The composite tow placement process is a non-autoclave consolidation method that involves in situ consolidation and bonding of thermoplastic tape on a preconsolidated substrate. It can be used as a method for manufacturing large composite structures with a high degree of process control and dimensional accuracy. The bond strength that develops between layers within the laminate ultimately governs the final strength of the part. In this work, a model is presented for predicting through-thickness heat transfer and bond strength development based on intimate contact and healing at the ply interface. Experiments are carried out to validate these results for a wide variety of process conditions, and they show that model based predictive control can be used as a method for process optimization. The numerical results show that bond strength development is significantly affected by the process set points (e.g., head velocity heat input and roller pressures), and that the resulting strength can vary significantly within the part based on these set points.
Thermoplastic composite tow-placement technology is a nonautoclave consolidation process that offers the potential to significantly reduce fabrication costs by using in situ consolidation as a method for manufacturing large composite components. The temperature history and resulting degree of consolidation directly control the final part quality and are directly affected by the process set points. In this work, series of integrated submodels are developed for predicting the heat transfer and void dynamics within the laminate. The final through thickness void fraction is predicted as a function of process parameters. Experiments are carried out to validate these results for a wide variety of process conditions. The model is used to quantify the relationships between variation of quality of incoming material (e.g., void content ranges 3.1 and 5.5% and final void content gradients. It was found that significant gradients in final void content exist through the thickness and is directly related to processing conditions. Recommendations for process optimization are discussed.
This paper focuses on the contact between layers in forming processes of composite laminate. The link between the degree of intimate contact and the consequent thermal contact resistance between layers is investigated. A hot plate forming process experiment allows to propose a relation and determine the missing parameter for APC2 thermoplastic prepreg composite. Beside the new proposed relation, this work showed that the internal thermal contact resistances in the laminate is significant. Therefore, thermal modeling of forming processes of composite laminate (such as automatic tape placement) should account for this phenomenon.
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