Experimental Verification of Spline Stress Analysis Method for a Structural Composite Laminate Containing a Hole

Abstract

Moire interferometry surface strain measurements for a uniaxially loaded composite laminate with an open hole were compared to predictions from threedimensional spline variational theory, from two-dimensional finite element analysis, and from two-dimensional elasticity theory. Strain measurements and a progressive damage investigation were accomplished using twenty-eight ply fiber dominated, IM7/5250-4, laminates. At low load levels, prior to matrix cracking, phase shifting moire interferometry was used to measure in-plane displacements. Experimental surface strains were calculated based on digital analysis of the displacement fields. Direct comparisons between theory and experiment were made using contour plots of ex,, Eyy, and yxy. For all in-plane surface strains, the spline variational theory results showed good agreement with experiment in close proximity to the hole. A separate group of specimens were loaded incrementally until failure, and the initiation and progression of damage was documented using x-ray images. Regions where the stress exceeded the ultimate transverse strength are compared to the actual damage images using contour plotting schemes. Overall, the location of initial failure as predicted by the spline variational theory corresponded well with damage observations for early stages of damage.

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References

1996. ANSYS Rev 5.2. Swanson, Houston, PA: Analysis System Inc.

Creath, K. 1988. "Phase-Measurement Interferometry Techniques," Progress in Optics, 26:350-393.

Eisenmann, J. R. 1976. Bolted Joint Static Strength Modelfor Composite Materials, NASA TM-X3377, pp. 563-602.

Garbo, S. P. and J. M. Ogonowski . 1981. "Effect of Variances and Manufacturing Tolerances on the Design Strength and Life of Mechanically Fastened Composite Joints," Vols. 1, II, and III, AFWALTR-81-3041.

Garbo, S. P. and J. M. Ogonowski . 1978. Effect of Variances and Manufacturing Tolerances on the Design Strength and Life of Mechanically Fastened Composite Joints, AFWAL-TR-78-179.

Grant, P. and A. Sawicki . 1991. "Development of Design and Analysis Methodology for Composite Bolted Joints," Meeting on Rotorcraft Structures, Williamsburg, VA.

Iarve, E. V. 1996. "Spline Variational Three-Dimensional Stress Analysis of Laminates with Open Holes," International Journal of Solids and Structures, 33(14):2095-2118.

larve, E. V. 1995. "Three-Dimensional Stress Analysis of Fastener Hole Composites," AMD-Vol. 69-1, IMECE, American Society of Mechanical Engineering.

Lassahn, G. , P. Taylor , V. Deason and J. Lassahn . 1994. "Multiphase Fringe Analysis with Unknown Phase Shifts," Optical Engineering, 33(6):2039-2044.

10.

Lekhnitskii, S. G. 1968. Anisotropic Plates, Gordon and Breach Science Publishers.

11.

Mollenhauer, D. , P. Ifju and B. Han . 1994. "A Compact, Robust, and Versatile Moire Interferometer," Optics and Lasers in Engineering, Vol. 22, pp. 29-40.

12.

Perry, K. and J. McKelvie . 1993. "A Comparison of Phase Shifting and Fourier Methods in the Analysis of Discontinuous Fringe Patterns," Optics and Lasers in Engineering, 19:269-284.

13.

Post, D. , B. Han and P. Ifju . 1994. High Sensitivity Moire.: Experimental Analysis for Mechanics and Materials, Springer-Verlag Inc., New York.

14.

Pullman, D. and J. R. Schaff . 1996. "Three Dimensional Spline Variational and Finite Element Theory: A Comparison for a Laminate with a Circular Hole," 11th Technical Conference on Composite Materials, W. S. Johnson , Ed., American Society for Composites.

15.

Shyprykevich, P. 1995. "Characterization of Bolted Joint Behavior: MIL-HDBK-17. Accomplishments at Standardization," Journal of Composites Technology and Research, JCTRER, 17(3):260-270.

16.

Snyder, B. D. , J. G. Burns and V. B. Venkayya . 1990. "Composite Bolted Joints Analysis Programs," Journal of Composites Technology and Research, JCTRER, 12(1):41-51.