Composite material stiffness coefficient nondestructive measurement method

Abstract

The invention discloses a composite material stiffness coefficient non-destructive recognition method based on an ultrasonic Lamb wave technology. The method comprises the four parts including direct problem theoretical modeling, sensitivity analysis, measurement of phase velocity value by experiments and stiffness coefficient inverse problem solving; for a direct problem theoretical model, the self derived novel third-order plate theory is used for solving the spread theoretical phase velocity value of Lamb waves in a composite material plate; the theory considers the plate wave stress free boundary conditions; the complicated step of shearing correction factor calculation required by the ordinary plate theory is avoided; for the sensitivity analysis, the proper spreading angle and the Lamb wave mode are selected, and are the premise for complete reconstruction of nine stiffness coefficients; the experiment uses a non-contact type laser ultrasonic system, and an advanced signal processing method is combined, so that the multi-angle waveguide phase velocity value measurement is completed; finally, an intelligent optimization algorithm is combined; the optimal solution of the composite material stiffness coefficient is obtained through the minimum experimental measurement phase velocity value and the theoretical calculation phase velocity value.

Description

Technical field: [0001] The invention designs a non-contact method for measuring mechanical performance parameters of composite materials, and in particular relates to a non-destructive measurement method for stiffness coefficient of composite materials, which belongs to the technical field of performance evaluation of composite materials. Background technique: [0002] Carbon fiber composite materials are widely used in aerospace, automobile and shipbuilding industries due to their high specific strength, specific stiffness and corrosion resistance. However, the mechanical property analysis and structural design of composite materials must be based on sufficient and accurate performance data. At the same time, in the process of composite material processing and production, it is also necessary to evaluate the mechanical properties of the composite material to strictly monitor the implementation of the processing technology and prevent the existence of defects such as compos...

AI Technical Summary

Problems solved by technology

At present, most researchers use the method of pasting piezoelectric sheets (or piezoelectric sheet arrays) on the surface of the test piece to excite or receive Lamb waves. This contact detection method may cause debonding of piezoelectric sheets during the service of composite materials. , the change of sensor-structure coupling conditions will lead to inaccurate measurement results or experimental failure, which cannot meet the needs of in-situ detection; in addition, limited by the size of the piezoelectric sheet, this method can only measure the group velocity value of the guided wave propagation , instead of the phase velocity value, correspondingly increases the complexity of the calculation of the forward problem (that is, the problem of solving the guided wave velocity with known material stiffness)

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