Evaluation of mechanical properties of glass fiber-reinforced composites depending on length and structural anisotropy

Abstract

Recently, as the size of liquid natural gas (LNG) carriers has dramatically increased, applied force in the LNG Cargo Containment System (CCS) has also increased. However, the existing E-glass fiber-reinforced composite, which plays an important role to prevent accident as secondary barrier induced LNG leakage, has remained unchanged. In case of in-situ length of the composite in membrane type of MARK-III LNG CCS, it is continuously installed as a prolonged structure by using automatic bonding machine (ABM). From this point of view, it should be considered that the length effect of the mechanical properties to represent an infinitely long distance for structural reliability. Fracture strength of a brittle material, such as glass fiber components, is generally not constant because of the variable quantity and distribution of imperfections throughout the composites. In this study, 2-parameters of Weibull distribution were derived to standardize the widely dispersed fracture strengths under the quasi-static tensile test condition. As a result of the experiments by length, the standardized failure strength associated with scale parameter (63.2% probability of failure over all the repeated tests) in the Weibull distribution increases until it reaches a specific length at 250 mm, at which point it stops rising and converges to a constant value. This tendency indicates that material properties at the specific length will be reliable for mechanical evaluation of the composites under the infinitely prolonged condition.