Temperature dependent torsional properties of high performance fibres and their relevance to compressive strength

Mehta, Vinay R.; Kumar, Satish

doi:10.1007/bf00357332

Cited by 44 publications

(25 citation statements)

References 15 publications

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“…Based on these results, the following experiments were performed under the conditions of h i = 360°, l = 10 mm, and with a sizing agent. Figure 7 presents the experimentally measured G 23 values as a function of the tensile modulus E. This figure also plots reference values from [4,19,21,[30][31][32]. The G 23 values for each kind of fiber measured in this study were found to be comparable to the reference values.…”

Section: Resultsmentioning

confidence: 86%

“…The torsional pendulum method is the most common technique for directly measuring the torsional shear modulus G 23 of fibers [22][23][24][25][26][27][28][29][30][31][32]. In this method, a pendulum is stuck to the edge of a fiber and rotated, which twists the fiber periodically.…”

Section: Introductionmentioning

confidence: 99%

“…The shear modulus is measured from the period of torsional oscillation. The torsional pendulum method has been used to measure the shear moduli of some carbon fibers [30][31][32], and the relationship between the shear moduli and microstructure of the fibers has also been considered in some studies [30].…”

Section: Introductionmentioning

confidence: 99%

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Torsional modulus and internal friction of polyacrylonitrile- and pitch-based carbon fibers

et al. 2015

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In the present work, the torsional modulus and internal friction of different types of polyacrylonitrile (PAN)-and pitch-based carbon fibers were measured with the torsional pendulum method to evaluate the relationship between these properties and the microstructure of carbon fibers. For easier and more accurate measurement, an aluminum disk-type pendulum was used. The measured torsional moduli were comparable to the previously reported values, which indicates the validity of the proposed method. The experimental results and discussion based on Eshelby's solution and Mori-Tanaka's mean stress method revealed that the torsional modulus should have a significant relation to the volume fraction of the crystalline region in the fibers and amorphous modulus. The results imply that fibers with a smaller crystalline region and higher amorphous modulus should show a higher torsional modulus. The internal friction of the fibers increased with the torsional modulus. This suggests that the internal friction may also be related to the size of the crystalline region and that the amorphous region has greater internal friction than the crystalline region.

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Section: Resultsmentioning

confidence: 86%

Section: Introductionmentioning

confidence: 99%

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Torsional modulus and internal friction of polyacrylonitrile- and pitch-based carbon fibers

et al. 2015

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“…In the case of PBO and PBZT, the G value is about 1 GPa (Mehta and Kumar, 1994), while it increases to about 2 GPa for Kevlar (Deteresa et al, 1984) and 5.9-7 GPa for PIPD (Lammers et al, (Chae and Kumar, 2006) (left) and PBZT (Kozey et al, 1995) fibres under compression (right, top) and bending (right, bottom). Reprinted with the permission of John Wiley Sons Inc. and of Materials Research Society.…”

Section: Mechanical Propertiesmentioning

confidence: 94%

Liquid crystalline organic fibres and their mechanical behaviour

Pegoretti

Traina

2009

Handbook of Tensile Properties of Textile and Technical Fibres

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“…We will only add here that the theoretical substantiation of the recoil method in [3], which is considered one of the simplest and most frequently used methods [4][5][6], contains a maj or error and the results of this method are a function of the basic distance used to a significant degree.…”

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confidence: 99%

Strength of armos fibres in axial compression

Sidorov

Щетинин

2000

Fibre Chem

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Highly oriented aramid fibres and the construction materials made from them have high tensile mechanical indexes but their properties are much worse in axial compression. There are no sufficiently simple and objective methods for assessing the strength of individual fibres, and the information required for determining the causes of compressive failure in complexly stressed states in construction materials is thus lacking.In previous studies [1, 2], we reviewed the existing methods and gave a brief theoretical examination of the kink bands. We will only add here that the theoretical substantiation of the recoil method in [3], which is considered one of the simplest and most frequently used methods [4][5][6], contains a maj or error and the results of this method are a function of the basic distance used to a significant degree.The microcompression method [7][8][9][10][11], where almost pure longitudinal compressive stresses are created in microsamples, has been increasingly frequently used recently for studying longitudinal compression of fibres. We used an improved microsetup ( Fig. l) which allows creating pure axial compressive stresses in the individual fibre to obtain a clearer picture of axial compression of high-modulus fibres and determine the mechanical characteristics [7,8], In contrast to similar instruments [9][10][11], in our setup one end of the fibre sample 10-16 btm in diameter is held with special holder 1, in which it can be attached with an adhesive or moved freely, and on the other end by holder 4, in which it moves relatively freely without loss of stability in compression or is also attached with an adhesive. The basic difference between holders is 2.5 sample diameters. A dynamometer is mounted in holder 4. The signals from the dynamometer and motion sensor are fed to the inlet of an ADC board; a piezoelectric crystal which assigns movement is controlled from the DAC channel.The compression curves of Armos monofibres --initial and heat-treated --up to fracture were obtained with this microsetup and the kinetics of fomlation of kink bands on the real time scale was established (Fig. 2). One kink band is initially formed due to the creation of pure axial loads in the fibres, confirmed by the load--deformation curves. Figure 2 shows that the formation of a kink band in the heat-treated fibre is more pronounced than in the initial fibre. As our studies showed, this is due to the onset of loss of stability of the initial fibre, which leads to its bending and the appearance of a complex stressed state.In addition, a series of features characteristic of heat-treated fibres was also revealed [7,8]. The measurements on individual fibres from complex yam showed that the width of the slip line and the average angle between the axis ofmicrofibrils (macromolecules) in this line and the axis of the fibre for the same shear stress are constant within the limits of the error of the measurements. Although the thickness of the band varies within wide limits for fibres of the same kind, it is constant for fibre...

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Temperature dependent torsional properties of high performance fibres and their relevance to compressive strength

Cited by 44 publications

References 15 publications

Torsional modulus and internal friction of polyacrylonitrile- and pitch-based carbon fibers

Torsional modulus and internal friction of polyacrylonitrile- and pitch-based carbon fibers

Liquid crystalline organic fibres and their mechanical behaviour

Strength of armos fibres in axial compression

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