## Abstract

A mixed mode specimen is proposed for fracture mechanics characterisation of

adhesive joints, laminates and multilayers. The specimen is a double cantilever

beam specimen loaded with uneven bending moments at the two free beams. By

varying the ratio between the two applied moments, the full mode mixity range

from pure mode I to pure mode II can be generated for the same specimen geometry. The specimen allows stable crack growth. In case of large scale crack

bridging, mixed mode cohesive laws can be obtained by a J integral based approach. As a preliminary example, fracture of adhesive joints between two

glass-fibre laminates was studied. The mixed mode fracture resistance increased

with increasing crack length due to fibre cross over bridging, eventually reaching a steady-state level (R-curve behaviour). The steady-state fracture toughness

level increased with increasing tangential crack opening displacement. Cohesive

stresses were determined by a J integral approach. The deducted shear stress

was found to be relative high (≈ 20 MPa) in comparison with the normal stress

(≈ 1 MPa).

adhesive joints, laminates and multilayers. The specimen is a double cantilever

beam specimen loaded with uneven bending moments at the two free beams. By

varying the ratio between the two applied moments, the full mode mixity range

from pure mode I to pure mode II can be generated for the same specimen geometry. The specimen allows stable crack growth. In case of large scale crack

bridging, mixed mode cohesive laws can be obtained by a J integral based approach. As a preliminary example, fracture of adhesive joints between two

glass-fibre laminates was studied. The mixed mode fracture resistance increased

with increasing crack length due to fibre cross over bridging, eventually reaching a steady-state level (R-curve behaviour). The steady-state fracture toughness

level increased with increasing tangential crack opening displacement. Cohesive

stresses were determined by a J integral approach. The deducted shear stress

was found to be relative high (≈ 20 MPa) in comparison with the normal stress

(≈ 1 MPa).

Original language | English |
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Place of Publication | Roskilde |
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Publisher | Risø National Laboratory |

Number of pages | 35 |

ISBN (Print) | 87-550-3186-2 |

ISBN (Electronic) | 87-550-3187-0 |

Publication status | Published - 2004 |

Series | Denmark. Forskningscenter Risoe. Risoe-R |
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Number | 1394(EN) |

ISSN | 0106-2840 |

## Keywords

- Risø-R-1394
- Risø-R-1394(EN)