polymer, or piezoelectric ceramic rods could be embedded within an auxetic polymer matrix. These are expected to increase piezoelectric device sensitivity by at least a factor of two, and possibly by ten or a hundred times. The development of auxetic materials for micro- and nano-mechanical and electromechanical devices is also being investigated. 5.4.2) ** Filters: ** Auxetic foam and honeycomb filters offer enhanced potential for cleaning fouled filters, for tuning the filter effective pore size and shape, and for compensating for the effects of pressure build-up due to fouling. These benefits rely on the pores opening up both along and transverse to the direction of a tensile load applied to an auxetic filter. The pores of a non-auxetic filter open up in the stretching direction but close up in the lateral direction, leading to poorer filter performance. However, stretching an auxetic filter improves performance by opening pores in both directions. The effect of stretching on the de-fouling of an auxetic polymeric honeycomb fouled with glass beads has been investigated. For the particular honeycomb studied the value of n is dependent on the stretching direction. The studies clearly demonstrate that de-fouling is enhanced when the filter is loaded in the direction with the largest negative v.

5.4.3) ** Auxetic Fibers: ** The breakthrough development of a continuous process to produce auxetic materials in fibrous form has created the opportunity to apply their unique characteristics in a wide range of applications previously not possible. Fibers can be used in single or multiple filament structures and can be used to produce a woven structure. Typical performance characteristics expected of auxetic fibers and structures are detailed in the table of applications, (table 1), together with a list of the applications in which these characteristics could offer significant benefits. For example, by analogy with the filter de-fouling scenario of __figure__ 4, biomedical fibrous drug-release materials could be made from auxetic fibres. Extending the fibers opens the microspores and a specific dose of drug is released. Advanced auxetic fibers will include multi-filament yarns in which an auxetic filament is wrapped with one or more other yarns, perhaps high stiffness/strength, dye able or conductive filaments, so that the benefits of the auxetic material are combined with other beneficial properties for smart technical textiles applications. This will lead to the possibility of hierarchical composites displaying auxetic behavior at more than one length scale. Current research on auxetic composites is concentrated on the use of non-auxetic constituents and so benefits due to the auxetic effect occur at a macro structural level. Employing auxetic fibers as the reinforcement will enable benefits, such as impact energy and acoustic energy absorption, to be achieved at the micro structural level.

|| Application Pull-Out Resist. || Fiber Fracture Tough || Energy Absorb. || Densif. & Indent. Resist || Impact Resist || Auxetic fiber reinforcement in composites || **X ** || **X ** || **<span style="color: #333333; font-family: Verdana,sans-serif; font-size: 8pt;">X ** || **<span style="color: #333333; font-family: Verdana,sans-serif; font-size: 8pt;">X ** || **<span style="color: #333333; font-family: Verdana,sans-serif; font-size: 8pt;">X ** || <span style="color: #333333; display: block; font-family: Verdana,sans-serif; font-size: 8pt; text-align: center;">Crash helmets, body armor, sports clothing ||  ||   || **<span style="color: #333333; font-family: Verdana,sans-serif; font-size: 8pt;">X ** || **<span style="color: #333333; font-family: Verdana,sans-serif; font-size: 8pt;">X ** || **<span style="color: #333333; font-family: Verdana,sans-serif; font-size: 8pt;">X ** || <span style="color: #333333; display: block; font-family: Verdana,sans-serif; font-size: 8pt; text-align: center;">Woven structures using auxetic fibers ||  ||   ||   ||   ||   || <span style="color: #333333; display: block; font-family: Verdana,sans-serif; font-size: 8pt; text-align: center;">Micro porous hollow auxetic structures ||  ||   ||   ||   ||   || <span style="color: #333333; display: block; font-family: Verdana,sans-serif; font-size: 8pt; text-align: center;">High strength, lower weight ||  || **<span style="color: #333333; font-family: Verdana,sans-serif; font-size: 8pt;">X ** ||   ||   ||   || <span style="color: #333333; display: block; font-family: Verdana,sans-serif; font-size: 8pt; text-align: center;">Enhanced abrasion properties & entrapment of fire retardant components ||  ||   || **<span style="color: #333333; font-family: Verdana,sans-serif; font-size: 8pt;">X ** || **<span style="color: #333333; font-family: Verdana,sans-serif; font-size: 8pt;">X ** ||   || <span style="color: #333333; display: block; font-family: Verdana,sans-serif; font-size: 8pt; text-align: center;">Controlled release of drugs ||  ||   ||   ||   ||   || <span style="color: #333333; display: block; font-family: Verdana,sans-serif; font-size: 8.5pt; text-align: center;">Prevents swelling of wound by application of wound healing agent ||  ||   ||   ||   ||   ||
 * Table 1 (Part A). ** Application-performance characteristic matrix for auxetic fibers and auxetic fiber based structures.
 * <span style="color: white; display: block; font-family: Verdana,sans-serif; font-size: 8pt; text-align: center;">Fiber
 * **<span style="color: #333333; font-family: Verdana,sans-serif; font-size: 8pt;">Composite Materials **
 * **<span style="color: #333333; font-family: Verdana,sans-serif; font-size: 8pt;">Personal Protection Clothing **
 * **<span style="color: #333333; font-family: Verdana,sans-serif; font-size: 8pt;">Filtration **
 * **<span style="color: #333333; font-family: Verdana,sans-serif; font-size: 8pt;">Mechanical Lungs **
 * **<span style="color: #333333; font-family: Verdana,sans-serif; font-size: 8pt;">Ropes, Cords & Fishnets **
 * **<span style="color: #333333; font-family: Verdana,sans-serif; font-size: 8pt;">Upholstery Fabrics **
 * **<span style="color: #333333; font-family: Verdana,sans-serif; font-size: 8pt;">Biomedical **
 * **<span style="color: #333333; font-family: Verdana,sans-serif; font-size: 8.5pt;">Medical Bandages **
 * **<span style="color: #333333; font-family: Verdana,sans-serif; font-size: 8pt;">Fibrous Seals ** ||  ||   || **<span style="color: #333333; font-family: Verdana,sans-serif; font-size: 8pt;">X ** || **<span style="color: #333333; font-family: Verdana,sans-serif; font-size: 8pt;">X ** || **<span style="color: #333333; font-family: Verdana,sans-serif; font-size: 8pt;">X ** ||

