Deformation micromechanics in high-modulus fibres and composites

Andrews, M.C.; Day, Richard; Hu, Xiao; Young, Robert J.

doi:10.1016/0266-3538(93)90142-4

Cited by 41 publications

(13 citation statements)

References 11 publications

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“…Examples of such studies may be found in references 20 to 34. Kevlar fibres have been the subject of a number of these studies as single fibres, in composites and during micromechanical tests [18,24,[25][26][27][28][29][30][31][32][33][34]. There has been some confusion in the literature since some authors have not found changes in the Raman spectrum of Kevlar when the fibre was loaded [35][36].…”

Section: Introductionmentioning

confidence: 99%

“…There has been some confusion in the literature since some authors have not found changes in the Raman spectrum of Kevlar when the fibre was loaded [35][36]. These authors used high powered Argon ion lasers whereas those who found shifts used helium neon lasers [21][22][23][24][25][26][27][29][30][31][32]. It is now clear that the 488nm line of argon ion lasers causes erratic Raman peak shifts and premature failure when used to excite Raman spectra from Kevlar fibres [21].…”

Section: Introductionmentioning

confidence: 99%

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Investigation of the micromechanics of the microbond test

Day¹,

Rodrigez²

1998

Composites Science and Technology

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The microbond test is a method which is sometimes used for measuring interfacial shear strength. In the analysis of the data it is often assumed that the interfacial shear stress is constant and thus, by implication, that the strain in the fibre along the embedded fibre decreases linearly from the point of entry to the point of exit. In this paper the results of conventional microbond tests and simulated microbond tests performed under a Raman microscope on a Kevlar-49/epoxy system are reported. The conventionally performed tests show that the calculated interfacial shear strength for this system is approximately 16 MPa regardless of the position of the supporting knife edges. The strain distribution along the fibre during simulated microbond tests was studied as a function of knife edge position, interfacial area and level of load by means of Raman spectroscopy. It was found that the interfacial shear stress was not constant, as is frequently assumed, but was strongly dependent upon distance through the droplet, knife-edge position and applied load. At low loads the strain was a maximum at the point where the fibre entered the droplet and then dropped off sharply through the embedded length. This effect was enhanced when the knife-edge separation was reduced. The variation of the shape of the stress distribution was similar to that predicted by a linear finite element analysis. At higher load levels the onset of failure in the region closest to the point where the fibre entered the droplet could be observed. M1 7HS AbstractThe microbond test is a method which is sometimes used for measuring interfacial shear strength. In the analysis of the data it is often assumed that the interfacial shear stress is constant and thus, by implication, that the strain in the fibre along the embedded fibre decreases linearly from the point of entry to the point of exit. In this paper the results of conventional microbond tests and simulated microbond tests performed under a Raman microscope on a Kevlar 49/epoxy system are reported. The conventionally performed tests show that the calculated interfacial shear strength for this system is approximately 16 MPa regardless of the position of the supporting knife edges. The strain distribution along the fibre during simulated microbond tests was studied as a function of knife edge position, interfacial area and level of load using Raman spectroscopy. It was found that the interfacial shear stress was not constant, as is frequently assumed, but was strongly dependent upon distance through the droplet, knife edge position and applied load. At low loads the strain was a maximum at the point where the fibre entered the droplet and then dropped off sharply through the embedded length. This effect was enhanced when the knife edge separation was reduced. The variation of the shape of the stress distribution was similar to that predicted by a linear finite element analysis. At higher load levels the onset of failure in the region closest to the point where the fibre entered the drople...

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Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Investigation of the micromechanics of the microbond test

Day¹,

Rodrigez²

1998

Composites Science and Technology

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“…For many high-performance fibres the peak positions of certain Raman bands have been demonstrated to shift to lower wavenumber by the application of tensile stress [5][6][7][8][9]. For all the fibres used in this study there is an approximately linear shift of the peak wavenumber, , with axial fibre strain, e f .…”

Section: Single Fibre Deformation In Airmentioning

confidence: 68%

“…This is done by establishing a link between conventional strength based theory [6][7][8][9], micromechanical considerations and experimental data obtained using Raman 3 spectroscopy to follow the deformation micromechanics of the fibre/matrix interface in model composites where a matrix crack has been propagated.…”

Section: Introductionmentioning

confidence: 99%

A strength based criterion for the prediction of stable fibre crack-bridging

Bennett¹,

Young²

2008

Composites Science and Technology

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“…Since it came to market in 1972, the availability of Kevlar/Twaron aramid fibers has advanced in material science, particularly in the areas of fiber-reinforced composites, rubber goods, ropes and cables, ballistics, pulp-reinforced friction products, gaskets, and so forth. [1][2][3] However, the Twaron fiber-reinforced composites show poor interfacial adhesion between the Twaron fiber and the matrix resin, due to the low surface energy and chemically inert surface of the fiber. Therefore, the properties of the composites and their durability with regard to combined moisture and temperature attack are dependent on the interface between the above two components.…”

Section: Introductionmentioning

confidence: 98%

Direct fluorination of Twaron fiber and investigation of mechanical thermal and morphological properties of high density polyethylene and Twaron fiber composites

Maity

Jacob

Das

et al. 2007

J of Applied Polymer Sci

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Composites consisting of high density polyethylene (HDPE) reinforced with randomly oriented chopped Twaron fibers (both fluorinated and nonfluorinated) show a significant increase in mechanical and thermal properties. To increase the better fiber matrix adhesion, the Twaron fiber is surface fluorinated using elemental fluorine. The surface of the Twaron fiber becomes very rough and the diameter of Twaron fiber increases from $ 12 to 14 lm after fluorination. The composites were prepared using solution method to overcome the damage of the fiber. The tensile strength and the Young's modulus increases with increasing fiber content. The tensile strength and modulus of modified fiber (fluorinated Twaron fiber) composites is much higher than nonmodified fiber composites indicating that there is better mechanical interlocking between the modified fiber and the matrix. Thermal properties obtained from DSC and DTA-TG analysis of the fluorinated fiber composites are also improved. Contact angle measurements, as well as the surface energy measurements, indicate that the composites are more wettable and is maximum for fluorinated fiber composites i.e., surface energy for fluorinated fiber composites is highest. Crystallinity is also higher for fluorinated fiber composites.

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Deformation micromechanics in high-modulus fibres and composites

Cited by 41 publications

References 11 publications

Investigation of the micromechanics of the microbond test

Investigation of the micromechanics of the microbond test

A strength based criterion for the prediction of stable fibre crack-bridging

Direct fluorination of Twaron fiber and investigation of mechanical thermal and morphological properties of high density polyethylene and Twaron fiber composites

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