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Investigation of the Phased Array Ultrasonic Inspection on Uni‑Directional and Woven Carbon Fibre Composites

Project Code: 0901-11

Objectives

Determine the requirements and feasibility of using an angle beam inspection method to carry out phased array UT single sided inspection of composite components.

Investigate the ultrasonic beam distortion and beam bending due to the composite microstructure.

Derive a methodology for procedure development for single sided phased array UT inspection of complex geometry composite structure.

Project Outline

The project will have the following key stages:

Procurement of samples. A minimum of ten samples will be required having two common layup patterns and three thicknesses.

Carry out experimental work using immersion UT and conventional probes to determine beam bending and distortion characteristics at a range of angles.

Using the knowledge gained, develop focal laws required for pitch catch inspection using a single phased array probe.

Carry out phased array technique development and trials.

Develop a specimen UT procedure for single sided phased array angle beam inspection of composite structure.

A minimum of 10 samples will be sourced from member companies. A range of thicknesses up to 100mm will be used and a number of common weave types, one simple, virtually unidirectional layup and other 90/+45/0/-45 or similar common layups. The through thickness and longitudinal material velocities will be determined in order to calculate the theoretical incidence angles into the samples.

The initial immersion UT experiments will focus on through transmission using conventional transducers. A single fixed transducer will transmit a longitudinal beam at a specified angle into the component. A second immersion probe will be used to produce a raster scan of the back surface of the component to detect the emergent sound beam and determine its position. A variation of this experiment also to be trialled is the use a fixed phased array probe as the receiver as shown in Figure1. By using this approach, the theoretical and actual positions of the ultrasonic beam at the backwall will be determined. Several scans will be performed, using a range of angles between normal incidence and the first critical angle. This effect is not expected to be linear. The resulting data will be used to generate characteristic curves for a range of angles and materials and a relationship will be sought.

Using the derived relationship will allow the specification of a phased array probe capable of pitch catch operation and the calculation of the required focal laws to generate the angle beams and capture data. Simulation software will be used to verify the ability of the probe design to generate the ultrasonic beams before committing to manufacture.

Trials will then be undertaken both in immersion and contact modes to determine the accuracy and effectiveness of the developed technique and the proposed methodology for procedure development will be documented.

Relevant Industry Sectors

Aerospace

Technical and Economic Benefits

Will allow TWI to increase its market share for inspection of these normally difficult materials.

Will allow members to meet production quality and throughput requirements through fast, reliable inspection of complex geometry composite components where no current inspection method exists.

The results from this project will pave the way for SCP and GSP work aimed at client or application specific materials and structures.

This project will form the basis of further study into tomographic UT inspection of composites.

For more information please email:


contactus@twi.co.uk