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The interlaminar shear modulus of cardboards was measured using torsional vibration (TV) and flexural vibration (FV) methods. In the TV method, the sample widths were decreased during the tests, and the interlaminar and in-plane shear moduli were determined using the data obtained based on the different widths. By contrast, in the FV method, the resonance frequencies from the first to third FV modes were measured using samples of various lengths, and the interlaminar shear modulus and Young's modulus in the length direction were calculated using Timoshenko's vibration theory. In addition to the experiment, modal analyses based on the finite element (FE) method were performed, and the sample configurations used to accurately obtain the interlaminar shear modulus were experimentally and numerically investigated. The TV method did not allow the interlaminar shear modulus to be obtained appropriately because the vibration behavior often deviated from that theoretically derived by the TV equation. By contrast, the FV method allowed the interlaminar shear modulus to be obtained appropriately for a wide range of sample lengths. [ABSTRACT FROM AUTHOR]

To investigate the mechanical degradation of the shear properties of glass fiber-reinforced polymer (GFRP) laminates in bridge decks under hygrothermal aging effects, short-beam shear tests were performed following the ASTM test standard (ASTM D790-10A). Based on the coupled hygro-mechanical finite element (FE) analysis method, an inverse parameter identification approach based on short-beam shear tests was developed and then employed to determine the environment-dependent interlaminar shear modulus of GFRP laminates. Subsequently, the shear strength and modulus of dry (0% Mt/M∞), moisture unsaturated (30% Mt/M∞ and 50% Mt/M∞), and moisture saturated (100% Mt/M∞) specimens at test temperatures of both 20 °C and 40 °C were compared. One cycle of the moisture absorption–desorption process was also investigated to address how the moisture-induced residual damage degrades the shear properties of GFRP laminates. The results revealed that the shear strength and modulus of moisture-saturated GFRP laminates decreased significantly, and the elevated testing temperature (40 °C) aggravated moisture-induced mechanical degradation. Moreover, an unrecoverable loss of shear properties for the GFRP laminates enduring one cycle of the moisture absorption–desorption process was evident. [ABSTRACT FROM AUTHOR]