Thermal field in automated fiber placement of thermoplastic composites: novel experimental contact sensing and conjugate multi-physics numerical modeling

The thermal field around the deposition region during Automated Fiber Placement (AFP) of thermoplastic composites (TPCs) critically governs the quality of the final part. In this work, a new experimental technique is introduced to capture the internal temperature of the incoming tape throughout its entire trajectory, covering regions of the tape before, at, and after the nip point. Engineered sensor tapes are fabricated to replicate the geometry and properties of the actual composite tape, with an embedded fast-response fine thermocouple, allowing direct feeding of the sensor tape into the AFP head during operation. This method enables direct temperature measurements within critical regions previously inaccessible to infrared thermography and impractical for conventional thermocouple placement. Subsequently, a high-fidelity three-dimensional conjugate heat transfer model is developed using the finite volume method to simulate the thermal field during hot gas torch (HGT)-assisted AFP. After validation against the experimental data, a computationally efficient data-driven surrogate, based on multivariate third-order polynomial regression, is trained on simulation results to yield closed-form predictive equations for rapid calculation of critical thermal responses (e.g., nip point temperature, maximum temperature, and immediate cooling rate) from primary input process parameters.