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Manufacturing Induced Residual Stress Development and Deformation in PMDI-10 Structural Foam

Rao, Rekha R.; Long, Kevin N.; Roberts, Christine C.; Soehnel, Melissa M.; Johnson, Kyle J.

In this report, we investigate how manufacturing conditions result in the warpage of moderate density PMDI polyurethane foam (12-50 lb/ft 3 ) when they are released from a mold. We have developed a multiphysics modeling framework to simulate the manufacturing process including resin injection, foaming and mold filling, gelation of the matrix, elevated cure, vitrification, cool down, and demolding. We have implemented this framework within the Sierra Mechanics Finite Element Code Suite. We couple Aria for flow, energy conservation, and foaming/curing kinetics with Adagio for the nonlinear viscoelastic solid response in a multi-staged simulation process flow. We calibrate a model for the PMDI-10S (10 lb/ft 3 free rise foam) through a suite of characterization data presented here to calibrate the solid cure behavior of the foam. The model is then used and compared to a benchmark experiment, the manufacturing and warpage over 1 year of a 10 cm by 10 cm by 2.5 cm foam "staple'. This component features both slender and thick regions that warp considerably differently over time. Qualitative agreement between the model and the experiment is achieved but quantitative accuracy is not. 2

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TYPE SAND Report YEAR 2018
OSTIDOI

The kinetics of polyurethane structural foam formation: Foaming and polymerization

AIChE Journal

Rao, Rekha R.; Mondy, L.A.; Long, Kevin N.; Celina, Mathias C.; Wyatt, Nicholas B.; Roberts, Christine C.; Soehnel, Melissa M.; Brunini, Victor B.

Kinetic models have been developed to understand the manufacturing of polymeric foams, which evolve from low viscosity Newtonian liquids, to bubbly liquids, finally producing solid foam. Closed-form kinetics are formulated and parameterized for PMDI-10, a fast curing polyurethane, including polymerization and foaming. PMDI-10 is chemically blown, where water and isocyanate react to form carbon dioxide. The isocyanate reacts with polyol in a competing reaction, producing polymer. Our approach is unique, although it builds on our previous work and the polymerization literature. This kinetic model follows a simplified mathematical formalism that decouples foaming and curing, including an evolving glass transition temperature to represent vitrification. This approach is based on IR, DSC, and volume evolution data, where we observed that the isocyanate is always in excess and does not affect the kinetics. The kinetics are suitable for implementation into a computational fluid dynamics framework, which will be explored in subsequent articles. © 2017 American Institute of Chemical Engineers AIChE J, 63: 2945–2957, 2017.

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TYPE Journal Article YEAR 2017
ScopusOSTIDOI
Results 26–50 of 111
Results 26–50 of 111