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Composites Ultrasonic Testing (UT) & Quality Control for Aerospace at MWIP

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Introduction to Ultrasonic Testing of Composites for Aerospace

Ultrasonic Testing (UT) is one of the most effective Non-Destructive Testing (NDT) methods for detecting and measuring internal flaws. UT is widely used for testing composites in aerospace applications. Depending on the quality requirements and volume of testing, ultrasonic testing of composites can be performed manually or through automated methods.

Flaws in Aerospace Composite Materials

Common flaws observed in aerospace composites include voids, delaminations, porosity, ply gaps, disbond or debond, foreign materials, and inclusions. Composites are well-suited for UT, using either pulse-echo from one side of the material or through-transmission when both sides are accessible.

Ultrasonic testing of composites is most effective in detecting flaws perpendicular to the ultrasonic beam. Delaminations and debonds are easily identifiable through this method. While angle beam shear waves can be used, straight beam UT is more commonly preferred. Additionally, dry scan testing is a preferred approach, as the use of couplant may lead to seepage into the composite material, potentially causing damage.

UT Technique for Composite Ultrasonic Testing

The pulse-echo through-transmission technique employs straight beam longitudinal waves for both transmission and reception. Since aerospace composites are highly heterogeneous, selecting the appropriate frequency is crucial for achieving the desired sensitivity. Typically, ultrasonic testing of composites is performed using frequencies ranging from 500 kHz to 15 MHz.

For aerospace composites, the Back Wall Echo (BWE) method is widely used for sensitivity establishment. Although Distance Gain Size (DGS) curves are also useful, the practicality of BWE makes it the preferred approach. Identifying and sizing flaws is crucial for determining composite acceptance, and continuous monitoring of BWE loss throughout the scan is necessary, as a significant loss may indicate a serious defect.

Procedure for UT of Composite Material & Quality Control Measures

To ensure testing quality, proper overlap during scanning is essential. Generally, a 15% probe overlap is sufficient for ultrasonic scanning of composite surfaces. In the pulse-echo technique, fluctuations in back wall echo amplitude must be noted, and significant losses should be recorded.

For flaws larger than the probe size, the 6dB drop technique is commonly used to estimate flaw dimensions by marking probe positions. Flaw acceptance is then evaluated as per established standards. In addition to flaw detection, Quality Control (QC) measures must be integrated to ensure compliance with industry standards, minimize errors, and maintain consistency in aerospace component testing.

Aerospace NDT & Quality Control Services at MWIP Bhopal, India

MWIP’s Aerospace NDT Division specializes in dry-scan through-transmission ultrasonic testing of aerospace composites. Each UT Level 2 inspector at MWIP has extensive experience in aerospace testing applications. The institute also provides comprehensive training and certification for Ultrasonic Testing Level 2 at Make World Institute of Petroleum (MWIP).

MWIP’s NDT and Quality Control services in Bhopal,India, are ASNT accredited and include the following aerospace NDT testingmethods:

• Magnetic Particle Inspection (MPI) – Testing of aerospace hardware
• Fluorescent Penetrant Testing (FPI) – Inspection of aerospace components
• Quality Control and Inspection Techniques – Ensuring defect-free composite structures
• Industrial Quality Assurance Practices – Implementation of rigorous aerospace QC methodologies
• Advanced Quality Management Systems – Maintaining industry-standard compliance in aerospace NDT