Abstract
ABSTRACT We conducted an in situ study on CFRP fracturing process using atomic-force-microscopy-based stress-sensitive indentation. Tensile stress distribution during fracture initiation and propagation was directly observed quantitatively. It led to a discovery that previously believed catastrophic fracture of individual carbon fiber develops in a controllable manner in the polymer matrix, exhibiting 10 times increase of fracture toughness. Plastic deformation in crack-bridging polymer matrix was accounted for the toughening mechanism. The model was applied to explain low temperature strength weakening of CFRP bulk material when matrix plasticity was intentionally ‘shut down’ by cryogenic cooling.
Highlights
The high stiffness and high strength per body weight offered by carbon fiber reinforced polymer (CFRP) has gained ever increasing applications for this structural composite in areas of astronautics, aviation, automobiles, ships, infrastructure constructions, sports goods, etc
It was reported in several atomic force microscopy (AFM) indentation studies that the measured value of E is affected by the presence of in-plane tensile stress [28,29,30]
The up-left panel shows an unstressed CFRP with CF modulus averaged around 44 GPa and P modulus averaged around 8 GPa
Summary
The high stiffness and high strength per body weight offered by carbon fiber reinforced polymer (CFRP) has gained ever increasing applications for this structural composite in areas of astronautics, aviation, automobiles, ships, infrastructure constructions, sports goods, etc. While a simple law of mixture can explain the high stiffness of CFRP coming from the high stiffness of carbon fiber with analogy to springs in parallel, the mechanism for the composite high strength is not trivial [2]. Though individual carbon fiber has a high strength, Griffith discovered 100 years ago that small fiber of brittle material is stronger than its bulk counterpart only because of the lower chance to develop a critical fracture-initiating defect [3]. CFRP exhibits fracture toughness almost twice that of both constituents: the strong but brittle carbon fiber (CF) and the ductile but weak polymer (P) matrix, breaking the law of mixture [5,6,7]
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