|| <span style="color: #ffffff; font-family: Verdana,sans-serif; font-size: 8pt;">Application <span style="color: #ffffff; display: block; font-family: Verdana,sans-serif; font-size: 8pt; text-align: center;">Entrapped <span style="color: #ffffff; display: block; font-family: Verdana,sans-serif; font-size: 8pt; text-align: center;">Particles || <span style="color: #ffffff; display: block; font-family: Verdana,sans-serif; font-size: 8pt; text-align: center;">Wear <span style="color: #ffffff; display: block; font-family: Verdana,sans-serif; font-size: 8pt; text-align: center;">Resist. || <span style="color: #ffffff; display: block; font-family: Verdana,sans-serif; font-size: 8pt; text-align: center;">Micro porous <span style="color: #ffffff; display: block; font-family: Verdana,sans-serif; font-size: 8pt; text-align: center;">Breathable <span style="color: #ffffff; display: block; font-family: Verdana,sans-serif; font-size: 8pt; text-align: center;">Structure || <span style="color: #ffffff; display: block; font-family: Verdana,sans-serif; font-size: 8pt; text-align: center;">Constant <span style="color: #ffffff; display: block; font-family: Verdana,sans-serif; font-size: 8pt; text-align: center;">Pressure <span style="color: #ffffff; display: block; font-family: Verdana,sans-serif; font-size: 8pt; text-align: center;">Structure || <span style="color: #333333; display: block; font-family: Verdana,sans-serif; font-size: 8pt; text-align: center;">Auxetic fiber reinforcement in composites ||  ||   ||   ||   || <span style="color: #333333; display: block; font-family: Verdana,sans-serif; font-size: 8pt; text-align: center;">Crash helmets, body armor, sports clothing ||  ||   || **<span style="color: #333333; font-family: Verdana,sans-serif; font-size: 8pt;">X ** || **<span style="color: #333333; font-family: Verdana,sans-serif; font-size: 8pt;">X ** || <span style="color: #333333; display: block; font-family: Verdana,sans-serif; font-size: 8pt; text-align: center;">Woven structures using auxetic fibers || **<span style="color: #333333; font-family: Verdana,sans-serif; font-size: 8pt;">X ** ||  || **<span style="color: #333333; font-family: Verdana,sans-serif; font-size: 8pt;">X ** || **<span style="color: #333333; font-family: Verdana,sans-serif; font-size: 8pt;">X ** || <span style="color: #333333; display: block; font-family: Verdana,sans-serif; font-size: 8pt; text-align: center;">Micro porous hollow auxetic structures || **<span style="color: #333333; font-family: Verdana,sans-serif; font-size: 8pt;">X ** ||  || **<span style="color: #333333; font-family: Verdana,sans-serif; font-size: 8pt;">X ** ||   || <span style="color: #333333; display: block; font-family: Verdana,sans-serif; font-size: 8pt; text-align: center;">High strength, lower weight ||  || **<span style="color: #333333; font-family: Verdana,sans-serif; font-size: 8pt;">X ** ||   ||   || <span style="color: #333333; display: block; font-family: Verdana,sans-serif; font-size: 8pt; text-align: center;">Enhanced abrasion properties & entrapment of fire retardant components || **<span style="color: #333333; font-family: Verdana,sans-serif; font-size: 8pt;">X ** || **<span style="color: #333333; font-family: Verdana,sans-serif; font-size: 8pt;">X ** ||  ||   || <span style="color: #333333; display: block; font-family: Verdana,sans-serif; font-size: 8pt; text-align: center;">Controlled release of drugs || **<span style="color: #333333; font-family: Verdana,sans-serif; font-size: 8pt;">X ** ||  || **<span style="color: #333333; font-family: Verdana,sans-serif; font-size: 8pt;">X ** ||   || <span style="color: #333333; display: block; font-family: Verdana,sans-serif; font-size: 8.5pt; text-align: center;">Prevents swelling of wound by application of wound healing agent || **<span style="color: #333333; font-family: Verdana,sans-serif; font-size: 8pt;">X ** ||  || **<span style="color: #333333; font-family: Verdana,sans-serif; font-size: 8pt;">X ** || ====<span style="color: #333333; font-family: Verdana,sans-serif; text-align: center;">X ==== ||
 * Table 1 (Part B). ** Application-performance characteristic matrix for auxetic fibers and auxetic fiber based structures.
 * <span style="color: #ffffff; display: block; font-family: Verdana,sans-serif; font-size: 8pt; text-align: center;">Release
 * **<span style="color: #333333; font-family: Verdana,sans-serif; font-size: 8pt;">Composite Materials **
 * **<span style="color: #333333; font-family: Verdana,sans-serif; font-size: 8pt;">Personal Protection Clothing **
 * **<span style="color: #333333; font-family: Verdana,sans-serif; font-size: 8pt;">Filtration **
 * **<span style="color: #333333; font-family: Verdana,sans-serif; font-size: 8pt;">Mechanical Lungs **
 * **<span style="color: #333333; font-family: Verdana,sans-serif; font-size: 8pt;">Ropes, Cords & Fishnets **
 * **<span style="color: #333333; font-family: Verdana,sans-serif; font-size: 8pt;">Upholstery Fabrics **
 * **<span style="color: #333333; font-family: Verdana,sans-serif; font-size: 8pt;">Biomedical **
 * **<span style="color: #333333; font-family: Verdana,sans-serif; font-size: 8.5pt;">Medical Bandages **
 * =====<span style="color: #333333; font-family: Verdana,sans-serif; text-align: center;">Fibrous Seals ===== ||  || **<span style="color: #333333; font-family: Verdana,sans-serif; font-size: 8pt;">X ** ||   || **<span style="color: #333333; font-family: Verdana,sans-serif; font-size: 8pt;">X ** ||

