Balancing Mechanisms of Distortion to Yield Distortion-free/Shape Stable Composites

Abstract

The underlying mechanisms of manufacturing distortion in composite components have been suggested to be anisotropy, material property gradients, and part-tool interactions. These mechanisms have been sub-divided into those that result in shape change with changing temperature (thermoelastic) and those that are one-time-only effects (non-thermoelastic), generally related to isothermal cure shrinkage. The responses related to anisotropy and material property gradient mechanisms are predicted to include both thermoelastic and non-thermoelastic contributions; however, stresses imposed on the laminate and the resulting distortion due to part—tool interaction is merely non-thermoelastic in nature. Previous research has suggested that this non-thermoelastic component is critical to generating a composite angle bracket on net-shape tooling that is simultaneously distortion-free and shape-stable with temperature.

The current research investigates the degree of tailorability available in both the part—tool interaction and in the thermoelastic response to local corner asymmetry. Autoclave-cured angle brackets were produced with variations in the local stacking sequence in the corner to balance the thermoelastic contributions and with different mold releases to affect the stress transferred from the tool to the part. Two asymmetric stacking sequences are compared to the baseline symmetric laminate. The fraction of the corner radius that is made up of these regions of asymmetry is also adjusted to vary the thermoelastic effect. Mold release variations are investigated to evaluate the effect of changing levels of non-thermoelastic distortion. To measure the response, the curvatures of flat composite laminates are measured using an LVDT-based panel measurement technique, which enables measurement of changing curvature with temperature. The included angle of various composite angle bracket specimens is also measured as a function of temperature, using a laser reflection technique.

The results of this testing indicate that tailoring of both non-thermoelastic and thermoelastic components of process-induced distortion can be accomplished. The balancing of the compensation of these effects is shown to result in an angle bracket specimen, which has very little distortion and is much more stable with temperature than the baseline laminate. Further, it is found that the variation in laminate stiffness with changing local laminate stacking sequence plays an important role in the tailoring of the distortion of this geometry. Overall, the results of the research point very clearly to a methodology for the composites engineer to tailor the laminate, and the process, to generate a distortion-free/shape stable angle bracket molded on net-shape tooling.

Keywords

manufacturing distortion warpage anisotropy part—tool interactions.

Get full access to this article

View all access options for this article.

References

Pagliuso, S. ( 1982). Warpage, A Nightmare for Composite Parts Producers, In: Proceedings of the 4th International Conference on Composite Materials , Tokyo, Japan, pp. 1617-1623.

Radford, D.W. and Diefendorf, R.J. ( 1988). Shape Instabilities in Composites Resulting from Laminate Anisotropy, In: Proceedings of the 4th Japan-United States Conference on Composite Materials, Washington, DC .

Nelson, R. and Cairns, D. ( 1989). Prediction of Dimensional Changes in Composite Laminates during Cure, In: 34th International SAMPE Symposium , Reno, NV, Vol. 34, n pt 2, 8-11 May, pp. 2397-2410.

Hammond, M.G. and Farrell, K. ( 1978). Graphite Epoxy Composite Materials Components for Communications Satellites, In: Proceedings of ICCM 2, Metall Soc. of AIME, 16-20 April, pp. 1392-1404.

Radford, D.W. and Rennick, T.S. (2000). Separating Sources of Manufacturing Distortion in Laminated Composites, Journal of Reinforced Plastics and Composites, 19(8): 621-641.

Svanberg, J.M. and Holmberg, J.A. (2001). An Experimental Investigation on Mechanisms for Manufacturing Induced Shape Distortions in Homogeneous and Balanced Laminates, Composites: Part A, 32: 827-838.

Darrow, D.A. and Smith, L.V. ( 2002). Isolating Components of Processing Induced Warpage in Laminated Composites, Journal of Composite Materials, 36(21): 2407-2419.

Wisnom, M.R. , Gigliotti, M. , Ersoy, N. , Campbell, M. and Potter, K.D. ( 2006). Mechanisms Generating Residual Stresses and Distortion during Manufacture of Polymer-matrix Composite Structures, Composites: Part A, 37: 522-529.

Svanberg, J.M. and Holmberg, J.A. (2004). Prediction of Shape Distortions Part I. FE-Implementation of a Path Dependent Constitutive Model , Composites: Part A, 35: 711-721.

10.

Twigg, G. , Poursartip, A. and Fernlund, G. ( 2004). Tool-part Interaction in Composites Processing. Part II: Numerical Modeling, Composites: Part A, 35: 135-141.

11.

Bapanapalli, S.K. and Smith, L.V. (2005). A Linear Finite Element Model to Predict Processing-induced Distortion in FRP Laminates, Composites: Part A, 36: 1666-1674.

12.

Radford, D.W. (1987). Shape Stability in Composites, Doctoral Thesis, Rensselaer Polytechnic Institute.

13.

