Moisture Absorption/Desorption Effects on Flexural Property of Glass-Fiber-Reinforced Polyester Laminates: Three-Point Bending Test and Coupled Hygro-Mechanical Finite Element Analysis

Abstract

Influence of moisture absorption/desorption on the flexural properties of Glass-fibre-reinforced polymer (GFRP) laminates was experimentally investigated under hot/wet aging environments. To characterize mechanical degradation, three-point bending tests were performed following the ASTM test standard (ASTM D790-10A). The flexural properties of dry (0% M t /M 8 ), moisture unsaturated (30% M t /M 8 and 50% M t /M 8 ) and moisture saturated (100% M t /M 8 ) specimens at both 20 and 40˝C test temperatures were compared. One cycle of moisture absorption-desorption process was considered in this study to investigate the mechanical degradation scale and the permanent damage of GFRP laminates induced by moisture diffusion. Experimental results confirm that the combination of moisture and temperature effects sincerely deteriorates the flexural properties of GFRP laminates, on both strength and stiffness. Furthermore, the reducing percentage of flexural strength is found much larger than that of E-modulus. Unrecoverable losses of E-modulus (15.0%) and flexural strength (16.4%) for the GFRP laminates experiencing one cycle of moisture absorption/desorption process are evident at the test temperature of 40˝C, but not for the case of 20˝C test temperature. Moreover, a coupled hygro-mechanical Finite Element (FE) model was developed to characterize the mechanical behaviors of GFRP laminates at different moisture absorption/desorption stages, and the modeling method was subsequently validated with flexural test results.

Coupled Hygro-Mechanical Finite Element Method on Determination of the Interlaminar Shear Modulus of Glass Fiber-Reinforced Polymer Laminates in Bridge Decks under Hygrothermal Aging Effects

“…From the transient-field FE moisture diffusion analysis, the moisture concentration distribution across the short-beam GFRP specimen section is obtained as a function of time, which can be read into the following stress–strain analysis as a predefined field variable at different time intervals. To determine the environment-dependent interlaminar shear modulus of FRP laminates, the coupled hygro-mechanical FE modeling method is employed herein, which was already well developed and validated by flexural tests in the previous research [31]. For instance, at the test temperature of 20 °C and during the moisture absorption process, the flexural modulus (E11 and E22) of GFRP laminates with a nominal moisture content ( M t / M ∞ ) from 0% to 100% can be calculated using the predictive equations (available in the Ref.…”

“…For instance, at the test temperature of 20 °C and during the moisture absorption process, the flexural modulus (E11 and E22) of GFRP laminates with a nominal moisture content ( M t / M ∞ ) from 0% to 100% can be calculated using the predictive equations (available in the Ref. [31] of Jiang et al). It is employed as field-dependent input values for material properties of the FE model herein, which means the flexural modulus of each element is determined by the local moisture concentration.…”

“…Furthermore, it is assumed that degradation of interlaminar shear modulus follows a linear relationship with nominal moisture content, which has the same tendency as that obtained from the flexural modulus of GFRP laminates [31]. Subsequently, the interlaminar shear modulus of GFRP specimens with 0% moisture content (S-0%-20 °C) is firstly determined by fitting the FE load–deflection curve to test results, as shown in Figure 10a.…”

Effects of acid, alkaline, and seawater aging on the mechanical and thermomechanical properties of glass fiber/epoxy composites filled with carbon nanofibers

“…These effects are reversible in the early stages of aging if the absorbed water is eliminated, and no chemical reaction takes place. Moreover, extended water adsorption generally leads to irreversible changes within the fiber surface, the matrix, and the fiber/matrix interface . Water also causes lowering of the glass‐transition temperature ( T g ).…”

Dependency of cohesive laws of a structural adhesive in Mode-I and Mode-II loading on moisture, freeze-thaw cycling, and their synergy

“…Environmental effects, particularly moisture and thermal cycles, can severely affect the mechanical properties of adhesives [21][22][23][24][25]. Moisture, which can take the form of humidity, liquid water or de-icing salt solutions, mainly affects adhesives through plasticisation, swelling, cracking and hydrolysis [26][27][28][29]. Cyclic freeze-thaw exposure is also a concern in many countries where it represents a typical outdoor condition [30].…”