Loading rate effects on mode-I delamination in glass/epoxy and glass/CNF/epoxy laminated composites

Journal article (2020)

Authors

A. Ekhtiyari Iran University of Science and Technology, Structural Integrity & Composites - Aerospace Engineering
M. M. Shokrieh Iran University of Science and Technology
R.C. Alderliesten Structural Integrity & Composites - Aerospace Engineering
Research Group
Structural Integrity & Composites (Aerospace Engineering) (TU Delft)
Copyright: © 2020 A. Ekhtiyari, Mahmood M. Shokrieh, R.C. Alderliesten
DOI: https://doi.org/10.1016/j.engfracmech.2020.106908
Fracture toughness Rate effect Fiber bridging Carbon nanofibers Hybrid reinforcement Mode-I delamination
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Published Date

2020

Language

English

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Faculty

Aerospace Engineering

Department

Aerospace Structures & Materials

Research Group

Structural Integrity & Composites

Abstract

The main objective of the present study is to assess the loading rate effects on mode-I delamination growth in glass/epoxy laminated composites. Furthermore, hybrid reinforcement of these composites by incorporating carbon nanofibers (CNFs) was followed to enhance the interlaminar fracture resistance and affect its loading rate sensitivity. Experiments on DCB specimens made of glass/epoxy and glass/CNF/epoxy laminated composites were conducted by varying the loading rate from standard quasi-static testing up to 200 mm/sec crosshead speed in a servo-hydraulic test machine. More than 21% decrease was observed in the propagation fracture toughness of the glass/epoxy samples due to loading rate elevation in the studied range. Moreover, the results of the present study clearly show the benefits of CNF modification, not only in enhancing the fracture toughness but also in reducing the loading rate dependency. Adding CNFs to glass/epoxy composites caused 32.8% and 13.5% increase in the quasi-static values of the initiation- and propagation-interlaminar fracture toughness (GIC), respectively. Also, owing to CNF incorporation, the maximum drop in the propagation fracture toughness at elevated loading rates was decreased to 8%. Fractography inspections were performed to provide an in-depth explanation for the observed loading rate effects and the advantages of CNF reinforcement.