Session: 03-08-01: Integrated Computational Materials Engineering

Paper Number: 189379

189379 - Numerical Simulation of Thermal Behavior and Crystallization Development During Automated Fiber Placement of a Thermoplastic Composite Plate 

Numerical simulation of thermal behavior and crystallization development during automated fiber placement of a thermoplastic composite plate

Ali Koohi Esfahani¹ , Mehran Tehrani^1,2, and Jiun-Shyan Chen¹

¹ Department of Structural Engineering, University of California San Diego, La Jolla, CA 92093

² Program in Materials Science and Engineering, University of California San Diego, La Jolla, CA 92093

This study develops an evolving adaptive finite element (EA-FEM) model coupled with kinetics of crystallization to predict thermal behavior and crystallization development during the in-situ consolidation automated fiber placement (AFP) of a thermoplastic composite plate. The model accurately captures the complex thermal behavior during consolidation and the heat equation is coupled with the crystallization kinetics of the thermoplastic matrix. The crystallization kinetics is governed by the Velisaris–Seferis model which assumes primary and secondary crystallization as independent phenomena. Due to the continuous nature of the AFP process, crystallization develops under continuous cooling whereas the Avrami formulation used for both primary and secondary crystallization in the Velisaris model is valid only under isothermal conditions. In order to predict crystallization behavior under non-isothermal conditions, Scheil’s additivity rule combined with pseudo times is utilized. Based on the additivity rule, cooling histories are discretized into small time intervals and within each time step, the temperature is assumed to be constant. The additivity fraction is evaluated by accumulating the ratio of each time increment to the corresponding temperature-dependent incubation time. The onset of crystallization is then assumed to occur when the additivity fraction reaches unity. Reliable prediction of thermal and crystallization behavior in AFP requires accurate modeling of the underlying transient thermal field as well as heat transfer across interlaminar interfaces. Accordingly, EA-FEM constructs domain elements in accordance with the actual material deposition process and path. The developed approach avoids the use of the conventional fixed-discretization with scaling approach by adaptively updating the finite element discretization, minimizing numerical errors and avoiding ill-conditioning commonly observed in the conventional methods. The implemented adaptive method yields computational gain over conventional methods as only the active nodal degrees of freedom are considered at a time resulting into smaller algebraic systems Furthermore, since the layer-to-layer interfaces in AFP are not perfectly bonded during deposition and exhibit thermal resistance, assuming ideal interlaminar conduction leads to inaccurate heat-transfer predictions. To account for this effect, gap elements are introduced between adjacent deposited layers to explicitly represent interlaminar thermal resistance. The developed model was validated against results reported in the literature, demonstrating good agreement under similar AFP processing conditions. The resulting framework provides an accurate and robust tool for large-scale AFP simulations, enabling reliable predictions of thermal behavior, interlaminar heat-transfer effects, and the evolution of primary and secondary crystallization during the AFP process.

Presenting Author: Ali Koohi Esfahani University of California San Diego

Presenting Author Biography: I am a PhD student at university of California San Diego. My research focuses on numerical simulation of thermal behavior and crystallization development during automated fiber placement of a thermoplastic composite plate.