5.5) ** Links to external material for further readings: ** For: Types Of Materials Can Exhibit Auxetic Behavior

<span style="background-color: white; font-family: Calibri,sans-serif; font-size: 14pt;">Production of Auxetic Materials
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5.1) 2 December 2011 .Retrieved February 26, 2012 ,from [] Retrieved February 26, 2012,from [|www.youtube.com] 5.2)<span style="color: #616161; font-family: Verdana,sans-serif; font-size: 8.5pt;">Mar 9, 2001 2 December 2011 <span style="color: #616161; font-family: Verdana,sans-serif; font-size: 8.5pt;">Mar 9, 2001 <span style="color: #616161; font-family: Verdana,sans-serif; font-size: 8.5pt;">Mar 9, 2001 .Retrieved February 26, 2012, from [] 5.3) J.N. Grima, March 2000. Retrieved February 26, 2012, from []  5.4.1), 5.4.2) &5.4.3) P.J. Stott, R. Mitchell, K. Alderson and A. Alderson. March 9, 2001. **<span style="color: #616161; font-family: Verdana,sans-serif; font-size: 15pt;">Auxetic Materials - An Introduction ** Auxetic material-introduction. Retrieved February 26, 2012, from **<span style="color: #616161; font-family: Verdana,sans-serif; font-size: 15pt;">Auxetic Materials - An Introduction **<span style="color: #616161; font-family: Verdana,sans-serif; font-size: 8.5pt;">Mar 9, 2001 Mar 9, 2001 []
 * References: **
 * <span style="color: #616161; font-family: Verdana,sans-serif; font-size: 15pt;">Auxetic Materials - An Introduction **
 * Done by :Fady Nagy**