Investigation of the interphase structures and properties of carbon fiber reinforced polymer composites exposed to hydrothermal treatments using peak force quantitative nanomechanics technique

In order to understand the role of interphase in polymer‐matrix composites, a Peak Force Quantitative Nanomechanics technique based on atomic force microscopy was applied to explore the structures and mechanical properties of the interphase region in carbon fiber reinforced poly(ether‐ether‐ketone) (T300/PEEK) and carbon fiber reinforced epoxy (T700/epoxy) composites. The quantitative topographies and elastic modulus maps of each phase of the composites were acquired after 4, 8, 12, 18, and 24 h of hydrothermal ageing. The interphase thickness of T300/PEEK increased from 68.1 ± 10.9 to 76.9 ± 17.0 nm after 8 h of degradation and kept stable at 78.2 ± 18.6 nm, while that of T700/epoxy increased from 45.2 ± 4.1 to 110.8 ± 13.8 nm in the first 8 h and remain stable until 24 h of degradation. Moreover, the moduli of PEEK matrix and epoxy matrix presented a steady and continuous decrease, respectively, during the hydrothermal ageing process and the enlargement of interphase thickness can be attributed to the plasticizing and hydrolytic effects. POLYM. COMPOS., 39:E791–E796, 2018. © 2016 Society of Plastics Engineers