The effect of thermal and cryogenic environments on the impact performance of aluminum-glass fibers/epoxy laminated composites

In this research work, the effect of various environments on the impact properties of fiber metal laminates was investigated. To do so, in the first step, the 2024 aluminum layers were surface modified with the etching method. Then, the various glass fibers/epoxy composites with the configurations of (0 degrees/0 degrees/0 degrees/0 degrees, 90 degrees/90 degrees/90 degrees/90 degrees, +45 degrees/-45 degrees/-45 degrees/+45 degrees and 0 degrees/90 degrees/90 degrees/0 degrees) were sandwiched between two aluminum sheets. In the following, these samples were aged under thermal cycling (between 25 and 100 degrees C), isothermal aging at the temperature of 100 degrees C, cryogenic cycling (between -196 and 25 degrees C), and cryogenic isothermal aging at the temperature of -196 degrees C. To understand the effect of various aging methods on the mechanical features of these structures, the Charpy impact test was performed. Also, the failure mechanisms and related phenomena were assessed by visual observations and microstructural investigations. In the first steps of thermal aging, the impact strength of FMLs was improved, which the highest of that being 46.9%. In the higher cycles or exposing times, the impact strength showed reducing trends, due to thermal degradations of the epoxy matrix. The cryogenic cycling in the high cycles reduced the impact strength of FMLs. But in the cryogenic isothermal condition, in some cases, the improvement in the impact strength was seen, which the highest of that being about 43.4%.

Automated summary

This research investigated the effect of various environments on the impact properties of fiber metal laminates. Surface modification of 2024 aluminum layers was done using the etching method. Different configurations of glass fibers/epoxy composites were sandwiched between two aluminum sheets. Thermal cycling, isothermal aging, cryogenic cycling, and cryogenic isothermal aging were used as aging methods. Charpy impact tests, visual observations, and microstructural investigations were conducted to assess the mechanical features and failure mechanisms.