Strain analysis of a glass-fibre-reinforced polyester under dynamic loads
Strain on fibreglass-reinforced polyester was analysed for different types of stress-strain patterns to determine the existence of a critical point on the respective diagrams. This critical point defines the maximum strain value prior to a steep and abrupt increase that causes failure. «Useful life» should, therefore, be regarded to be the number of cycles associated with the critical point rather than the number associated with failure. The tests conducted in this study showed that the number of critical point cycles was around 95% of the yield point cycles. The degradation rate of the material tested under different loads was found with an analytical model applied to the most common strain pattern. The model proposed also showed that the stress ratio, R, was related to elastic modulus degradation. When studied for load state values of 10 to 16% of the ultimate tensile strength (UTS), material life expectancy was found to be 104 to 107 cycles. No fatigue limit appeared for these values, however. Immersion of the material in water and subsequent drying under ambient conditions was found not affecting either deformation or deformation-related variables. Finally, a model was developed to predict life expectancy from the maximum strain values.
Andersen S.L., Lilhot H., 1988. Fatigue of glass/polyester composite materials for wingblades. European Community Wind Energy Conference, Herning, Denmark, 6-10 June, pp. 324-346.
Anderson, 1996. Properties of composites with long fibres. In: Design of composite structures against fatigue (Mayer R.M., ed). John Wiley and Sons Ltd, Denmark.
Bach P.W., 1988. High cycle fatigue investigation on windturbine materials. Proceedings of European Community Wind Energy Conference, Herning, Denmark, 6-10 June, pp. 337-341.
Bach P.W., 1991. High cycle fatigue testing of glass fibre reinforced polyester and welded structural details. Report ECN-C-91-010. Netherlands Research Energy Foundation, Petten, The Netherlands.
Bach P.W., 1992. Fatigue properties and design of wing blades for windturbines. Joule Project, Progress Report. pp. 250-251.
Bach P.W., 1993. The effect of moisture of the fatigue performance of glass fibre reinforced polyester coupons and bolted joints. European Community Wind Energy Conference, Lübeck-Travemünde, Germany. pp. 180-183.
Bach P.W., 1994. Fatigue lifetime of glass polyester laminates for wind turbine blades. Report ECN-C-94-020. Netherlands Research Energy Foundation, Petten, The Netherlands.
Bach P.W., 1996. The effect of moisture of the fatigue performance of glass fibre reinforced polyester coupons and bolted joints. Report ECN-C-96-015. Netherlands Research Energy Foundation, Petten, The Netherlands.
Boller K.H., 1969. Fatigue fundamentals for composite materials. American Society for Testing and Materials. American Society of Testing and Materials, STP 460. pp 217-235.
Gerharz J.J., Schütz D., 1980. Literature research on the mechanical properties of fibre composite materials. Analysis of the state of the art. Royal Aircraft Establishment. Library Report. Translation 2045. Vol. 1, pp. 29-30.
Gitschner H.W., Menges G., 1979. Sorption, swelling and creep behaviour of glass fibre reinforced composite materials. Conference: Recent advances in the properties and applications of thermosetting materials. Plastic & Rubber Institute. 5-6 Dec. Coventry. pp. 15.1-15.8.
Greenwood J., 1981. The long term stress rupture, creep and fatigue properties of glass reinforced polyester and epoxide resin: introduction to the literature survey. ERA report No. 81-120R. Project No. 71/01/3713.
Hull D., 1987. Materiales compuestos. Ed Reverté, Barcelona. [In Spanish].
Hwangw., Han K.S., 1986. Fatigue of composite-fatigue modulus concept and life prediction. J Composite Material 24, 125-165.
Mandell J.F., 1982. Development in reinforced plastics. Vol 2 (Pritchard O., ed). Applied Science Publishers, London. 67 pp.
O'Brien T.K., 1985. Analysis of local delaminations and their influence on composite laminate behaviour. American Society for Testing and Materials.
Oller S., 2002. Análisis y cálculo de estructuras de materiales compuestos. Universidad Politécnica de Cataluña, Barcelona. [In Spanish]. PMCid:1241257
Paris P.M., Gómez M., Andersonw., 1961. A rational analytic theory of fatigue. The Trend in Engineering 13, 9-14.
Reifsnider K.L., 1991. Fatigue of composite materials. Elsevier, Amsterdam.
Scola D.A., 1975. A study to determine the mechanisms of S-glass/epoxy resin composite degradation due to moist and solvent environment. Proc Annual Conference –Reinforced Plastics/Composites Institute, Society of the Plastics Industry, NY, 30, 19.
Talreja R., 1986. Fatigue of composite materials. Technomic Publ. Inc, Lancaster, PA, USA.
Talreja R., 1997. A damage mechanics based approach to durability assessment of composite material. In: Composites and functionally graded materials, MD-Vol 80. American Society of Mechanical Engineers. pp. 151-156.
Vázquez J., Silvera A., Arias F., Soria E., 1998. Fatigue properties of a glass-fibre-reinforced polyester material used in wind turbine blades. J Strain Anal Eng 33(3), 183-193. http://dx.doi.org/10.1243/0309324981512904
Wang C.S., Wang A.S., 1980. Creep behaviour of glassepoxy composite laminates under hygrothermal conditions. In: Advances in composite materials (Bunsell et al., ed). Vol. 1. Pergamon Press, Paris. pp. 569-578
Watanabe M., 1979. Effect of water environment on fatigue behaviour of fibre reinforced plastic . Proc 5th Conference on Composite Materials, Testing and Design, ASTM STP 674, Philadelphia, PA, USA. pp. 345-367.
Yang J., Du S., 1983. An exploratory study into the fatigue of composites under spectrum loading. J Comp Mater 17, 511-526.
© CSIC. Manuscripts published are the property of Consejo Superior de Investigaciones Científicas, and quoting this source is a requirement for any partial or full reproduction.
SJAR is an Open Access Journal. All articles are distributed under the terms of the Creative Commons Attribution 4.0 International (CC BY 4.0) License. You may read here the basic information and the legal text of the license. The indication of the license CC-by must be expressly stated in this way when necessary.