Characterization of mechanical properties by inverse technique for composite reinforced by knitted fabric. Part 2. Experimental evaluation of mechanical properties by frequency eigenvalues method

This paper is the second part of the research work dedicated to evaluation of mechanical properties of polymer composites reinforced by knitted fabric. Three different approaches were applied for the task. Two of them: a) FEM analysis using Solid Works combined with structural modeling based on experimentally-determined mechanical and geometrical properties of the reinforcement and matrix, and b) direct measurement of mechanical properties (described in Part 1). Present investigation (Part 2) is based on application of vibrational analysis. Modal testing in combination with the mathematical optimization procedure were used for evaluation of elastic properties of a layered material. It is worth mentioning that the application of this approach for materials with high damping ability (laminated composites reinforced by knitted fabric) is still poorly investigated. The inverse technique exploited in this work is based on the direct orthotropic plate free vibration measurements and subsequent mathematical optimization procedure (the planning of experiments or response surface technique), which is based on minimization of error functional. Finally, elastic constants established by the inverse technique were discussed and compared with the results obtained in Part 1.