Effect of Elevated Temperatures on the Mechanical Performance of Pultruded FRP Joints with a Single Ordinary or Blind Bolt

Presented in this paper is a combined experimental and analytical modeling study of the strength of pultruded fiber-reinforced polymer (FRP) single-bolted double-lap joints subjected to tensile loading and elevated temperatures. Dynamic mechanical analysis (DMA) and thermogravimetric analysis (TGA) are conducted on the polymeric composite material to determine the glass transition temperature and decomposition temperature, respectively. Based on the DMA and TGA results, and to cover glass transition without any material decomposition, the six temperatures selected for the test program are +23, +60, +100, +140, +180, and +220 degrees C. Three nominally identical joints are tensioned to failure at each temperature. A total of 36 double-lap joints are tested, comprising 18 joints fabricated with ordinary steel bolting and the other 18 with novel blind bolting. A comparison is made based on load-displacement curves, failure modes, and maximum (ultimate) loads. It is found that both methods of mechanical fastening experience a reduction of 85% in maximum load as the test temperature increases from +23 to +220 degrees C. Three proposed empirical or mechanism-based models for characterizing strength under elevated temperatures are shown to provide good predictions for the maximum loads obtained in the test program.