Material Characterization by the Finite Element Method

A Newton-Raphson method combined with a weighted least square technique using experimental data (measured displacements) is developed in order to determine the stiffness coefficients of elastic composite materials. A finite element static analysis of the structure is performed using approximate stiffness coefficients. The exact coefficients are determined by successive iterations by comparing some of the computed displacements to measured displacements. Preliminary tests indicate that this technique is useful for predicting the appropriate experimental conditions. Secondly, the procedure converges rapidly, even for very poor starting ap-proximations of the stiffness coefficients, provided the loading conditions are favorable. Finally, the technique reveals to be sensitive to measurement errors despite the use of a weighting factor in the least square technique. SCOPE HE AIM OF THIS work is the determination of the mechanical properties oflinearly elastic and homogeneous materials. The main working assump-tion is that heterogeneous materials can be replaced by equivalent homogeneous materials with properties to be determined. These mechanical properties are the stiffness coefficients, i.e. the terms of the Hooke matrix. The present method is based on an iterative procedure using experimental data obtained from a static loading test together with numerical results of a finite element analysis of the same test