Nanoscale toughening of carbon fiber reinforced/epoxy polymer composites (CFRPs) using a triblock copolymer

Nicholas T. Kamar, Lawrence T. Drzal, Andre Lee, Per Askeland

    Research output: Research - peer-reviewArticle

    • 2 Citations

    Abstract

    This work explored the incorporation of a triblock copolymer in carbon fiber reinforced epoxy polymer composites (CFRPs) to improve their mode-I fracture toughness, GIc (J/m2). The triblock copolymer poly (styrene)-block-poly (butadiene)-block-poly (methylmethacrylate) (SBM) was used to modify the CFRP matrix at 5, 10 and 15 phr concentrations, respectively. CFRPs were manufactured using an in-house sizing tower system, prepregger, vacuum bag and autoclave method. Mode-I fracture toughness testing revealed a 290% increase in GIc by incorporation of the reactive sizing on the fibers and 10 phr SBM in the matrix. Scanning electron microscopy of the SBM modified CFRP fracture surfaces showed that well distributed, sub 100 nm spherical micelles of SBM underwent cavitation and induced void growth and shear yielding toughening mechanisms to absorb fracture energy. It is noteworthy that longitudinal and transverse composite three point flexural testing showed that the SBM modified matrix did not decrease CFRP strength and stiffness up to 10 phr additive. Further, dynamic mechanical analysis revealed that SBM at 10 phr decreased the glass transition temperature (Tg) of CFRPs by only 2.9 °C; the Tg was then recovered at 15 phr SBM. Finally, the SBM modified CFRP GIc was compared to the neat matrix GIc at 0, 5, 10 and 15 phr SBM to develop a ‘transfer factor’ for SBM modified composites. It was found that only 10% of the increased matrix toughness was transferred from the SBM modified epoxy to the CFRPs. The presence of the rigid carbon fibers constrains plastic deformation of the modified epoxy and limits the toughness transfer in the composite.

    LanguageEnglish (US)
    Pages36-47
    Number of pages12
    JournalPolymer (United Kingdom)
    Volume111
    DOIs
    StatePublished - Feb 24 2017

    Profile

    Toughening
    Block copolymers
    Polymers
    Composite materials
    carbon fiber
    Carbon fibers
    Toughness
    Fracture toughness
    Testing
    Methylmethacrylate
    Transfer Factor
    Polymer matrix composites
    Styrene
    Fracture energy
    Autoclaves
    Micelles
    Dynamic mechanical analysis
    Cavitation
    Towers
    Plastic deformation

    Keywords

    • Block copolymers
    • CFRPs
    • Fracture toughness

    ASJC Scopus subject areas

    • Polymers and Plastics
    • Organic Chemistry

    Cite this

    Nanoscale toughening of carbon fiber reinforced/epoxy polymer composites (CFRPs) using a triblock copolymer. / Kamar, Nicholas T.; Drzal, Lawrence T.; Lee, Andre; Askeland, Per.

    In: Polymer (United Kingdom), Vol. 111, 24.02.2017, p. 36-47.

    Research output: Research - peer-reviewArticle

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    AU - Kamar,Nicholas T.

    AU - Drzal,Lawrence T.

    AU - Lee,Andre

    AU - Askeland,Per

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    N2 - This work explored the incorporation of a triblock copolymer in carbon fiber reinforced epoxy polymer composites (CFRPs) to improve their mode-I fracture toughness, GIc (J/m2). The triblock copolymer poly (styrene)-block-poly (butadiene)-block-poly (methylmethacrylate) (SBM) was used to modify the CFRP matrix at 5, 10 and 15 phr concentrations, respectively. CFRPs were manufactured using an in-house sizing tower system, prepregger, vacuum bag and autoclave method. Mode-I fracture toughness testing revealed a 290% increase in GIc by incorporation of the reactive sizing on the fibers and 10 phr SBM in the matrix. Scanning electron microscopy of the SBM modified CFRP fracture surfaces showed that well distributed, sub 100 nm spherical micelles of SBM underwent cavitation and induced void growth and shear yielding toughening mechanisms to absorb fracture energy. It is noteworthy that longitudinal and transverse composite three point flexural testing showed that the SBM modified matrix did not decrease CFRP strength and stiffness up to 10 phr additive. Further, dynamic mechanical analysis revealed that SBM at 10 phr decreased the glass transition temperature (Tg) of CFRPs by only 2.9 °C; the Tg was then recovered at 15 phr SBM. Finally, the SBM modified CFRP GIc was compared to the neat matrix GIc at 0, 5, 10 and 15 phr SBM to develop a ‘transfer factor’ for SBM modified composites. It was found that only 10% of the increased matrix toughness was transferred from the SBM modified epoxy to the CFRPs. The presence of the rigid carbon fibers constrains plastic deformation of the modified epoxy and limits the toughness transfer in the composite.

    AB - This work explored the incorporation of a triblock copolymer in carbon fiber reinforced epoxy polymer composites (CFRPs) to improve their mode-I fracture toughness, GIc (J/m2). The triblock copolymer poly (styrene)-block-poly (butadiene)-block-poly (methylmethacrylate) (SBM) was used to modify the CFRP matrix at 5, 10 and 15 phr concentrations, respectively. CFRPs were manufactured using an in-house sizing tower system, prepregger, vacuum bag and autoclave method. Mode-I fracture toughness testing revealed a 290% increase in GIc by incorporation of the reactive sizing on the fibers and 10 phr SBM in the matrix. Scanning electron microscopy of the SBM modified CFRP fracture surfaces showed that well distributed, sub 100 nm spherical micelles of SBM underwent cavitation and induced void growth and shear yielding toughening mechanisms to absorb fracture energy. It is noteworthy that longitudinal and transverse composite three point flexural testing showed that the SBM modified matrix did not decrease CFRP strength and stiffness up to 10 phr additive. Further, dynamic mechanical analysis revealed that SBM at 10 phr decreased the glass transition temperature (Tg) of CFRPs by only 2.9 °C; the Tg was then recovered at 15 phr SBM. Finally, the SBM modified CFRP GIc was compared to the neat matrix GIc at 0, 5, 10 and 15 phr SBM to develop a ‘transfer factor’ for SBM modified composites. It was found that only 10% of the increased matrix toughness was transferred from the SBM modified epoxy to the CFRPs. The presence of the rigid carbon fibers constrains plastic deformation of the modified epoxy and limits the toughness transfer in the composite.

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