This research focuses on the feasibility of airborne acoustics and acousto-ultrasonic techniques for inspection and characterisation of defects in composite structures.
The changes in the following inherent material properties of composite materials are harnessed for defect detection and characterisation in the composite structures.
1) Airborne Acoustic Technique (AAT)
AAT uses changes in the acoustic properties of composites with defect for defect identification and characterisation.
2) Acousto-Ultrasonic Technique (AUT)
AUT uses changes in the energy dissipation of stress wave caused by defects or damage in the composite material for defect identification and characterisation.
1) Test Samples
The test samples are generated taking into consideration different fibre architecture/matrix combination and various stacking sequences. In addition, conditions that result from constraint degradation due to mechanically induced damage are considered such as matrix cracking caused by cyclic loading, damage due to impact, cracking and impact damage combined, and simulated delamination.
There are several standard methods to measure acoustic properties of material. A common approach used is the ASTM E1050 which makes use of a plane wave impedance tube that is equipped with two microphones. The method evaluates material acoustic properties using the transfer function, between two microphones spaced a known distance apart, and at a given distance from test sample.
AUT provides a measurement procedure to quantify the integrated effect of the globally distributed damage characteristic for a fibre reinforced composite material. The procedure involves the introduction of a mechanical excitation into a test sample by means of a piezoelectric ultrasonic transducer and detecting the resulting disturbance at another point a short distance away on the same surface using an acoustic emission sensor.
Whereas conventional ultrasonic methods can be used to assess voids or other discontinuities, it falls short when the need arises to assess subtle flaws, such as is evident in composites with manufacturing-induced defects such as improper fibre/matrix distribution, ply waviness, wrinkle, porosity/void, foreign inclusions, incompletely cured matrix and improper fibre/resin ratio. AAT and AUT overcomes this limitation and can be used to access subtle flaws and associated mechanical properties variation in composites with defects. This research provides a novel approach of generating C-Scans for composites using AAT and AUT.
Unlike conventional acoustic emission monitoring which require the loading of the test piece for defect identification, AAT and AUT are passive techniques, can identify and characterise defects in an unloaded composite structure.
Application Web Page
Applicants must apply using the online form on the University Alliance website at https://unialliance.ac.uk/dta/cofund/how-to-apply/
. Full details of the programme, eligibility details and a list of available research projects can be seen at https://unialliance.ac.uk/dta/cofund/
The final deadline for application is 12 April 2019.