Albert, C. and Fernlund, G. ( 2002). Spring-in and Warpage of Angled Composite Laminates, Composites Science and Technology, 62: 1895-1912.

14.

Twigg, G. , Poursartip, A. and Fernlund, G. ( 2003). An Experimental Method for Quantifying Tool-part Shear Interaction during Composites Processing, Composites Science and Technology, 63: 1985-2002.

15.

Ersoy, N. , Potter, K. , Wisnom, M.R. and Clegg, M.J. ( 2005). An Experimental Method to Study the Frictional Processes during Composites Manufacturing, Composites: Part A, 36: 1536-1544.

16.

Radford, D.W. (1993). Cure Shrinkage Induced Warpage in Flat Uni-axial Composites, Journal of Composites Technology & Research, 15(4): 290-296.

17.

Chamis, C.C. ( 1978). Residual Stresses in Angleplied Laminates and Their Effects on Laminate Behavior, In: Proceedings of ICCM 2, Metall. Soc. of AIME, 16-20 April, pp. 221-239.

18.

Kim, P. , Phillips, R. , Toll, S. and Manson, J.E. ( 1994). The Dimensional Stability of Composite Laminates: Sensitivity to Gradients in Fiber Content and Misalignment, International Workshop on Advanced Materials for High Precision Detectors , Archamps, France.

19.

Radford, D.W. (1995). Volume Fraction Gradient Induced Warpage in Curved Composite Plates, Composites Engineering , 5(7): 923-934.

20.

Loos, A. and Springer, G. ( 1983). Curing of Epoxy Matrix Composites, Journal of Composite Materials, 17: 135-169.

21.

White, S.R. and Hahn, H.T. (1992). Process Modeling of Composite Materials: Residual Stress Development during Cure. Part I. Model Formulation, Journal of Composite Materials, 26(16): 2402-2422.

22.

White, S.R. and Hahn, H.T. (1992). Process Modeling of Composite Materials: Residual Stress Development During Cure. Part II. Experimental Validation, Journal of Composite Materials, 26(16): 2423-2453.

23.

Hubert, P. , Johnston, A. , Vaziri, R. and Poursartip, A. ( 1995). A Two-dimensional Finite Element Processing Model for FRP Composite Components, In: Proceedings of ICCM-10 , Vancouver, Canada, 14-18 August.

24.

Bogetti, T.A. and Gillespie, J.W. (1991). Two-dimensional Cure Simulation of Thick Composites, Journal of Composite Materials , 25: 239-273.

25.

Bogetti, T.A. and Gillespie, J.W. (1992). Process-induced Stress and Deformation in Thick-section Thermoset Composite Laminates, Journal of Composite Materials, 26(5): 626-660.

26.

Tseng, S.C. ( 1995). Modeling and Simulation of the Thermomechanical Behavior of Fiber Reinforced Thick-Section Structural Components, ASME Paper 95-WA/HT-26.

27.

Radford, D.W. , Fu, S. , Derringer, D. and Davis, J.D. (1999). Measurement of Manufacturing Distortion in Flat Composite Laminates, In: ICCM-12, Paris, France.

28.

Pansare, N.P. and Radford, D.W. (2004). Part-Tool Interaction Induced Distortion on Flat Tooling Plates, 36th International SAMPE Technical Conference, San Diego, CA , 15-17 November.

29.

Twigg, G. , Poursartip, A. and Fernlund, G. ( 2004). Tool-Part Interaction in Composites Processing. Part I: Experimental Investigation and Analytical Model, Composites: Part A, 35: 121-133.

30.

Potter, K.D. , Campbell, M. , Langer, C. and Wisnom, M.R. ( 2005). The Generation of Geometrical Deformations due to Tool/Part Interaction in the Manufacture of Composite Components, Composites: Part A, 36: 301-308.

31.

Radford, D.W. and Fu, S. ( 2003). A Route To Shape Correct/Shape Stable Laminates, In: ICCM-14, San Diego, CA, July 2003.

32.

Melo, J.D.D. and Radford, D.W. ( 1999). Modeling Manufacturing Distortions in Flat, Symmetric, Composite Laminates, 31st International SAMPE Technical Conference, Chicago, IL, 26-30 October.

33.

Sweeting, R. , Liu, X.L. and Paton, R. ( 2002). Prediction of Processing-induced Distortion of Curved Flanged Composite Laminates, Composite Structures, 57: 79-84.

34.

Kamonpet, P. and Radford, D.W. ( 2004). The Effect of Physical Part Constraint on Manufacturing Distortion, In: 36th International SAMPE Technical Conference, San Diego, CA, 15-18 November.

35.

Radford, D.W. and Diefendorf, R.J. (1993). Shape Instabilities in Composites Resulting from Laminate Anisotropy, Journal of Reinforced Plastics and Composites, 12(1): 58-75.

36.

Kollar, L.P. and Springer, G.S. ( 2003). Mechanics of Composite Structures, ISBN 0-521-80165-6 , Cambridge University Press, Cambridge , UK.