Assessment of failure and cohesive zone length in co-consolidated hybrid C/PEKK butt joint

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Abstract

The failure mechanisms and the cohesive zone length (CZL) during fracture of a recently developed butt jointed thermoplastic composite are evaluated in this paper. The laminated skin and the web were made of AS4/PEKK. The butt joint (filler) was injection molded from 20% short AS4 filled PEKK. The skin and web were co-consolidated together with the filler to form a hybrid butt joint structure. The crack initiation and propagation in the filler and the delamination at the skin-filler interface were captured using a high-speed camera. It was found from the experimental observations that the crack initiated in the filler and then propagated towards the skin-filler interface in less than 33 μs under three-point bending. A numerical model was developed using the finite element method in ABAQUS to predict the failure and CZL. The crack initiation and progression in the filler was predicted using the Virtual Crack Closure Techniques (VCCT) and the delamination at the skin-filler interface was modelled using the cohesive surfaces. The predicted stiffness of the specimen, the location of crack initiation and propagation as well as the force drop during delamination were in good agreement with experiments. The development of CZL was critically assessed and it was found that the CZL increases during mix mode delamination. The effect of interface strength and critical energy release rate on the CZL was investigated in the parameter analysis.

Original languageEnglish
Pages (from-to)420-430
Number of pages11
JournalEngineering Structures
Volume168
DOIs
Publication statusPublished - 1 Aug 2018

Fingerprint

Fillers
Skin
Delamination
Crack initiation
Crack propagation
Crack closure
Energy release rate
High speed cameras
ABAQUS
Thermoplastics
Numerical models
Stiffness
Cracks
Finite element method
Composite materials
Experiments

Keywords

  • Butt joint
  • Co-consolidation
  • Cohesive zone length
  • Failure analysis
  • FEM

Cite this

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title = "Assessment of failure and cohesive zone length in co-consolidated hybrid C/PEKK butt joint",
abstract = "The failure mechanisms and the cohesive zone length (CZL) during fracture of a recently developed butt jointed thermoplastic composite are evaluated in this paper. The laminated skin and the web were made of AS4/PEKK. The butt joint (filler) was injection molded from 20{\%} short AS4 filled PEKK. The skin and web were co-consolidated together with the filler to form a hybrid butt joint structure. The crack initiation and propagation in the filler and the delamination at the skin-filler interface were captured using a high-speed camera. It was found from the experimental observations that the crack initiated in the filler and then propagated towards the skin-filler interface in less than 33 μs under three-point bending. A numerical model was developed using the finite element method in ABAQUS to predict the failure and CZL. The crack initiation and progression in the filler was predicted using the Virtual Crack Closure Techniques (VCCT) and the delamination at the skin-filler interface was modelled using the cohesive surfaces. The predicted stiffness of the specimen, the location of crack initiation and propagation as well as the force drop during delamination were in good agreement with experiments. The development of CZL was critically assessed and it was found that the CZL increases during mix mode delamination. The effect of interface strength and critical energy release rate on the CZL was investigated in the parameter analysis.",
keywords = "Butt joint, Co-consolidation, Cohesive zone length, Failure analysis, FEM",
author = "Ismet Baran and Warnet, {Laurent L.} and Remko Akkerman",
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Assessment of failure and cohesive zone length in co-consolidated hybrid C/PEKK butt joint. / Baran, Ismet (Corresponding Author); Warnet, Laurent L.; Akkerman, Remko.

In: Engineering Structures, Vol. 168, 01.08.2018, p. 420-430.

Research output: Contribution to journalArticleAcademicpeer-review

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AB - The failure mechanisms and the cohesive zone length (CZL) during fracture of a recently developed butt jointed thermoplastic composite are evaluated in this paper. The laminated skin and the web were made of AS4/PEKK. The butt joint (filler) was injection molded from 20% short AS4 filled PEKK. The skin and web were co-consolidated together with the filler to form a hybrid butt joint structure. The crack initiation and propagation in the filler and the delamination at the skin-filler interface were captured using a high-speed camera. It was found from the experimental observations that the crack initiated in the filler and then propagated towards the skin-filler interface in less than 33 μs under three-point bending. A numerical model was developed using the finite element method in ABAQUS to predict the failure and CZL. The crack initiation and progression in the filler was predicted using the Virtual Crack Closure Techniques (VCCT) and the delamination at the skin-filler interface was modelled using the cohesive surfaces. The predicted stiffness of the specimen, the location of crack initiation and propagation as well as the force drop during delamination were in good agreement with experiments. The development of CZL was critically assessed and it was found that the CZL increases during mix mode delamination. The effect of interface strength and critical energy release rate on the CZL was investigated in the parameter analysis.

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