Search or add a thesis

Advanced Search (Beta)
Home > Development of Elastomeric Auxetic Structures for Impact Energy Absorption

Development of Elastomeric Auxetic Structures for Impact Energy Absorption

Thesis Info

Access Option

External Link

Author

Bashir, Muhammad Arshad

Program

PhD

Institute

National University of Sciences & Technology

City

Islamabad

Province

Islamabad

Country

Pakistan

Thesis Completing Year

2016

Thesis Completion Status

Completed

Subject

Applied Sciences

Language

English

Link

http://prr.hec.gov.pk/jspui/bitstream/123456789/7243/1/Muhammad_Arshad_Bashsir_Materials_%26_Surface_Engineering_2016_HSR_NUST_04.01.2017.pdf

Added

2021-02-17 19:49:13

Modified

2024-03-24 20:25:49

ARI ID

1676725872277

Asian Research Index Whatsapp Chanel
Asian Research Index Whatsapp Chanel

Join our Whatsapp Channel to get regular updates.

Similar


Elastomeric sponge and auxetic materials have unique characteristics which distinguish them from other solid materials like metals and ceramics. Such engineering materials with unique performance are a continuous requisite so as to assist the evolution for advance engineering applications. Auxetic materials (materials with negative Poisson’s ratio) have a unique feature of getting fatter when pulled and contract transversely when compressed, longitudinally. They are mainly used for their improved indentation resistance, higher fracture toughness, better thermal shock resistance, and good acoustic damping. Twenty diverse compositions were developed with various reinforcements’ incorporation such as carbon black nano particles etc., varying blending ratios of natural rubber (NR), styrene butadiene rubber (SBR), and nitrile butadiene rubber (NBR) in ethylene propylene diene monomer (EPDM). Sponge and auxetic structures were developed during vulcanization a hot isostatic biaxial hydraulic press by volumetric compression and cooling under pressure. The reinforcements were impregnated into the elastomeric matrices using internal dispersion kneader and two-rolls mixing mill. Seven types of mold geometries were designed and used as per ASTM standards to fabricate nanocomposites using a hot press in order to evaluate the elastomeric composites for rheological, mechanical, structural, vulcanization, compressive strain, dynamic mechanical thermal analysis and impact energy absorption applications. Mechanical characteristics were executed using Universal Testing Machine (UTM), Dynamic Mechanical Thermal Analyzer (DMTA) and rubber hardness tester. Scanning electron microscopy coupled with EDS were used to evaluate sponge and auxetic structures. The synthesized auxetic materials verified by scanning electron images and Poisson’s ratio determined by processing images using ‘Matlab’ software. With the advances in the fabrication and synthesis of a wider range of these thrilling materials, there is enormous potential for applications in industrial and commercial sectors. Among the various rubber systems investigated EPDM based elastomeric composites proved to be the best for development of auxetic structures. Hardness of the EPDM sponge composite with 20% incorporation of carbon black nano fillers enhanced up to 112%. EPDM with the addition of 20% carbon black attained tensile strength 142%, compared to EPDM without reinforcement; this nanocomposite also showed a 20% reduction in impact energy absorption. EPDM-30%NR reinforced with 20% carbon black showed a minimum reduction of 33% in storage modulus indicating good retention of elasticity. Maximum enhancement of 400% loss modulus was obtained in case of EPDM-30%SBR reinforced with 20% carbon black. Rheological bahaviour such as loss tangent during vulcanization enhanced up to 130%, 300%, 85%, 11% by incorporation of 30% carbon black, 30% NBR, 30% NR, and 30 % SBR.
Loading...
Loading...

Similar Books

Loading...

Similar Chapters

Loading...

Similar News

Loading...

Similar Articles

Loading...

Similar Article Headings

Loading...

