A method for characterization of porosity of carbon fiber reinforced resin matrix composites based on ultrasonic dual parameters

Abstract

The invention relates to a carbon fiber reinforced resin matrix composite material void ratio characterization method based on an ultrasound two-parameter. The method belongs to the technical field ofnondestructive testing, and comprises the steps of adopting a set of void ratio detecting system comprising an ultrasonic fault detector, a direct contact type flat probe and a computer; acquiring amaterial parameter through a CFRP (Carbon Fiber Reinforced Plastics) mark to be detected, building a real morphology void model with a complex void morphology characteristic and a material property based on a random mediumtheory and a digital picture processing technique, building a relationship between void ratio P and an ultrasonic attenuation coefficient alpha sim through simulating calculationof a finite difference time domain software, and linearly fitting to obtain a P-alpha sim relational expression; selecting an area to be detected according to an ultrasonic C-scan result, adopting acontact type impulse reflection process to carry out multi-point acquisition on the selected area, and experimentally calculating alpha exp and an attenuation spectrum tilt K relevant to the void morphology characteristic; realizing CFRP void ratio characterization through the P-alpha sim relational expression and the K value. The method realizes CFRP void ratio characterization on the basis of considering the void morphology characteristic.

Description

technical field [0001] The invention relates to a method for characterizing the porosity of a carbon fiber reinforced resin matrix composite material (Carbon Fiber Reinforced Plastics, CFRP) based on ultrasonic dual parameters, which belongs to the technical field of nondestructive testing. Background technique [0002] Carbon fiber reinforced resin matrix composites (CFRP) have the advantages of high specific strength, high temperature resistance, and corrosion resistance, and are widely used in aerospace and other fields; since CFRP will inevitably produce pores during the production process, the existence of pores will directly lead to material The mechanical properties such as interlaminar shear strength, bending strength, and longitudinal / transverse tensile strength decrease, which seriously damages the service life of the material; the aerospace field usually requires the porosity of composite components to be below 2%, and some main load-bearing components Even the po...

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Problems solved by technology

[0002] Carbon fiber reinforced resin matrix composites (CFRP) have the advantages of high specific strength, high temperature resistance, and corrosion resistance, and are widely used in aerospace and other fields; since CFRP will inevitably produce pores during the production process, the existence of pores will directly lead to material The mechanical properties such as interlaminar shear strength, bending strength, and longitudinal / transverse tensile strength decrease, which seriously damages the service life of the material; the aerospace field usually requires the porosity of composite components to be below 2%, and some main load-bearing components Even the porosity is required to be lower than 1%; therefore, an accurate and reliable non-destructive testing method for CFRP porosity is urgently needed in engineering applications

[0003] Ultrasonic detection method has the advantages of wide application range, good directionality, high detection sensitivity, and harmless to human body. With the development of computer technology and automation technology, the accuracy and efficiency of ultrasonic detection have been greatly improved, and it has become the most commonly used method at present. According to the different ultrasonic parameters used, common CFRP porosity ultrasonic testing methods include sound velocity method, acoustic impedance method, attenuation method, etc. The sound velocity method requires a higher resolution detection system to distinguish the sound velocity The acoustic impedance method has high requirements for the accuracy of sound velocity and density measurement, which leads to the low applicability of the above method; the ultrasonic attenuation method has a clear detection principle, simple test technology, and is less affected by fiber content, which is currently the most concerned Porosity non-destructive testing method; this method starts from the time domain point of view, and uses the echo amplitude of the ultrasonic wave after passing through the CFRP sample to evaluate the porosity; however, it is affected by the experimental sample and pore morphology (pore size, shape, distribution, etc.) , for samples with the same porosity, the obtained ultrasonic attenuation coefficient values ​​are somewhat different; for samples with different porosities, the same ultrasonic attenuation coefficient value may also be obtained, resulting in a non-unique correspondence between porosity and ultrasonic attenuation coefficient; therefore , there are certain limitations in CFRP porosity evaluation using only time-domain signal amplitude

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