Creep Age Forming of Fiber Metal Laminates: Effects of Process Time and Temperature and Stacking Sequence of Core Material

Fiber metal laminates (FMLs) are a type of hybrid materials interlacing composites and metals. In the present work, FMLs with aluminum alloy 6061 as the skin and E-glass fiber-reinforced polypropylene (PP) as the core material are fabricated and formed by the creep age forming (CAF) process. The effects of time and temperature as the process parameters and thickness and stacking sequences of composites layers as the FML parameters are evaluated on the springback of glass-reinforced aluminum laminates (GLARE) FMLs. After the CAF process, the springback of creep age-formed FMLs is calculated. The results show that the FMLs can be successfully formed with the CAF process by considering appropriate time and temperature. In addition, the stacking sequence of composite layers can affect the springback behavior of FMLs significantly.

Experimental investigation, statistical modeling and multi-objective optimization of creep age forming of fiber metal laminates

The experimental assessment of the creep age forming performance of fiber metal laminates was considered in this study. To this end, different fiber metal laminates with the stacking sequence of [Al/02/Al] were manufactured using aluminum alloy 6061 sheets as skins along with E-glass fiber-reinforced polypropylene and E-glass fiber-reinforced polyamide 6 as two different cores. Next, a comprehensive investigation was conducted on the impacts of two main parameters in the creep forming process, i.e. the effect of time and temperature on the spring-back properties of deformed fiber metal laminates. Initially, using the design of experiments and based on the response surface methodology, an imposed spring-back of the creep age formed fiber metal laminates was modeled and the governing linear regression equations were derived and verified. Then, to find the best combination yielding the minimum spring-back, the process inputs (time and temperature) were optimized. The results proved that with an increase in either time or temperature, the spring-backs of the two types of creep age formed fiber metal laminates decreased due to the decrease in elastic strains and the increase of creep strains. Also, to achieve a creep age formed fiber metal laminate with minimum spring-back according to multi-objective optimization in both fiber metal laminates, the most proper values of time and temperature should be taken as 6 h and approximately 160°C, respectively.