The layer removal method is often used for measurement of internal stresses in homogeneous polymer materials. In order to extend the use of the method to polymer composites, certain refinements are needed. These include (1) use of varying mechanical properties (elastic moduli) through the thickness of the composite plate and (2) measurement of not only curvatures but also strains. These refinements are necessary because a nonsymnetric laminate is created when layers are removed. The modified layer removal method was applied to PEI-glass fiber composite cross-ply laminates. The average internal stresses measured within a layer of constant fiber orientation agree well with stress levels predicted by Classical Lamination Theory. The computed stress levels fulfill the condition of stress equilibrium, indicating that the procedure applied in the measurements is correct.
1. Hart-Smith, L. J. 1991. "The Role of Biaxial Stresses in Discriminating Between Meaningful and Illusory Composite Failure Theories,"9th DoD/NASA/FAA Conference on Fibrous Composites in Structural Design, Nevada.
2.
2. Evans, B. L.1989. "The Optical Birefringence of Injection-Moulded Polystyrene and Polyethylene,"J. of Materials Science, 24:3588-3588.
3.
3. Unger, W. J. and J. S. Hansen. 1993. "The Effect of Thermal Processing on Residual Strain Development in Unidirectional Graphite Fibre Reinforced PEEK,"J. of Composite Materials, 27(1):59-59.
4.
4. Manson, J-A. E. and J. C. Seferis. 1992. "Process Simulated Laminate (PSL): a Methodology to Internal Stress Characterization in Advanced Composite Materials,"J. of Composite Materials, 26(3):405-405.
5.
5. Peiter, A.1966. Eigenspannungen I. Art: Ermittlung und Bewertung, Dusseldorf: Michael Tritsch Verlag.
6.
6. Barret, C. S. and P. Predecki. 1976. "Stress Measurement in Polymeric Materials by X-Ray Diffraction,"Polymer Engineering and Science, 16:602-602.
7.
7. Jagers, C. E. M.1988. "Observation Techniques for Molecular Orientation in Amorphous Polymers," IOP report project 9.2, University of Twente, Netherlands.
8.
8. Hahn, H. T. and D. G. Hwang. 1981. "Residual Stresses and Their Effects in Composite Laminates,"Proc. of NCKU/AAS Int. Symp. on Engineering Sciences and Mechanics, Taiwan.
9.
9. Powell, P. C.1994. Engineering with Fibre-Polymer Laminates, London: Chapman & Hall.
10.
10. Yu, W., P. Sunderland and J-A. E. Manson. 1994. "A Method for the Measurement of Internal Stresses in Laminated Composites: the Successive Grooving Technique,"Proc. ANTEC 94, 11:2045-2045.
11.
11. Hastenberg, C. H. van, P. C. Wildervanck, A. J. H. Leenen and G. G. J. Schennink. 1993. "The Measurement of Thermal Stress Distributions Along the Flow Path in Injection Moulded Flat Plates,"Polymer Engineering and Science, 32:7-7.
12.
12. Hindle, C. S., J. R. White, D. Dawson and K. Thomas. 1992. "Internal Stress, Molecular Orientation, and Distortion in Injection Moldings: Polypropylene and Glass-Fibre Filled Polypropylene,"Polymer Engineering and Science, 32(3):157-157.
13.
13. Zoetelief, W. F. 1990. Internal Stresses in Injection Mouldings, M.Sc. Thesis, University of Twente, Netherlands.
14.
14. Jeronimidis, G. and T. Parkyn. 1988. "Residual Stresses in Carbon Fibre-Thermoplastic Matrix Laminates,"J. of Composite Materials, 22:401-401.
15.
15. Chapman, T. J., J. W. Gillespie, Jr., R. B. Pipes, J-A. E. Manson and J. C. Seferis. 1990. "Prediction of Process Induced Residual Stresses in Thermoplastic Composites,"J. of Composite Materials, 24:616-616.
16.
16. White, J. R.1985. "On the Layer Removal Analysis of Residual Stress, Part 1: Polymer Mouldings with Depth Varying Young's Modulus,"J. of Materials Science, 20:377-377.
17.
17. Paterson, M. W. A. and J. R. White. 1989. "Layer Removal Analysis of Residual Stress, Part 2: A New Procedure for Polymer Mouldings with Depth Varying Young's Modulus,"J. of Materials Science, 24:3521-3521.
18.
18. Treuting, R. G. and W. T. Read. 1951. "A Mechanical Determination of Biaxial Residual Stress in Sheet Materials,"J. of Applied Physics, 22(2):130-130.
19.
19. Lange, J., A. Hult and J-A. E. Manson. 1993. "Stress Build-Up during the Reaction of Thermoset Films Cured Above Their Ultimate T,,"Proc. of the American Chemical Society Division of Polymeric Materials: Science and Engineering, 68:222-222.
20.
20. Kim, K. S. and H. T. Hahn. 1989. "Residual Stress Development during Processing of Graphite/Epoxy Composites,"Composites Science and Technology, 36:121-121.
21.
21. Kim, K. S., H. T. Hahn and R. B. Croman. 1989. "The Effect of Cooling Rate on Residual Stress in a Thermoplastic Composite,"J. of Composite Technology & Research, 11(2):47-47.
22.
22. Hyer, M. W.1981. "Calculations of the Room-Temperature Shapes of Unsymmetric Laminates,"J. of Composite Materials, 15:296-296.
23.
23. Peeters, L. J. B., P. C. Powell and L. Warnet. 1995. "Thermally Induced Shapes of Unsyrnmetric Laminates,"J. of Composite Materials, 29(15).
