The authors have applied newly developed small − diameter Fiber Bragg Gratillg ( FBG ) sensors , whose cladding was 40 μ m in Cliameter , for the detection of transverse crackS in Carbon Fiber Reinforced Plastic ( CFRP )quasi −isotropic laminates. Load − ing / unloading test was carried out , and re 且ectiQn spectra from the FBG sensor were measured at various tensile strain . When transverse cracks occured in the laminate , the shape of reflection spectrum was drastically distorted , and the

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... Width at Quarter Maximum ( FWQM ) increased in proportion to the transeverse crack density in the 90 °ply . This Change in the form of the spectrum could be confirmed by the theoretical calcUlation . 1(ey Wo 冠 5 : CFRP Laminates , ] lansverse Cracks , Smal1 − Diameter Optical Fiber , FBG Sensor