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Mechanical Properties of Auxetic and Conventional Polypropylene Random Short Fibre Reinforced Composites

Uzun M.

Fibres & Textiles in Eastern Europe

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2012

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Vol. 20, no. 5 (94)

70--74

EN

In this study, prior to the production of composites, auxetic and conventional polypropylene (PP) fibres were produced by the melt spinning technique. The fibres were tested and analysed in terms of Poisson's ratio, linear density, elongation at break and tenacity. The auxetic and conventional PP stable fibre reinforced composites were fabricated by the hand lay up method. Several mechanical properties of the composites were examined, including tensile strength, Young's modulus, elongation at break, energy absorption, impact velocity and damage size. SEM analysis was also conducted to identify microscopic changes to the overall composite structures. It was found that the auxetic fibre reinforced composites (7.5% and 10%) had the highest tensile strength and the auxetic fibre reinforced composite (5%) had the highest Young's modulus. The highest energy absorption was observed for the composite made with 10% auxetic fibre loading.

PL

Włókna polipropylenowe konwencjonalne i auksetyczne były produkowane poprzez przędzenie ze stopu z zastosowaniem wytłaczarki. Włókna były badane biorąc pod uwagę masę liniową, wytrzymałość właściwą, wydłużenie przy zerwaniu oraz znak współczynnika Poissona. Po dodaniu włókien do kompozytu badano otrzymany produkt określając parametry mechaniczne m.in. wytrzymałość na zerwanie, moduł Younga, wydłużenie przy zerwaniu, absorpcję energii, wielkość zniszczenia przy określonej prędkości udaru. Przeprowadzono również badanie mikroskopowe SEM dla określenia struktury wewnętrznej. Stwierdzono, że największa wytrzymałość miały kompozyty wzmocnione polipropylenowymi włóknami auksetycznymi 7,5% i 10%, natomiast najwyższy moduł Younga miały kompozyty zawierające 5% włókien auksetycznych. Największą absorpcję energii zaobserwowano dla kompozytów wzmacnianych 10% włóknami auksetycznymi.

2

Workings of auxetic nano-materials

Yao Y. T., Uzun M., Patel I.

Journal of Achievements in Materials and Manufacturing Engineering

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2011

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Vol. 49, nr 2

585--593

EN

The human mind is consistently interested in new materials having unique properties. Recently, a relatively new field is being investigated which exhibits a negative Poisson’s ratio (NPR), and consequently are termed auxetic materials. Design/methodology/approach: One of the main reason for interest in auxetic materials is due to the possibility of enhanced mechanical properties such as shear modulus, plane strain fracture toughness and indentation resistance compared to non auxetic material. Findings: Auxetic materials were described concerning their classification, characteristic, properties and potential applications. Research limitations/implications: The paper is an overview the modelling structure and deformation mechanisms of auxetic nano-materials. Originality/value: The paper shows the possibilities of auxetic materials application resulting from their mechanical properties.

3

Mechanical behaviour of chicken quills and chicken feather fibres reinforced polymeric composites

Uzun M., Sancak E., Patel I., Usta I., Akalin M., Yuksek M.

Archives of Materials Science and Engineering

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2011

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Vol. 52, nr 2

82-86

EN

Purpose: The objective of this study is to utilise and evaluate the mechanical properties of the chicken feather quill and fibre reinforced vinylester and polyester composites. Design/methodology/approach: Prior to production of the composites, the chicken feather fibres (CFF) were cleaned, tested and analyzed in terms of physical properties; linear density and tensile behaviour. The unidirectional CFF reinforced composites were produced with vinylester and polyester resins with three fibre reinforcement loadings (2.5, 6, 10wt%). Following experiments were conducted to determine physical properties of the control (0%) and CFF reinforced composites; tensile, flexural and Charpy impact testing. Findings: It was found that the impact properties of the CFF reinforced composites are significantly better than the control composites however both the tensile and the flexural properties of the CFF reinforced composites have poorer values compared to the control composites. For the 10% CFF reinforced vinylester composite, Charpy impact value was 4.42 kgj/mm2 which was 25% higher than the control vinylester composites (3.31 kgj/mm2) and also for the 10% CFF reinforced polyester (4.56 kgj/mm2) composite had three times better impact resistance than the control composite (1.85 kgj/mm2). Practical implications: The CFF reinforced composite have potential applications due to its improved impact behaviour. Originality/value: If the poultry waste can be utilised and used any engineering applications they will be preferred due to low-cost and superior characteristics and the most importantly they will not cause ecological and health problems.

