To improve the mechanical properties of carbon fiber reinforced polymer (CFRP) bonding interface, the surface treatment of CFRP was performed using low-temperature oxygen plasma treatment equipment. The surface physico-chemical properties including surface wettability, surface energy, surface morphology and surface chemical components of CFRP were characterized by contact angle measurement, scanning electron microscopy (SEM), atomic force microscopy (AFM) and X-ray photoelectron spectroscopy (XPS) test equipment, as well as the mechanical properties of CFRP bonding interface was tested by double cantilever beam (DCB) test. The results show that the water contact angle of surface decreases from 97° to 29° with the increase of oxygen plasma treatment time from 0 s to 30 s, as well as the surface wettability of CFRP is the best and the percentage of polar components increases significantly. As the increase of treatment time, the surface roughness and the maximum height difference of CFRP decrease significantly, and more nanoscale grooves with valley distribution are formed and thus the surface area of substrate increases. Meanwhile, the content of oxygen-containing polar functional groups including C—O and C＝O on the surface are increased obviously, the content of C—C/C—H and Si—C functional groups are decreased, and the surface contaminants are effectively removed or transformed. In comparison with the untreated specimens, the maximum peeling load and mode Ⅰ fracture toughness of CFRP adhesive interface are improved by 1.01 times (62.73 N) and 1.92 times (649.21 J/m2) after oxygen plasma treatment for 20 s, respectively. The study reveals that oxygen plasma treatment can significantly improve the physico-chemical properties of CFRP surface, which is conducive to better bonding between CFRP and adhesive, and improve the peel strength and toughness of the adhesive interface.
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