How strong are the composite blades?
Clearly the blades are not as strong or as stiff as bronze, but the issue is – are they strong enough for the purpose for which they have been designed. Virtually all modern aircraft have composite propellers. Zytel contains ~ 35 % glass by weight and is thus both very strong and stiff. The black colouring is not carbon based and thus does not have a corrosion potential. DuPont have extensive technical information on their web page regarding the physical characteristics of the many different grades of Zytel they have available. By choosing a 3 bladed design over a 2 bladed unit the forces involved are immediately reduced to 33 % per blade vs 50 % – a 33 % reduction. Another design issue is that composites and the economics they enjoy allow a blade to be sacrificed in a catastrophic situation. With a substantial impact on the blade tips ( always the first part to hit ) they invariably tear from the mounting hole outwards leaving the castings undamaged. We believe it is better to loose a
