Abstract
Composite materials in practical use can be subjected to a wide variety of different loading conditions. The most important conditions are mechanical stresses and environmental attacks. An issue of major concern in the utilization of composites is associated with the occurrence of delaminations or interlaminar cracks, which may be related to manufacturing defects or are induced in service by low-velocity impacts. The main environmental attacks are temperature, humidity, radiation, and chemical exposure. Three materials were investigated; two thermosetting matrices (unmodified and toughness-modified epoxy, EP and EPmod) and one thermoplastic matrix (semicrystalline polyetheretherketone, PEEK), all reinforced with unidirectional continuous carbon fibres. Samples of these materials were exposed to water in baths of different temperatures; they were taken for mechanical testing after various time periods. As a result of absorbed moisture, GIC-values increased with moisture content of the samples, whereas GIIC-values decreased. By means of scanning electron microscopy, fracture surfaces were examined. Evidence was found that the increase of GIC-values was due to a greater ductility of the matrix (as a result of the moisture absorbed) and hence more energy-consumptive fibre-bridging. On the other hand, interface failure, as well as a loss of shear strength of the epoxy with increasing amount of moisture absorbed, were responsible for the decrease in the GIIC-values. The thermoplastic matrix system (CF/PEEK) exhibited no influence of moisture on the Mode I property, but a decrease of the values for Mode II.
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Disclaimer: 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.