THREADED JOINTS IN GLASS-FIBER-REINFORCED POLYAMIDE

Threaded joints can be used to join different polymers or polymers to metals at high loads. Design with self-threading screws or threaded in serts requires dynamic mechanical properties. Results are presented on threaded joints of glass fiber reinforced polyamide 6 under static an d dynamic loads. Dynamic load limits are determined by using the hyste resis measurement method with stepwise load increment experiments and single load level experiments. The failure and fatigue behavior of thr eaded joints is characterized by several parameters calculated from th e hysteresis loop. These parameters change in a characteristic manner as a function of load and time. Significant changes exhibited by the d amping and stiffness curves in stepwise load increase experiments can be used to determine the loss of preload on the screw and the beginnin g of screw pull out. Specially designed self threading screws for thre aded joints capable of bearing high dynamic loads are discussed. These joints can attain a life in the endurance range (10(6) cycles) withou t loss of preload. In comparison with S-N curves, the dynamic load lim its for threaded joints can be determined more quickly by the hysteres is measurement method.