Hygrothermal aging mechanism of carbon fiber/epoxy resin composites based on quantitative characterization of interface structure

The in-situ quantitative characterization of the interface structure and properties of carbon fiber/epoxy resin composites was carried out by using peak force quantitative nanomechanical mapping (PF-QNM) technology in this study. The mechanism of hygrothermal damage was developed. It is found that the hygrothermal aging can be divided into three stages. In the first stage, the resin matrix and the interface absorb simultaneously moisture and the interface size increases linearly from 45.2 +/- 4.1 nm to 76.2 +/- 10.3 nm. The increase of the soft interface area makes the bending strength and interlaminar shear strength decrease by 17.3% and 15.8%, respectively. In the second stage, resin matrix undergoes secondary curing and the interface size continues to increase up to 110.8 +/- 13.8 nm, resulting in the increase of the bending strength, interlaminar shear strength and impact resistance. The impact peak load and strain energy increase by 56.1% and 1286.3%, respectively. In the third stage, interface area is saturated with moisture and the size changes little and the resin continues to absorb moisture, resulting in the swells and plasticization under high temperature and high humidity. The bending strength and interlaminar shear strength of the material decrease respectively to 1185.9 +/- 13.1 MPa and 53.2 +/- 3.2 MPa, with a reduction of 27.6% and 28.0%.

Automated summary

The study used PF-QNM technology to quantitatively characterize the interface structure and properties of carbon fiber/epoxy resin composites in situ, finding that the hygrothermal aging process can be divided into three stages, with different changes in interface size and properties at each stage.