A Real-Time NDT Method Based on FBG Sensor Spectrums to Detect the Transverse Matrix Cracks in Composite Materials

Abstract

Transverse matrix cracking is probably the first and most dominant mode of damage in composite materials. In this paper, a real-time Non-Destructive Testing (NDT) method was proposed to detect the transverse cracks by Fiber Bragg Grating (FBG) sensors. The experiment of observing the crack growth and recording FBG’s reflection spectrums as well as Finite Element Method (FEM) methods were conducted to help verifying the regularities of the reflection spectrum distortions in the cracking angle-ply [0n/ ± θm/0n] laminates. The results showed that the shape of the spectrum was highly correlated to the crack density of composites. From undamaged state to high crack density conditions, the shape of the spectrum experienced an ‘original-splitting-regressive’ process. Under the assumed ideal periodic strain distribution conditions, the peak width w of the reconstructed spectrums and crack density $$\rho$$ showed very good linearity which provided the possibility for quantitative detection of the crack density of composites.