abstract：This article introduces two non-destructive testing techniques for carbon fiber composite materials based on ultrasound: AIRSCAN+air coupled ultrasonic non-destructive testing technology and PASCAN water immersed phased array C-scan ultrasonic testing technology. Imaging detection analysis was carried out for defects such as delamination, debonding, zone bending, and impact in resin based CFRP carbon fiber composite materials. By comparing the detection effects of two techniques for different defects, it was found that both methods can successfully detect various common defects in carbon fiber composite materials. Among them, AIRSCAN+air coupled ultrasound imaging detection technology is not limited by the thickness of the tested object, and various imaging methods can effectively detect and produce clear images. The PASCAN water immersion phased array C-scan imaging detection technology can not only detect various defects, but also quantitatively analyze the depth of defect burial. However, for thin plates below 3mm, high-frequency probes are required for effective detection.

keyword：CFRP, Carbon fiber composite materials, ultrasonic testing, air coupled ultrasound, water immersed phased array C-scan

background：With the increasing demand for lightweight materials and high-strength design in various industries, the application of carbon fiber composite materials is also becoming more widespread. Composite materials are made by combining carbon fiber with matrices such as resin, metal, ceramics, etc. Compared with traditional materials, carbon fiber composite materials have the following characteristics: designability and anisotropy, integration of material and structure, and dependence of material properties on composite processes. Carbon fiber composite materials have significant advantages in fields with strict requirements for density, stiffness, weight, fatigue characteristics, as well as in situations where high temperature and chemical stability are required. Therefore, carbon fiber composite materials have been widely used in transportation, aerospace industry, and other fields.

Although carbon fiber composite materials have been widely used as an emerging material, in the production process, due to unstable processes, defects such as voids and inclusions cannot be completely avoided. Its lateral load-bearing and shear resistance are low, and it is prone to damage and even failure under the action of impact or fatigue loads. Research has shown that the mechanical properties of carbon fiber composite materials change significantly with different sample thicknesses. Therefore, in order to ensure the tensile strength and elastic modulus of carbon fiber composite materials, it is necessary to strictly control the thickness of carbon fiber composite materials. With the increasingly widespread application of composite materials, there are more and more secondary mechanical processing, especially when assembling and connecting carbon fiber composite parts with other components. It is inevitable to perform a large number of hole processing, which can easily cause defects such as delamination in the composite material during the hole processing. Research has found that fiber orientation has a serious impact on the formation of drilling defects; The greater the axial force, the more severe the delamination defect, and the tear defect rapidly increases.

Common defects and causes of carbon fiber composite materials：

Experimental apparatus

AIRSCAN+Air Coupled Ultrasonic C-scan Imaging Detection System

Under the PASCAN water immersion phased array C-scan imaging detection system

[Sample]

Three types of samples were designed and produced based on the characteristics and common defect classification of ultrasonic non-destructive testing technology:

A: In the production of carbon fiber composite panels, artificial defects of different shapes and sizes are prefabricated to simulate layering, inclusions, pores, and debonding;

B: The intact carbon fiber board will be subjected to varying degrees of impact damage through hammer impact.

C: Multiple folds were prefabricated during the production of carbon fiber composite panels to simulate fiber zone bending and fracture;

【 Experimental Results 】

AIRSCAN imaging results of sample A (Part 1)

PASCAN imaging results (Part 2): Artificial layering, inclusions, pores, and debonding defects

AIRSCAN imaging results of sample B (Part 1)

PASCAN Imaging Results (Part 2) Artificial Impact Damage

AIRSCAN C-scan imaging results of sample B (Part 1)

PASCAN Full Focus B-scan Imaging Results (Part 2) Wrinkle Defects

Air coupling+photoacoustic imaging detection technology for detecting carbon fiber debonding defects (circular artificial debonding defects)

【 Summary 】

Both methods can detect various common defects in carbon fiber composite panels. The AIRSCAN air coupled ultrasound imaging technology has excellent imaging effects on various defects and can effectively detect carbon fiber boards of different thicknesses. PASCAN water immersion phased array C-scan imaging can effectively detect various defects and obtain depth localization information of defects. However, due to the problem of interface wave blind spots, there are technical difficulties for carbon fiber boards with a thickness below 3mm. It is necessary to further increase the probe frequency for detection or only consider using bottom wave imaging for detection. The combination of air coupled ultrasound and photoacoustic imaging detection technology also has a very good effect on detecting carbon fiber composite materials.

TECLAB provides various detection systems, sample preparation, and testing services as described in this article.