Session: IMECE Undergraduate Research and Design Exposition

Paper Number: 121109

121109 - The Effect of Process Parameters on Frontal Polymerization-Based Manufacturing of Composites 

Thermoset polymers and carbon-fiber-reinforced polymer composites are widely used throughout various industries due to their desirable material properties. Standard manufacturing techniques for these materials rely on the use of large autoclaves wherein parts are cured using complex curing cycles at high temperature and pressure. Frontal polymerization (FP) is a technique that circumvents these energy inefficient curing cycles by utilizing a self-propagating exothermic reaction front initiated by a small thermal trigger. This reaction front propagates through the thermoset resin, polymerizing the monomer as it passes. The frontally polymerizable monomer considered in this study is dicyclopentadiene (DCPD), chosen for its ability to produce high-strength and high-stiffness carbon-fiber-reinforced polymer composites. In addition to an orders of magnitude reduction in energy input, FP also allows for the free-form additive manufacturing of both polymers and composite tows by direct ink writing (DIW). The ability to efficiently manufacture intricate, high performance polymeric and composite structures without the need for a mold or significant post-processing operations makes FP-based manufacturing a robust alternative to autoclave-based methods. In this work we seek to numerically model the FP-based manufacturing of composites to determine the effect of various process parameters and optimize processing conditions. 

In the FP-DIW system, a pre-impregnated tow is drawn between two heated rollers that initiate and sustain the FP reaction and supply a compaction force for consolidation. We introduce a homogenized thermochemical model for the FP-DIW of composite tows that takes into consideration the drawing speed, roller temperature, and the fiber volume fraction of the tow. It also includes ambient heat loss and thermal contact resistance at the roller-tow interface. An important consideration in implementing this technique is the effect of these process parameters on the location of the front, due to its effect on the consolidation of the tow. Further, the process parameters should be optimized to ensure the final degree of cure and the thermo-mechanical properties of the printed tow are suitable for high performance applications. This model is used to establish the dependence of the front location and degree of cure of the printed composites on the process parameters and is compared with experimental results. Finally, we calculate the predicted energy input for the roller system and compare this to the energy required by conventional composite manufacturing.

We then present a homogenized thermochemical model for the FP manufacturing of DCPD composite laminates, in which layers of unidirectional carbon fibers embedded in DCPD resin are stacked with varying orientations. Composite laminates are frequently used for structural components due to their high stiffness along multiple directions. We study the effect of the fiber orientation angles in angle-ply laminates on the numerically computed front velocity and provide comparisons with analytical predictions based on homogenization theory. Furthermore, we consider the case of woven composites, which consist of unidirectional carbon fiber tows woven together into a fabric. We examine the effect that the fabric structure and the fiber volume fraction have on the front velocity and transient nature of the front propagation and make similar analytical and experimental comparisons.

Presenting Author: Gavin DeBrun University of Illinois Urbana-Champaign

Presenting Author Biography: Gavin DeBrun is a senior at the University of Illinois Urbana-Champaign in the Department of Physics. He is a member of the Geubelle Research Group and the collaborative Autonomous Materials Systems Group at the Beckman Institute for Advanced Study. He is also an intern at Sandia National Laboratories, where he studies corrosion mitigation coatings for spent nuclear fuel canisters. Previously, he has worked with the Rauber Atmospheric Science Group at UIUC to investigate extreme extratropical cyclones and with Sandia National Laboratories' Photovoltaic Systems Evaluation Laboratory to optimize photovoltaic power production. His current work with the Geubelle Group focuses on the modeling of composite materials manufacturing by frontal polymerization.

Authors:

Gavin DeBrun University of Illinois Urbana-Champaign
Michael Zakoworotny University of Illinois Urbana-Champaign
Nadim Hmeidat University of Illinois Urbana-Champaign
Sameh Tawfick University of Illinois Urbana-Champaign
Nancy Sottos University of Illinois Urbana-Champaign
Philippe Geubelle University of Illinois Urbana-Champaign