Static and fatigue behavior of pultruded FRP multi-bolted joints with basalt FRP and hybrid steel-FRP bolts

Abstract

This study investigates the effect of bolt types on the static and fatigue performance of basalt fiber-reinforced polymer (BFRP) multi-bolted double-lap connections. Three types of bolts are used: stainless-steel (SS), BFRP, and hybrid steel-FRP (HSFRP) bolts. Firstly, static tensile tests using steel single-bolted double-lap connections are conducted to determine the mechanical properties and failure modes of the proposed bolts. Secondly, static and fatigue tests using BFRP double-lap connections with six bolts of either SS, BFRP, or HSFRP were conducted. Finally, post-fatigue static tests were conducted to evaluate the deterioration of the composite joints caused by fatigue loading. Load-displacement curves, failure modes, fatigue life, S-N curves, and stiffness degradation are used to evaluate the effect of the bolt type on the behavior of the BFRP joints. Results indicated that SS bolts can be replaced entirely with BFRP bolts without affecting the static and fatigue performance of the joints. In addition, compared to the brittle failure of both the SS and BFRP bolts, the proposed HSFRP bolts exhibited ductile behavior which could be the key to achieving ductile composite structures. Moreover, the HSFRP bolts dramatically prolonged the fatigue life of the composite joints compared to the joints with SS and BFRP bolts.