?url_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Adc&rft.relation=http%3A%2F%2Fmiis.maths.ox.ac.uk%2Fmiis%2F542%2F&rft.title=Non-monotonic+variation+of+stress+intensity+with+flaw+size+in+metal-lined+fibre-reinforced+pressure+vessels&rft.creator=Westbrook%2C+R.&rft.subject=Materials&rft.subject=Fluids&rft.description=Metal-lined+continuous+fibre+reinforced+plastic+(FRP)+over-wrapped+pressure+vessels+are+used+in+aerospace+applications%2C+for+storage+of+breathing+air+in+fire+fighting+and+scuba+diving+and+for+the+storage+of+compressed+gaseous+fuels+on+natural+gas+and+hydrogen+vehicles.+Continuous+fibres%2C+generally+about+15+micro+m+in+diameter+and+made+of+glass%2C+carbon+or+kevlar%2C+are+embedded+in+a+polymer+matrix.+The+metallic+liner+is+made+of+a+ductile+material+-+generally+steel+or+aluminum+alloy.%0D%0A%0D%0AAfter+the+metallic+liner+has+been+wrapped%2C+the+composite+vessel+is+subjected+to+a+process+termed+Autofrettage.+In+that+process+the+vessel+is+internally+pressurized+to+the+point+that+the+ductile+metal+liner+undergoes+a+small+amount+of+plastic+deformation+(unlike+elastic+deformation+which+disappears+upon+removal+of+stress%2C+plastic+deformation+remains+after+the+stress+has+been+removed).+Upon+de-pressurization+of+the+vessel%2C+the+metallic+liner+remains+under+compression+and+the+FRP+under+tension.%0D%0A%0D%0AAcoustic+emissions+associated+with+fiber+breakage+are+being+developed+currently+as+a+non-destructive+means+of+assessing+the+structural+integrity+of+metal-lined+continuous+FRP+over-wrapped+vessels.+Laboratory+experiments+have+been+carried+out+with+flaws+such+as+cracks+and+saw+cuts+of+varying+dimensions+oriented+in+an+axial-radial+plane+and+located+in+the+metallic+liner%2C+in+the+FRP+or+in+both.+Pressurization+of+the+flawed+vessel+leads+to+fiber+breakage%2C+the+extent+of+which+is+being+examined+with+the+intent+that+it+will+be+a+measure+of+structural+integrity+of+the+vessel.+The+results%2C+however%2C+suggest+that+the+acoustic+emissions+attain+a+maximum+for+an+intermediate+flaw+size.+Low+emissions+are+recorded+when+on+the+one+hand+the+vessel+has+insignificant+flaws%2C+or+on+the+other+if+the+vessel+has+serious+flaws.+This+non-monotonic+variation+of+acoustic+emission+occurs+whether+the+flaws+are+located+in+the+metallic+liner%2C+in+the+FRP+or+in+both.%0D%0A%0D%0AThe+experiments+suggest+that+the+stress+intensity+at+the+discontinuity+(crack+tip)+attains+a+maximum+at+an+intermediate+flaw+size.+A+mathematical+corroboration+is+desired.&rft.date=1997&rft.type=Study+Group+Report&rft.type=NonPeerReviewed&rft.format=application%2Fpdf&rft.language=en&rft.identifier=http%3A%2F%2Fmiis.maths.ox.ac.uk%2Fmiis%2F542%2F1%2Fnon-monotonic-variation-of-stress-intensity.pdf&rft.identifier=++Westbrook%2C+R.++(1997)+Non-monotonic+variation+of+stress+intensity+with+flaw+size+in+metal-lined+fibre-reinforced+pressure+vessels.++%5BStudy+Group+Report%5D+++++