A Method for Measuring Out-of-Plane Stiffness of Composite Materials by Multi-point Bending

Abstract

The invention discloses a method for multi-point bending measurement of composite material out-of-plane stiffness, and belongs to the aviation structural mechanics field. With utilization of various stress field distribution formed in a test piece, having both a pure shearing state and a coupling state and formed by a simple multi-point bending test method especially a simple five-point bending test method, and at the same time, with utilization of a parameter inversion method, optimization inversion calculation is carried out according to a finite element model result and multiple out-of-plane stiffness data can be obtained at a time. The method for multi-point bending measurement of the composite material out-of-plane stiffness has high accuracy of measurement results, and eliminates a coupling effect between the stiffness. The composite material out-of-plane stiffness data results obtained by the method for multi-point bending measurement of the composite material out-of-plane stiffness are used in finite element analysis and have high precision, test piece preparation is simple, the test method is simple, the accuracy of the data is improved, and the design cycle is shortened.

Description

technical field [0001] The invention relates to the technical field of aeronautical structure mechanics, in particular to a method for measuring out-of-plane stiffness of composite materials by multi-point bending. Background technique [0002] Material stiffness is the ability of a material to resist deformation when subjected to external forces, and is generally expressed by elastic modulus. Composite materials are anisotropic materials with varying stiffness in different material directions. According to the mechanics theory of composite materials, the flexibility matrix represented by engineering elastic constants is expressed as follows: [0003] [0004] The material properties can be characterized by 9 independent elastic constants, that is, the elastic modulus E1, E2, E3 in the three main directions of the material, the three Poisson's ratios γ12, γ13, γ23, and the shear elastic modulus G12 in the three planes , G13, G23. Among them, the elastic modulus E3 in t...

AI Technical Summary

Problems solved by technology

[0005] Existing methods for measuring out-of-plane stiffness (E3, G23, G13) of composite materials are only for individual items, and it is difficult to realize individual stress fields. The preparation of test pieces is complicated and demanding

Specific problems include: there is no official standard for the measurement of the out-of-plane tensile and compressive modulus E3, and the measurement method and the size of the test piece are still under further study; although there are ASTM formal standards for the out-of-plane shear modulus G23 and G13 , but the test method cannot realize the pure shear field, and there are other load coupling effects

[0006] The technical problem that needs to be solved urgently now is how to design a method for measuring the out-of-plane stiffness of composite materials, which can eliminate the coupling effects of each stiffness and solve the defects existing in the measurement of out-of-plane stiffness of composite materials in the prior art

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