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Residual stress build-up in thermoset films cured below their ultimate glass transition temperature
KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering, Lightweight Structures.
1997 (English)In: Polymer, ISSN 00323861 (ISSN), Vol. 38, no 4, 809-815 p.Article in journal (Refereed) Published
Abstract [en]

The stress build-up during isothermal cure below the ultimate glass transition temperature of epoxy and acrylate films is investigated in detail. Four systems are studied; two acrylates and two epoxies, with different crosslink densities. Relaxation modulus and film shrinkage are measured simultaneously during cure. The stress build-up is measured independently using a bi-layer beam bending technique. A model for the build-up of cure stresses is proposed, in which stresses are generated by the cure shrinkage and decay by viscoelastic relaxation. The relaxation is described by a simple, modified Maxwell model. Owing to the absence of memory in the Maxwell model, the resulting equation is simple and numerical stress computation straight-forward. The stress build-up over time is thus simulated for the four model systems based on the relaxation and shrinkage data, and the simulations compared with the experimentally observed stress build-up. The model successfully predicts the cure stresses where more standard elastic methods fail. It is found that the amount of stress build-up during cure varies greatly between the different systems. In general, a higher crosslink density results in higher stress build-up. The stress on cure ranged from less than 1% of the total stress on cure and cool-down in a lightly crosslinked epoxy to more than 30% of the total stress in densely crosslinked epoxies and acrylates. Finally simple approximations for estimating the stress levels after cure and cool-down from basic material properties, e.g. modulus and cure shrinkage, are proposed. © 1997 Elsevier Science Ltd. All rights reserved.

Place, publisher, year, edition, pages
1997. Vol. 38, no 4, 809-815 p.
Keyword [en]
Residual stress, Thermoset cure, Viscoelastic modelling, Crosslinking, Curing, Epoxy resins, Glass transition, Mathematical models, Polyacrylates, Residual stresses, Thermosets, Film shrinkage, Glass transition temperature, Relaxation model, Stress build-up, Thermoset films, Plastic films
National Category
Applied Mechanics
URN: urn:nbn:se:kth:diva-80049OAI: diva2:495985

References: Croll, S.G., (1979) J. Coat. Technol., 51, p. 49; Siegmann, A., Buchman, A., Kenig, S., (1981) Polym. Eng. Sci., 21, p. 997; Sato, K., (1980) Prog. Org. Coat., 8, p. 143; Lange, J., Toll, S., Hult, A., MÃ¥nson, J.-A.E., (1995) Polymer, 36, p. 3135; Lange, J., Hult, A., MÃ¥nson, J.-A.E., Polymer, , in press; Martin, J.E., Adolf, D., (1990) Macromolecules, 23, p. 5014; White, S.R., Hahn, H.T., (1992) J. Compos. Mater., 26, p. 2402; Bogetti, T.A., Gillespie J.W., Jr., (1992) J. Compos. Mater., 26, p. 626; Ochi, M., Yamashita, K., Shimbo, M., (1991) J. Appl. Polym. Sci., 43, p. 2013; Dannenberg, H., (1965) SPE Journal, p. 669; Alperstein, D., Narkis, M., Siegman, A., Binder, B., (1995) Polym. Eng. Sci., 35, p. 754

NR 20140805Available from: 2012-02-09 Created: 2012-02-09 Last updated: 2014-04-08Bibliographically approved

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