Residual Stress Prediction of a Thermoformed Carbon Fiber Reinforced Polymer Structure Through a Novel Manufacturing to Response Pathway
2022-01-0321
03/29/2022
- Event
- Content
- Thermoforming of thermoplastic-based continuous carbon fiber reinforced polymer (CFRP) offers major advantage in reducing cycle times for large scale productions, but it inevitably induces certain undesirable effects in the formed parts. One such effect is residual stress. For a complex CFRP structure, the magnitude and state (tension/compression) of the residual stress could vary at different locations on the part. Several researchers have developed a number of techniques to experimentally measure the magnitude of these residual stresses, which have shown that these residual stresses could have considerable impact on the mechanical performance of complex CFRP structures, especially developed using thick laminates. However, the degree of impact of the residual stresses on the structural performance of the part still represents a knowledge gap. Experimental investigations could be performed to study the impact of residual stresses on mechanical performance but they are tedious and time-consuming. Instead, a numerical modeling route could be adopted. This route consists of performing manufacturing simulations followed by residual stress analysis using a finite element (FE) method. The predicted residual stresses could then be mapped on the FE model which can be analyzed for mechanical performance through a mechanical simulation. Essentially, an end-to-end analysis pathway would be required to comprehensively study process effects on mechanical performance. Such a pathway would be efficient, provided accurate prediction of residual stresses is possible with a numerical procedure. In order to ensure accuracy of the numerical procedure, the predicted stresses need to be compared with the stresses measured experimentally. The current study focusses on accurately predicting the residual stresses by implementing the aforementioned numerical pathway. A thermoplastic based CFRP hat structure was thermoformed and the residual stresses in the formed structure were measured using Hole Drilling and DIC techniques. On the numerical side, thermoforming simulation was performed to closely capture the details of the experimental setup. Further, cooling analysis was performed, and the residual stress determination procedure was implemented. This procedure was based on the incremental classical laminate theory. The stress results from numerical method and experiments were compared. A good agreement between the simulated and measured results indicated that the numerical pathway can be used to study the impact of the residual stresses on the mechanical performance.
- Citation
- Limaye, M., Pradeep, S., Kothari, A., Agha, A. et al., "Residual Stress Prediction of a Thermoformed Carbon Fiber Reinforced Polymer Structure Through a Novel Manufacturing to Response Pathway," SAE Technical Paper 2022-01-0321, 2022, .