جدائی

جدائی

جدائی کے نیزے پر دل تڑپتا ہے
پچھلے پہر کی ساعتوں میں!
خوشبو کے ساتھ۔۔۔ہوائیں بھیگی آنکھیں چومتی ہیں
روح البیان کی شرطوں میں۔۔۔!
خوابوں کے سوگ میں سوسن نسترن!
ثنویت کی آہٹوں میں غنا سطیت کی سانسیں سمو رہی ہیں
زرتشت، گوتم، عیسیٰؑ صدیوں پہلے۔۔۔!
دائم ’’فارقلیط‘‘ کا صحیفہ پڑھ کر سنا گئے
پھر بھی آبنائے محبت میں تیرتے بجروں کے بادباں پر۔۔۔!
اک پرندہ۔۔۔!
معصوم موسموں کے صحیفوں کی آہٹیں بولتا رہتا ہے
ہجر کے صحرا میں دل تڑپتے ہوئے!
روغن چشم سے چراغ روشن کرتے ہوئے!
معتبر علامتوں کو جدائی کی میزان پر تولتا رہتا ہے

تصوف کے غیر مشہور سلاسل کا تحقیقی جائزہ

Human being is the combination of two elements (body and soul). Soul is the eternal element in human being. Body of human is subordinate to disease and illness. Similarly soul can also get illness and inner disease. Human being visits doctors for cure and getting better physical health of body, likewise for the care and cure of the soul of human needs to have spiritual attachment, which is called tasawof. In Muslim society, it is believed that Tasawoof is confined to four categories (Salasil) i.e. Naqashbandiya, Chishtiya, Saharwardiya and Qadariya. In the same context it is also accepted that some other names of different salasil exist in different societies and books, which made the confusion in the  real picture and concept of Tasawof. This article is an attempt to find  these unfamiliar Salasil of tasawof and clarify their legal status. The researcher studied in this context which stated that tasawof is not restricted to the above mentioned four categories. The reason of less familiarization in the society is that the it was practiced by less followers at the time.

Study of High Frequency Kinetic Modes in Non-Thermal Magnetoplasma

In this thesis, we have investigated the electrostatic electron Bernstein waves in a collisionless magnetized plasma using the Cairns distribution function. In this regard, we have derived a generalized dielectric constant for the Bernstein waves and derived the modified dispersion relation in the presence of Cairns distribution function. We have found that the dispersion curves for the electron Bernstein waves using the Cairns distribution function show a very significant deviation from the Maxwellian results. It has been found that the behavior of the Bernstein waves across the entire band between the adjacent harmonics show a departure from the Maxwellian result for the different values of the non-thermality parameter for the Cairns distribution function. Furthermore, Bernstein waves with Vasyliunas-Cairns (VC) distribution has been investi gated. We have obtained the linear dispersion relation for Bernstein waves for two electron species and explored it both analytically and numerically. It has been shown that Bernstein waves with Vasyliunas-Cairns distribution exhibit a significant departure from the results re ported earlier with Maxwellian and dual kappa distributions especially in the long wavelength regime. It has been found that the parameters represent the non-thermal percentage of cold and hot electrons in Cairns distribution, play a unique and vital role in determining the behavior of Bernstein modes in VC distribution which has no parallel in Maxwellian and double kappa distribution functions. Whistler waves propagating parallel to the ambient magnetic field with electron temperature anisotropy have also been investigated employing the kinetic theory of plasmas. The electron distribution function has been considered to follow the Cairns distribution. Dispersion relation for the whistler waves with Cairns distribution has been derived and the condition for the onset of instability has also been obtained. It has been found that the Cairns distribution significantly modifies the instability condition for the growth of whistler instability. The comparison of the dispersion characteristics and growth rate with Maxwellian distribution has also been made and it has been observed that Cairns distributed electrons yield a higher growth rate by comparison with their Maxwellian counterparts. It has also been shown that unlike the kappa distribution where parallel electron beta was found to play the key role, whistler instability with Cairns distributed electrons shows a greater sensitivity towards electron temperature anisotropy. It has been shown that the real frequency of the whistler waves shows dependence on the choice of parallel electron beta. Interestingly, it has been found that a particular combination of parallel electron beta and electron temperature anisotropy is deleterious for the whistler instability. In the end, a comparison of whistler waves dispersion and growth has been done with elec tron temperature anisotropy using different non-thermal distributions by changing the plasma parameters. It has been found that the growth rate of whistler instability is maximum for flat topped distribution whereas it is minimum for the Maxwellian distribution. Our study may be beneficial to understand the propagation characteristics of waves in space plasmas where departure from Maxwellian behavior has been divulged by many expeditions in space.