Damage tolerance and notch sensitivity of bio-inspired thin-ply Bouligand structures

Different bio-inspired Bouligand thin-ply Carbon-Fibre-Reinforced Plastic (CFRP) laminates with a pitch angle as low as 2.07∘ are realised, which is the smallest pitch angle realised in literature. The angle is therefore close angles found in biological microstructures. Low-Velocity Impact (LVI) and residual compressive strength tests determined the damage tolerance of the structures. Investigated were two different interlaminar fracture toughnesses and two different metal-Bouligand-CFRP-layups. The low pitch angle results in significantly higher residual strengths than 45∘ quasi-isotropic (QI) layups, despite the significantly lower proportion of 0∘ fibres. Higher fracture toughness and hybridisation with steel layers lead to reduced matrix damage without increasing residual compressive strength. In-plane plane tension properties are determined with a pitch angle of 2.59∘. The results reveal, that the unnotched tensile strength is significantly lower. However, only helicoidal, sub-critical matrix cracking and no delaminations occur before final failure. The sub-critical matrix cracking leads to almost no notch sensitivity and a similar open-hole-tensile strength to 45∘-QI layups despite the low number of 0∘-fibres.

Subjects

CT analysis

Failure

Hybrid

Layered structures

Microstructures

Stress concentrations

DDC Class

540: Chemie

570: Biowissenschaften, Biologie

600: Technik

620: Ingenieurwissenschaften

660: Technische Chemie

Funding Organisations

Deutsche Forschungsgemeinschaft (DFG)

More Funding Information

This work was carried out with funding from the German Research Foundation (DFG) within the project number 283641236. This financial support is gratefully acknowledged.

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https://creativecommons.org/licenses/by/4.0/

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1-s2.0-S2666682021000414-main.pdf

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5.92 MB

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Damage tolerance and notch sensitivity of bio-inspired thin-ply Bouligand structures