The Natural Modes of Graphite/Epoxy Cantilever Plates and Shells

The natural frequencies and mode shapes of a number of Graphite/ Epoxy and Graphite/Epoxy-Aluminum plates and shells were experimen tally determined. The samples tested include 8 ply Graphite/Epoxy plates, cyclindrical shell sections, and Graphite/Epoxy-Aluminum hybrid plates of various laminates and aspect ratio. Fabrication and test procedures are described. Natural frequency and mode shape results are compared with those calculated by a finite element analysis. Agreement between calcu lated and observed mode shapes is excellent; while reasonable agreement is found for frequencies. Among the sources of this discrepancy in frequency results is the possibility of a difference between dynamic-flexural moduli and static in-plane moduli.