Hybrid specimens eliminating stress concentrations in tensile and compressive testing of unidirectional composites

Gergely Czél, Meisam Jalalvand, Michael R. Wisnom

Research output: Contribution to journalArticle

  • 11 Citations

Abstract

Two novel approaches are proposed for elimination of stress concentrations in tensile and compressive testing of unidirectional carbon/epoxy composites. An interlayer hybrid specimen type is proposed for tensile testing. The presented finite element study indicated that the outer continuous glass/epoxy plies suppress the stress concentrations at the grips and protect the central carbon/epoxy plies from premature failure, eliminating the need for end-tabs. The test results confirmed the benefits of the hybrid specimens by generating consistent gauge-section failures in tension. The developed hybrid four point bending specimen type and strain evaluation method were verified and applied successfully to determine the compressive failure strain of three different grade carbon/epoxy composite prepregs. Stable failure and fragmentation of the high and ultra-high modulus unidirectional carbon/epoxy plies were reported. The high strength carbon/epoxy plies exhibited catastrophic failure at a significantly higher compressive strain than normally observed.

LanguageEnglish
Pages436-447
Number of pages12
JournalComposites Part A: Applied Science and Manufacturing
Volume91
DOIs
StatePublished - 1 Dec 2016

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Stress concentration
Carbon
Composite materials
Testing
Tensile testing
Gages
Glass

Keywords

  • carbon fibres
  • delamination
  • fragmentation
  • mechanical testing
  • stress concentration
  • composites

Cite this

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abstract = "Two novel approaches are proposed for elimination of stress concentrations in tensile and compressive testing of unidirectional carbon/epoxy composites. An interlayer hybrid specimen type is proposed for tensile testing. The presented finite element study indicated that the outer continuous glass/epoxy plies suppress the stress concentrations at the grips and protect the central carbon/epoxy plies from premature failure, eliminating the need for end-tabs. The test results confirmed the benefits of the hybrid specimens by generating consistent gauge-section failures in tension. The developed hybrid four point bending specimen type and strain evaluation method were verified and applied successfully to determine the compressive failure strain of three different grade carbon/epoxy composite prepregs. Stable failure and fragmentation of the high and ultra-high modulus unidirectional carbon/epoxy plies were reported. The high strength carbon/epoxy plies exhibited catastrophic failure at a significantly higher compressive strain than normally observed.",
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Hybrid specimens eliminating stress concentrations in tensile and compressive testing of unidirectional composites. / Czél, Gergely; Jalalvand, Meisam; Wisnom, Michael R.

In: Composites Part A: Applied Science and Manufacturing, Vol. 91, 01.12.2016, p. 436-447.

Research output: Contribution to journalArticle

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