Predicting the stacking sequence of E-glass fiber reinforced polymer (GFRP) epoxy composite using terahertz time-domain spectroscopy (THz-TDS) system

A terahertz time-domain spectroscopy (THz-TDS) system was used for measuring and predicting stacking sequence of laminated composites. The THz wave's penetration behavior in emissivity (E)-glass fiber reinforced polymer epoxy composites was analyzed. The relationship between polarization angle of THz radiation to fiber direction of the composites and dielectric constant in THz frequency range was formulated using a two-dimensional transformation matrix. Then, the dielectric constants of arbitrarily laminated composite plates were calculated by combining the transformation matrix via laminating rule. The dielectric constants of the arbitrarily laminated composites were measured and compared with those of the developed theoretical models. It was found that the THz waves could be successfully used to predict the stacking sequence of the laminated composites with 0.25% error.