Recently, the use of GMT (Glass-Mat reinforced Thermoplastics) composites made of polypropylene and glass fiber has greatly increased due to its many advantages. GMT has attractive mechanical properties such as high specific stiffness, high specific strength, and high impact energy absorption. It is also relatively cheap and easily recyclable. Although GMT composites have sufficient mechanical properties to be used as structural components, the joining of composite materials with other components often reduce their merits because the joints are often the weakest areas in composite structures.
In this study, bolted joint tests for GMT specimens under tensile loading were carried out to investigate the relation between bearing strength and glass fiber weight fraction. The effect of varying the mold area of a GMT plate and molding temperature were also examined. It was also found that the initial GMT plates and different regions of GMT plates had different fiber weight fractions ranging from 32% to 43%. Since the fiber weight fraction directly influences the bearing strength, experimental strength data were modified in proportion to the fiber weight fraction values of specimens. That is, the local fiber weight fraction of GMT plates after the molding process was considered to modify the bearing strength of the bolted joint. Thereafter, the geometry of the specimen was considered. The minimum end distance and width of the specimen to induce the bearing fracture mode of the bolted joint were found. And finally, the effect of washer outer diameter and clamping pressure on the bearing strength were also investigated.
