AN INSTRUMENTED FASTENER FOR SHEER FORCE MEASUREMENTS IN JOINTS

A preliminary investigation has been conducted on instrumented fastene rs for use as sensors to measure the shear loads transmitted by indivi dual fasteners installed in double-splice joints. Calibration and load verification tests were conducted for instrumental fasteners installe d at three fastener torque levels. Results from calibration tests show that the shear strains obtained from the instrumented fasteners vary linearly with the applied load and that the instrumental fasteners can be effectively used to measure shear loads transmitted by individual fasteners installed in double-splice joints. Tests were also conducted with three instrumented fasteners installed in a typical double-splic e joint. The test results showed that the load distribution between in dividual fasteners is dependent on the location of the fastener in the joint and the fastener torque level. The fastener located near the en d of the joint with the single plate carried more load the the fastene rs located near the end of the joint with the two plates. Installing t he fasteners with a torque greater than finger tight results in a sign ificant amount of the load being carried by friction between the fayin g surfaces of the plates even if the faying surfaces are polished and lubricated. Increasing the fastener torque also results in a more unif orm distribution of the loads between the individual fasteners for joi nts in aluminum plates with two fasteners, but does not have a signifi cant effect for joints in steel plates with three fasteners.