Residual Stress Evaluation of Short-Fiber Reinforced Plastics by X-Ray Diffraction

Abstract:

The X-ray diffraction method is used to evaluate the residual stress in injection-molded plates of short-fiber reinforced plastics (SFRP) made of crystalline thermoplastics, polyphenylene sulphide (PPS), reinforced by carbon fibers with 30 mass%. The stress in the matrix in the skin layer was determined using Cr-Kα radiation with the sin² ψ method. The X-ray evaluation of stress in carbon fibers was not possible because of high texture. A new method was proposed to evaluate the macrostress in SFRP from the measurement of the matrix stress. According to micromechanics analysis of SFRP, the matrix stresses in the fiber direction and perpendicular to the fiber direction, and shear stress can be expressed as linear functions of the applied (macro-) stresses in the fiber direction and perpendicular to the fiber direction, and shear stress. The proportional constants are named stress-partitioning coefficients. Using skin-layer strips cut parallel, perpendicular and 45° to the molding direction, the stress in the matrix was evaluated under the uniaxial applied stress and the stress-partitioning coefficients of the above equations were determined. Once the relations between the macrostress and matrix stress are established, the macrostress in SFRP can be evaluated from the measurements of the matrix stresses using X-rays.

• Periodical: Advanced Materials Research (Volume 996)
• Pages: 951-957
• DOI: https://doi.org/10.4028/www.scientific.net/AMR.996.951
• Online since: August 2014
• Authors: Keisuke Tanaka*, Yuuki Koike, Yoshiaki Akiniwa
• Keywords: Micromechanics, Residual Stress, Short-Fiber Reinforced Plastics, X-Ray Measurement

References

[1] J. Karger-Kocsis, Fracture of short-fiber reinforced thermoplastics, in: K. L. Reifsnider (Ed. ), Application of Fracture Mechanics to Composite Materials, L., Elesevier Science Pub., Amsterdam, (1989) 189-247.

DOI: 10.1016/b978-0-444-87286-9.50010-3

[2] J. F. Mandell, Fatigue behavior of short fiber composites materials, in: K. L. Reifsnider (Ed. ), Fatigue of Composites, Elesevier Science Pub., Amsterdam, (1990) 231-337.

[3] J. Karger-Kocsis and K. Friedlich, Microstructural details and the effect of testing conditions on the fracture toughness on injection-molded poly(phenylene-sulphide) composites, Journal of Materials Science, Vol. 22 (1987) 947-961.

DOI: 10.1007/bf01103535

[4] K. Tanaka, K. Suzuki and Y. Akiniwa, Evaluation of Residual Sresses by X-Ray Diffraction, Yokendo, Tokyo (2006).

[5] K. Tanaka, S. Tokoro, N. Egami and Y. Akiniwa, X-ray residual stress measurement of short-fiber reinforced plastics, Proceeding of the 47th Symposium of X-Ray Studies of Mechanical Behavior of Materials, The Society of Materials Science, Japan, (2013).

DOI: 10.1117/12.2054128

[6] B. J. Tabor, E. P. Magre and J. Boon, The crystal structure of poly-p-phenylene sulphide, European Polymer Journal, Vol. 7 (1971) 1127-1133.

DOI: 10.1016/0014-3057(71)90145-5

[7] J. S. Chung, J. Bodzich and P. Chee, Effects of thermal history on crystal structure of poly(phenylene sulphide), Journal of Materials Science, Vol. 27 (1992) 5609-5619.

DOI: 10.1007/bf00541631

[8] J. D. Eshelby, The determination of the elastic field of an ellipsoidal inclusion, and related problems, Proceedings of Royal Society, London, Vol. A241 (1957) 376-396.

[9] T. Mori and K. Tanaka, Average stress in matrix and average energy of materials with misfitting inclusions, Acta Metallugica, Vol. 21 (1973) 571-574.

DOI: 10.1016/0001-6160(73)90064-3