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15 Cards in this Set
- Front
- Back
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!! What are the four stage of Quality Assurance?!! |
- Quality control of raw materials - Monitoring of manufacturing process - Quality assurance of finished product - Damage monitoring of in-service part Page 9-2 |
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What is tested when performing quality control of fibres? |
- Testing is done on single fibres, multi filament yarns, impregnated strands or fabric material - Properties tested include longitudinal tensile strength, elastic modulus, elongation, yield, density, twist, creep and sizing content Page 9-3 |
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What are important considerations for the quality control of resins? |
- Mechanical properties are determined by the gel time and viscosity (gel is defined as when the resin strings breaks sharply when probed and string) - Tests are performed on individual ingredients or mixtures as well as on the final blend Page 9-5 |
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What testing is done on cured laminates? |
- Physical tests -> for thickness, defects, GTT - Mechanical tests -> tensile, compressive strengths, tensile moduli and poisson's ratios Page 9-7 |
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What are the aspects of process control in terms of producing composites? |
- Material control: control quality of materials used - Control of environment: T, humidity, dust, etc. - Equipment is working properly: Vacuum pumps, hot press, etc - Control of tooling and moulds used - Control of Pre-fab process (cutting and lay up) - Control of cure process: temp, pressure, heating and cooling rate Page 9-8 |
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How is the final product assessed for quality? |
- Checking dimensional tolerance, physical inspection, Non Destructive inspection, mechanical and destructive tests if necessary Page 9-9 |
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!! How is the cure monitored for composites? !! |
- Cure monitoring is essential for thermosets - Need rigid adherence to pre-defined temperature and pressure - Autoclave and RTM processes can be optimised by using sensors in a feedback loop to fine tune the application of pressure temperature and vacuum - most common way is to place a thermocouple at different locations along the component - measuring electrical properties can be correlated to the degree of cure (viscosity is inversely propotional to conductivity) Page 9-10, Page 9-11 |
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What are the three categories to characterise damage in composites? |
- Fibre breakage - Matrix Cracks - Delaminations Major source of damage is impacts Page 9-17 |
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What are the two main techniques used today to inspect aircraft composites? |
- Radiography - Ultrasonics Page 9-20 |
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What is the difference between pulse echo and through transmission technique for fault inspection? |
- Pulse echo, the same transducer is used as a sensor to send and receive the signal - Through transmission - the transmitted signal is read by a second transducer Page 9-21, Page 9-23 |
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How does ultrasonic testing work and what is it good for finding? |
- It works by detecting voids or delaminations, which will cause a significant discontinuity in acoustic impedance. - It is good for finding defects perpendicular to the direction of the pulse, such as delaminations. Page 9-21 |
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What is an A-scan and a C-scan? |
A-scan - Ultrasonic testing - point scan for finding localised faults in the field, may require a coupling medium such as a gel because of the poor acoustic impedance of air C-scan - 2D scan over a large area using automatic traversing probes, often using immersion tanks Page 9-22 |
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How does radiography work? What defects does it find? |
- Level of x-ray absorption depends on material density. - A defect will have a different density and show up on the x-ray film - Not great for planar defects, but good for finding faults parallel to the pulse direction Page 9-28 |
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How does thermography work? |
- Thermography involves detecting variations in the surface temperature of components due to the presence of moisture, dis-bonds, cracking, etc. - Active thermography involves using pulse heating, while passive thermography involves nothing else Page 9-34 |
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How does the acoustic emission method find defects in a composite? |
The acoustic emission method involves monitoring the sound released from a component after sound waves (or an object) hit it. The tester knows what response they should get. Page 9-40 |
