Nondestructive evaluation of residual stress in short-fiber reinforced plastics by x-ray diffraction

Keisuke Tanaka; Syouhei Tokoro; Yoshiaki Akiniwa; Noboru Egami

doi:10.1117/12.2054128

2 June 2014 Nondestructive evaluation of residual stress in short-fiber reinforced plastics by x-ray diffraction

Keisuke Tanaka, Syouhei Tokoro, Yoshiaki Akiniwa, Noboru Egami

Proceedings Volume 9234, International Conference on Experimental Mechanics 2013 and Twelfth Asian Conference on Experimental Mechanics; 92340U (2014) https://doi.org/10.1117/12.2054128
Event: International Conference on Experimental Mechanics 2013 and the Twelfth Asian Conference on Experimental Mechanics, 2013, Bangkok, Thailand

Abstract

The X-ray diffraction method is used to measure 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%. Based on the orientation of carbon fibers, injection molded plates can be modeled as three-layered lamella where the core layer is sandwiched by skin layers. The stress in the matrix in the skin layer was measured using Cr-Kα radiation with the sin²Ψ method. Since the X-ray penetration depth is shallow, the state of stresses measured by X-rays in FRP can be assumed to be plane stress. The X-ray measurement 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, σ₁^m, and perpendicular to the fiber direction, σ₂^m, and shear stress τ₁₂^m can be expressed as the functions of the applied (macro-) stresses, σ₁^A, σ₂^A , τ₁₂^A as follows: σ₁^m = α₁₁σ₁^A +α₁₂σ₂^A, σ₂^m = α₂₁σ₁^A + α₂₂σ₂^A, τ₁₂^m = α₆₆τ₁₂^A, where α₁₁ ,α₁₂, α₂₁, α₂₂, α₆₆ are stress-partitioning coefficients. Using skin-layer strips cut parallel, perpendicular and 45° to the molding direction, the stress in the matrix was measured under the uniaxial applied stress and the stress-partitioning coefficients of the above equations were determined. Once these relations are established, the macrostress in SFRP can be determined from the measurements of the matrix stresses by X-rays.

Citation Download Citation

Keisuke Tanaka, Syouhei Tokoro, Yoshiaki Akiniwa, and Noboru Egami "Nondestructive evaluation of residual stress in short-fiber reinforced plastics by x-ray diffraction", Proc. SPIE 9234, International Conference on Experimental Mechanics 2013 and Twelfth Asian Conference on Experimental Mechanics, 92340U (2 June 2014); https://doi.org/10.1117/12.2054128

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