DON26TZ01-NV002 TITLE: Modeling for Frontal Polymerization Curing Process

COMPONENT TECHNOLOGY PRIORITY AREA(S): Advanced Materials

PROJECTED CMMC LEVEL REQUIREMENT: Level 2 (Self)

OBJECTIVE: Develop a multiphysics model or toolset to predict frontal polymerization phenomena and to optimize the resin additives (e,g., catalyst, inhibitor, etc.) for an optimized cure with less distortion or residual stress, while ensuring that the front does not self-extinguish.

DESCRIPTION: Frontal polymerization is the process of curing a resin monomer into a polymer with a localized self-sustaining and moving reaction zone. Frontal polymerization has many benefits over traditional resin cure methods, such as reduced cure time from many hours to seconds or minutes [Refs 1,-2], a significant reduction of the energy required to cure (in some cases over 99.5%) [Ref 3], and reduced cost associated with curing a resin [Ref 3].

Frontal polymerization has many potential applications such as increasing cure percentage for thermoset additive manufacturing processes without requiring a post cure, rapid manufacturing of composite structures, and rapid composite curing for accelerated repairs of composite structures.

Frontal polymerization is a very boundary condition dependent process. Changes in boundary conditions, initial conditions (including temperature and initiation methods), resin formulations, resin or composite thickness, as well as the addition of reinforced fibers or materials can drastically affect characteristics like front velocity, front temperature, and whether a front is sustained or terminated. This can make it challenging to predict and synthesize resin systems that can sustain a frontally polymerized cure with different initiation methods, environmental conditions, composite/resin thicknesses, and reinforcement materials.

Currently, phenomenological multiphysics modeling efforts for frontal polymerization are limited to 1D, 2D, or small 3D models, since they are very computationally demanding due to the highly nonlinear coupling of the governing equations and short timescales required for accurate solution convergence. Furthermore, many models do not predict the mechanical response resulting from the frontal polymerization process (i.e., warpage or residual stress of the polymer caused by the frontal polymerization process). Surrogate modeling can drastically reduce the time to simulate a front but often requires training to create the surrogate model in the form of many finite element analyses or experiments that can be very time consuming. Recently a mechanism-based approach has been created, allowing for prediction of frontal polymerization phenomena without requiring differential scanning calorimetry (DSC) testing to obtain properties for different resin formulations [Ref 4].

This STTR topic calls for development of a model or toolset to predict characteristics of the frontal polymerization process such as front temperature, front velocity, and cure percentage, as well as the resulting effects from the frontal polymerization process such as warpage, residual stress, or post cure mechanical strength. The model should work for multiple initiation methods (i.e., a point initiation of the front, line initiation, and planar initiation for the front (for simulating a point heat source, a line/wire heat source, and a planar heat source). The model should also be scalable, allowing for simulation of different/larger geometries without detrimental increases in computational time. This topic falls under the NAWCAD STTR focus area for in situ material detection and repair solutions.

PHASE I: Develop the framework for a model and determine if the model can predict a frontal cure of a resin with at least one experimentally cured front of a resin as the starting foundation for validation of the model. The model should predict characteristics such as cure percentage, thermal gradients, and front velocity.

The Phase I effort will include prototype plans to be developed under Phase II.

PHASE II: Use a model or framework to optimize additive concentrations (e,g,, catalyst wt%, inhibitor wt%, etc.) to reduce distortion, front temperature, or residual stress for a frontally cured polymer, while ensuring that the front is sustained leading to a fully cured polymer. Use a model or have a framework for simulating or predicting the curing of a fiber reinforced resin. Optimize the additive concentration percentages to reduce distortion of a frontally cured composite patch or panel, while maximizing the percent fiber volume fraction, and ensuring a sustained front/cure. Experimentally validate the model via frontally cured resin and frontally cured composite samples. Optimize the frontal polymerization process for a successful composite cure for different boundary or initial conditions (i.e. ambient temperatures, thicknesses of composite, initiation methods, etc.).

PHASE III DUAL USE APPLICATIONS: Fully develop the model and transition the model and frontal polymerization technology targeting repair applications for NAVAIR. Create representative panels and/or repair patches that meet specifications required for Navy adoption of the technology.

This technology could benefit the private sector by reducing time and cost associated with curing composite structures or performing composite repairs. This could lead to a reduced cost for cured composite structures. Potential secondary applications include reduced cost automotive composite manufacturing, marine/boat composite manufacturing, and renewable energy composite manufacturing.

REFERENCES:

1. Wang, Y. and Lampkin, S. "Rapid Curing of Epoxy Resin Using Self-Sustained Frontal Polymerization Towards the Additive Manufacturing of Thermoset Fiber Composites." Zhupanska, O. and Madenci, E. (Eds.). Proceedings of the American Society for Composites - 37th Technical Conference, ASC 2022. DEStech Publications Inc. https://www.dpi-proceedings.com/index.php/asc37/article/view/36414
2. Tarafdar, Amirreza; Lin, Wenhua; Naderi, Ali; Wang, Xinlu, Fu, Kun (Kelvin; Hosein, Ian D. and Wang, Yeqing. "UV-induced frontal polymerization for optimized in-situ curing of epoxy resin for excellent tensile and flexural properties." Composites Communications, Volume 46, 2024, 101832, ISSN 2452-2139. https://doi.org/10.1016/j.coco.2024.101832 (https://www.sciencedirect.com/science/article/pii/S2452213924000238)
3. Staal, Jeroen; Caglar, Baris and Michaud, Véronique. "Self-catalysed frontal polymerisation enables fast and low-energy processing of fibre reinforced polymer composites." Composites Science and Technology, Volume 251, 2024, 110584, ISSN 0266-3538. https://doi.org/10.1016/j.compscitech.2024.110584 (https://www.sciencedirect.com/science/article/pii/S0266353824001544)
4. Bistri, Donald; Arretche, Ignacio; Lessard, Jacob J.; Zakoworotny, Michael; Vyas, Sagar; Rongy, Laurence; Gómez-Bombarelli, Rafael; Moore, Jeffrey S. and Geubelle, Philippe. "A Mechanism-Based Reaction–Diffusion Model for Accelerated Discovery of Thermoset Resins Frontally Polymerized by Olefin Metathesis." Journal of the American Chemical Society 2024, 146 (31), pp. 21877-21888. DOI: 10.1021/jacs.4c06527

KEYWORDS: Frontal Polymerization; Finite Element Analysis; Composites; Rapid Manufacturing; Rapid Repair; Multiphysics Modeling; Polymerization

TPOC 1
Joshua Piccoli
(301) 757-3194
joshua.piccoli@navy.mil

TPOC 2
Ian Guay
(301) 221-3054
ian.f.guay.civ@us.navy.mil