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Effects of Carbon Nanomaterial Reinforcement on Composite Joints Under Cyclic and Impact Loading
NAVAL POSTGRADUATE SCHOOL MONTEREY CA
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This study investigated the influence of Multi-Walled Carbon Nanotubes MWCNTs and Carbon Nanofibers CNFs reinforcement on the behavior of Carbon Fiber Reinforced Polymer CFRP joint interface under cyclic and impact loading. Test coupons with pre-cracks were fabricated via Vacuum Assisted Resin Transfer Molding VARTM technique with 7.5gm2 of MWCNTs or CNFs dispersed at the joint interface ahead of the crack tip. The test coupons were loaded in 3-point bending at 2Hz and 10Hz frequencies for the cyclic loading test. The CNTs and CNFs-reinforced samples displayed higher stiffness and had significantly shorter crack propagation lengths under the same loading cycles. Resistance to crack propagation was evident in the reinforced samples as observed using an optical microscope. Similar sets of reinforced as well as non-reinforced samples were subjected to low energy impact tests and their dynamic responses and failures were also compared. CNTs-reinforcement samples experienced failure at higher impact force as compared to non-reinforced samples. However, further testing was recommended to establish the effects of CNFs reinforcement under impact loading. The test results suggested that proper reinforcement of the joint interface using carbon nanomaterial can significantly delay the crack growth, resulting in improvement of composite structural integrity and its service life.
APPROVED FOR PUBLIC RELEASE