The Peculiar Behavior of the Poisson's Ratio of Laminated Fibrous Composites

The low velocity impact resistance of auxetic carbon fibre laminates has been compared to that of laminates with matched through‐the‐thickness modulus, but with Poisson's ratios of near zero and positive values. Four impact loads corresponding to major events in the static indentation response were examined and damage was assessed by ultrasonic C‐scans, detailed fractography and measurement of residual properties. It was found that enhancements were seen in resistance to low velocity for the auxetic laminates, but only at low energy levels, indicating some degree of rate dependency. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

Section: Introductionmentioning

confidence: 99%

The low velocity impact response of auxetic carbon fibre laminates

Alderson

Coenen

2008

“…Several groups have considered auxetic angle ply laminate composites [2,3,5,[9][10][11][12] either theoretically, practically or both. Most of the work on fibre reinforced composites has concentrated on using carbon fibre as the reinforcement.…”

Section: Introductionmentioning

confidence: 99%

“…around ν = -0.17 [2,3,5,8,11,12]. This is achieved in the through-thickness direction by a stacking sequence of [±θ] s with the laminate construction typically considered being [±30°] s .…”

Section: Introductionmentioning

confidence: 99%

“…Incidentally, this results in a very large (greater than +1) positive Poisson's ratio in the in-plane direction. The production of larger values of negative Poisson's ratio may increase the enhancements seen in mechanical properties, though it should be noted that if an unbalanced, bi-directional laminate is considered, a value as low as ν = -0.37 has been produced by Miki and Morotsu [11]. Also, if a more anisotropic form of carbon fibre laminate is used, it is expected that the magnitude of the Poisson's ratio is increased [15].…”

Section: Introductionmentioning

confidence: 99%

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Modelling the influence of the orientation and fibre reinforcement on the Negative Poisson's ratio in composite laminates

Harkati

Bezazi

Scarpa

et al. 2007

PACS 62.20.Dc, 81.05.ZxThe variation of through-thickness Poisson's ratio with fibre type and orientation has been investigated using a specially developed Fortran program. Glass fibre/epoxy resin composites were always found to be conventional, but negative Poisson's ratio values of up to ν 13 = -0.746 were produced over certain orientation angles for Kevlar and carbon reinforcements. This underlines the need for anisotropic pre-preg material. A range of [± β/± θ] s angles were investigated for carbon fibre laminates and it was found that auxetic behaviour could be generated for β up to 45°. All the findings of this work have extended the range of laminates which can be engineered to be auxetic either by material (i.e. Kevlar as well as carbon) or by orientation (i.e. by introducing further β layers other than the 0° and 90° previously investigated).

“…Investigations into laminates made of prepregs with carbon fibers and epoxy matrix have shown that ν xz of the composite obtained at small packing angles of the layers (10°-40°) is negative [10,11]. Another method of designing biphasic composite materials incorporating stiff inclusions and a compliant matrix shown in Fig.…”

Section: Non-auxetic Inclusions (Anisotropic Auxetics)mentioning

confidence: 99%

Peculiarities of friction in auxetic composites

Шилько

Petrokovets

Pleskachevsky

2008

The adaptive mode of friction has been studied in the form of a self‐locking effect at contact deformation of isotropic and anisotropic auxetic materials featuring a negative Poisson's ratio. The effect infers that the bearing capacity of the joint raises with increasing shearing load. The stress state parameters were determined for normal indentation and compression with shear contact interaction. The contact interactions were analyzed by the finite element method for various contact profiles. Poisson's ratio was varied within the theoretically acceptable for the isotropic elastic medium values. The analogous calculations were performed for a joint with a deformed element made of anisotropic auxetic composite whose reinforcement angle was varied as a factor of elastic constants. The nonlinear dependencies of the maximum pressure, tangential stress and slippage were obtained as a function of Poisson's ratio (in the isotropic case) and reinforcement angle of the composite material. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)