A notched coupon approach for tensile testing of braided composites

Kohlman, Lee W.; Bail, Justin L.; Roberts, Gary D.; Salem, Jonathan A.; Martin, Richard E.; Binienda, Wieslaw K.

doi:10.1016/j.compositesa.2011.12.013

Cited by 27 publications

(25 citation statements)

References 6 publications

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“…Hence, a reduction of stiffness and strength can be observed compared to unidirectional composites. The inherent textile nature, which includes a multitude of curved yarn interfaces, resin rich areas and nesting of multiple plies, yields a complex 15 damage and failure behaviour. In addition, the manufacturing process creates a heterogeneous fibre assembly which can cause significant variations of the material properties across a braided composite structure.…”

Section: Introductionmentioning

confidence: 99%

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Damage and failure of triaxial braided composites under multi-axial stress states

Wehrkamp-Richter

Hinterhölzl

Pinho

2017

Composites Science and Technology

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Damage and failure of triaxial braided composites under multi-axial stress states was investigated. In order to introduce different multi-axial stress states in the material, uni-axial tensile tests were performed at different off-axis orientations. Three braid architectures, comprising braiding angles of 30 • , 45 • and 60 • were each loaded parallel to their axial, transverse and braid yarn direction. Digital image correlation measurement techniques were used to quantify the effects of the textile architecture and its heterogeneity on the strain field, to identify and locate constituent failure mechanisms and to investigate damage initiation and development. In order to identify the driving physical mechanisms behind the material non-linearity, the evolution of the damage variable and the accumulated inelastic strain was quantified using incremental loading/unloading experiments. A high-speed camera was employed in order to study the dynamic nature of catastrophic failure. The triaxial braids within this study exhibited severe non-linearities in the mechanical response before final failure as a result of extensive matrix cracking. While we found the underlying textile architecture to slightly reduce the elastic properties compared to equivalent tape laminates, it functions as a natural crack arresting grid. As a result of this mechanism, braids under certain load conditions were capable of withstanding a higher strain to failure, even if a large portion of the specimen surface was saturated with matrix cracks. The accompanying mechanical behaviour can be desirable in the design of crash absorbing or pseudo-ductile materials. An additional failure mode intrinsic to the textile architecture was encountered for loading in the heavily undulated braid yarn direction. Due to yarn straightening and out-of-plane movements, braided composites were found to fail as a result of large scale delaminations accompanied by progressive fibre bundle pull-out.

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Section: Introductionmentioning

confidence: 99%

“…[7] and [15] highlighted differences in damage propagation for straight-sided and tubular specimens due to edge-initiated failure of a 60 • triaxial braided composite subjected to transverse tension. A notched coupon geometry was proposed which yielded significantly larger strengths in relation to the standard tests.…”

mentioning

confidence: 99%

Damage and failure of triaxial braided composites under multi-axial stress states

Wehrkamp-Richter

Hinterhölzl

Pinho

2017

Composites Science and Technology

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“…The mechanical properties for the room condition correlate well with properties and trends presented in previous studies. 11,18,32 Unlike the transverse tension direction, the axial tensile results show that the environmental conditions affect the failure strength and Poisson's ratio with minimal effect on the elastic modulus. No significant difference was observed between the hot and hot/wet conditions.…”

Section: Resultsmentioning

confidence: 99%

Mechanical properties and damage characterization of triaxial braided composites in environmental conditions

Johnston

Liu

Fard

et al. 2016

Journal of Composite Materials

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Under environmental conditions, triaxial braided composites exhibit complex behavior and damage mechanisms. This paper investigates the damage mechanisms of these complex composites under varying environmental conditions. Tensile, compressive, and shear specimens of triaxial braided composite material were tested at room, hot (100 C), and hot/wet conditions (60 C/90% relative humidity). The strain field was studied using a digital image correlation system and the effect that the specimens' edges have on the strain field was quantified. For the tension specimens, the environmental conditions caused reductions in the elastic and failure properties, whereas the compression specimens exhibited degradation exclusively in the failure properties. An increase in temperature rather than humidity was found to be a driving factor for the degradation of the mechanical properties. A non-destructive, flash thermography technique was used to characterize surface/subsurface damage in the specimens. Scanning electron microscopy was conducted to determine the microstructural modes of failure.

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“…The specimens of dimensions 250mmx25mmx14mm were used for analysis in accordance with ASTM D3039 for constant headspeed tests 'Standard Test Method for Tensile Properties of Polymer Matrix Composite Materials' [24] As shown on Figure.2 The force was applied until the failure of the sample and stress-strain curve was obtained. The tensile strengths were calculated through the formula: …”

Section: Tensile Strength Testmentioning

confidence: 99%

Mechanical and durability characteristics of externally GFRP reinforced unsaturated polyester polymer concrete

Bouguessir

Harkati

Rokbi

et al. 2017

IOP Conf. Ser.: Mater. Sci. Eng.

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Abstract. The last decades of the XXe century cognized a huge extent of composite materials uses to almost all everyday life's applications, replacing the conventional materials, due to their outstanding properties especially highest strength-to-weight ratio and the ability to be designed to satisfy specific performance requirements. To get the most out of these wonder materials, a new concept, combining polymer concrete and composite laminates, is currently used in Algeria. This research work has the aim to investigate applicability of this concept in civil engineering through tensile and bending tests. On the other hand, the influence of various chemicals (Sodium hydroxide, Potassium Hydroxide and Calcium Carbonates) on our material and its tensile properties retention over long-time exposure was examined. The mechanical properties obtained indicate the convenience of this material for use in civil engineering thanks to its very good tensile and flexural performances in addition to its sufficient residual strength after theoretically 56 years.

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A notched coupon approach for tensile testing of braided composites

Cited by 27 publications

References 6 publications

Damage and failure of triaxial braided composites under multi-axial stress states

Damage and failure of triaxial braided composites under multi-axial stress states

Mechanical properties and damage characterization of triaxial braided composites in environmental conditions

Mechanical and durability characteristics of externally GFRP reinforced unsaturated polyester polymer concrete

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