4

Mechanical properties of ultrasonic washed organic and traditional cotton yarns

Uzun M., Patel I.

Journal of Achievements in Materials and Manufacturing Engineering

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2010

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Vol. 43, nr 2

608--612

EN

Purpose: The demand of natural and eco-friendly products have undergone tremendous growth after the awareness and realization of global ecological concerns. In this study we have used a novel product (organic cotton) and a novel system (ultrasonic), both having critical importance to environmental pollution. Cotton is one of the oldest and most abundant natural, biodegradable and renewable fibres. Although numerous synthetic fibres have been produced, cotton is still the most important fibre because of its unique physical properties like durability, strength and absorbency, furthermore, only 10% of the raw weight is lost during processing. Organic farming does not have any negative impact due to its natural growing abilities, in which the seeds genetic are not modified and no chemicals such as disinfect or fertilizer are used. Ultrasonic washing has many advantages such as the extra cleanliness of textile materials, reducing process time, energy and chemicals which are used in the washing process. In addition ultrasonic agitation brings less fibre migrations than conventional washing. Design/methodology/approach: The experimental section reports on the characterization of the organic and conventional cotton that were washed by using an ultrasonic process. Both of the cotton types that used in this study were Turkish cottons and manufactured by ring spinning system. The yarn samples were applied with two different washing temperatures (30°C and 40°C) and three different washing times (10, 20 and 30 minutes). The following stage of ultrasonic and conventional washing physical properties (yarn count, twist, tensile strength, elongation etc) was investigated and comparisons were made. Findings: The investigation presented in this study indicates benefits of employing ultrasonic washing and organic cotton farming. Research limitations/implications: The properties of yarn washed with ultrasonic energy shows better properties than those of yarns washed with conventional washing technique. The results confirms that ultrasonic washing has some advantages such as less processing time, less chemical and water consumptions compared to conventional washing methods. Originality/value: Organic cotton has a potential to substitute traditional cotton providing crop harvesting cost is significantly reduced.

5

Tribological properties of auxetic and conventional polypropylene weft knitted fabrics

Uzun M., Patel I.

Archives of Materials Science and Engineering

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2010

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Vol. 44, nr 2

120-125

EN

Purpose: The wear resistance and friction reducing properties of polymer fibres can be improved with negative Poisson's ratio behaviour. Poisson's ratio is defined as the ratio of transverse contraction strain to longitudinal extension strain in the direction of stretching force. Large number of materials have positive Poisson's ratio, however there are some materials which exhibit negative Poisson's ratio, they are termed auxetic materials. Auxetic materials present unique property that they expand in all directions when they are stretched and contract when compressed. This paper has highlighted, compared and discussed the variation between the modelling, theoretical and practical differences of auxetic materials wear behaviour. Design/methodology/approach: For the purpose of this work, auxetic and conventional fibres were produced by the melt spinning mechanism using extruder. The fibres physical properties were evaluated such as Poisson's ratio, fibre count, elongation, force and tenacity. Mono-filament fibres were used for fabrication of weft knitted fabrics; plain (1x1) structure was employed for knitting fabric. The wear resistance of the knitted fabrics were tested by using Nu-Martindale Abrasion and Pilling Tester and comparison were made. Findings: The abrasive wear test results demonstrated that the auxetic based weft knitted fabrics have superior wear behaviour than the conventional fibre based weft knitted fabrics. Practical implications: The experiment showed that the auxetic material is capable of sustaining large amount of abrasion compared to conventional fabric. Originality/value: The paper compare and discusse the variation between the modelling, theoretical and practical differences of auxetic materials wear behaviour.