Structural Tests of Plastic Frangible Couplings
Tests were conducted on standard frangible couplings and a type of plastic frangible couplings to determine if they were equal to the specified requirements as far as resonant frequency, static loads, and impact loads were concerned. Results indicated that standard metal couplings were congruent with frangibility requirements, but the plastic couplings were not. Under static loads, the plastic units showed excessive bending and, when broken, failed to shear away cleanly. Impact testing indicated that the plastic couplings were much too sinewy to meet the frangibility standards presently required of the standard couplings. Additional considerations in selection of a material for frangible couplings should also include temperature, electrical conductivity, and fatigue factors, none of which were covered in the present test series.
FAA-RD-76-202
Author: Bret B. Castle