N23A-T006   TITLE: Microwave Curing Process Modeling for Continuous Carbon Fiber Reinforced Thermoset Composites

OUSD (R&E) CRITICAL TECHNOLOGY AREA(S): General Warfighting Requirements (GWR)

OBJECTIVE: Develop simulation models and visualization tools for microwave curing process of carbon fiber reinforced composites, and demonstrate the feasibility to manufacture high quality carbon fiber reinforced composites using microwave radiation.

DESCRIPTION: Autoclaves are widely utilized to process and manufacture high-performance aircraft composite materials. This conventional method provides laminate consolidation by application of elevated pressures and temperatures; however, the high costs and extensive process times associated with this technique have generated an interest in the implementation of out of autoclave curing methods. Microwave curing is gaining increasing attention as an alternative tool for composite industrialization, due to its potential for reduced cure times, low energy consumption, and mass production.

Microwave systems heat materials via electromagnetic field interaction. Electromagnetic fields are transferred to the material, and heat is generated through polarization. Microwave curing has been used for glass fiber composite processing, but there are significant challenges associated with microwave curing of carbon fiber composites. Efficient heating is difficult due to high dielectric loss and low depth of penetration associated with carbon fibers. Another major challenge is related to arcing of carbon fibers, which can result in very high-localized hot spots that damage the surrounding material. Laminate quality is highly dependent on the uniformity of the electromagnetic field in the material. The anisotropic dielectric properties of composite constituents disrupts the intended homogeneous volumetric cure, resulting in non-uniform heating. This heating behavior requires further investigation; highlighting the need for a tool that can model this phenomenon.

This STTR topic seeks to develop a multi-physics based model that simulates and optimizes the microwave curing process of thick fiber reinforced composites (up to 10 mm). The model should account for the interaction of electromagnetic, thermal, and chemical mechanisms induced during the curing process. The tool will be used to model aerospace-grade thermoset composite materials (such as IM7/8552) of varying lay-up thicknesses and fiber orientations, to predict curing behavior and material properties. The model predictions for microwave cured fiber reinforced composites will be validated by qualitative (such as porosity, defects, etc.), mechanical (such as tension, flexure, impact, etc.) and chemical (such as differential scanning calorimetry, dynamic mechanical analysis, etc.) coupon testing.

The implementation of a microwave curing process would result in reduced cure times and reduced energy consumptions. The modeling tool would aid in the reduction of test runs required for composite part production. It would also give companies greater production scheduling freedom through process modeling of components. This would make production more adaptive and save scheduling time and costs.

PHASE I: Develop a modeling methodology based on the proposed concept of a multi-physics tool that can simulate and optimize the microwave curing process of fiber reinforced composite materials. Demonstrate feasibility of the methodology and investigate the effects of the microwave curing conditions, such as power, duration, composite orientation, composite thickness, etc., via simulations, that account for electromagnetic, thermal, and chemical mechanisms on the mechanical properties of the cured composite. The Phase I effort will include prototype plans to be developed under Phase II.

PHASE II: Develop the proposed multi-physics tool to address microwave manufacturing of fiber reinforced composites of thicknesses up to 10 mm. Demonstrate and validate the tool by comparing simulation predictions to the results of various qualitative, mechanical, and chemical tests of microwaved and autoclaved cured fiber reinforced composite coupons.

PHASE III DUAL USE APPLICATIONS: Enhance and demonstrate this tool with difficult to process parts, associated with autoclave curing, and with different material systems. Coordinate with the prime and sub-contractors producing composite parts to facilitate the transition and utilization of this tool.

The product outcome of this topic has extensive applications for companies producing fiber- reinforced composite parts, in particular companies that utilize an autoclave process. This topic desires to provide a modeling tool to optimize the alternative microwave curing process for the production of quality parts at a lower cost (50% reduction) and quicker turnaround times (40% reduction).

REFERENCES:

1.       Mishra, R. R., & Sharma, A. K. (2016). Microwave�material interaction phenomena: heating mechanisms, challenges and opportunities in material processing. Composites Part A: Applied Science and Manufacturing, 81, 78-97. https://doi.org/10.1016/j.compositesa.2015.10.035

2.       Mgbemena, C. O., Li, D., Lin, M. -F., Liddel, P. D., Katnam, K. B., Thakur, V. K., & Nezhad, H. Y. (2018). Accelerated microwave curing of fibre-reinforced thermoset polymer composites for structural applications: A review of scientific challenges. Composites Part A: Applied Science and Manufacturing, 115, 88-103. https://doi.org/10.1016/j.compositesa.2018.09.012

3.       Galos, J. (2021). Microwave processing of carbon fibre polymer composites: a review. Polymers and Polymer Composites, 29(3), 151-162. https://doi.org/10.1177/0967391120903894

 

KEYWORDS: Microwave curing; Manufacturing process; Physics-based modeling; Carbon fiber thermoset composites; Process optimization; Mechanical testing

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