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Dubai

Skin-core Debonding In Resin-infused Sandwich Structures

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Published in: Networking
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Presented at the 12th International conference on Flow Processes in Composite Materials (FPCM12) Location: Netherlands (2014) Topic Presented: Investigation of Skin-Core Adhesion in Resin Infused Sandwich Panels.

Hassan J / Dubai

8 years of teaching experience

Qualification: PhD

Teaches: Mental Maths, Mathematics, Physics, Engineering, Aeronautical Engineering, GMAT

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  1. KHALIFA UNIVERSITY PhD Project: Skin-core Debonding in Resin-infused Sandwich Structures Hassan Jishi Supervisors: Assistant Professor: Professor: Khalifa University June 17th 2014 Rehan Umer Wesley J. Cantwell
  2. Introduction Sandwich panel manufactured from low density core materials and composite skins yield lightweight structure, which is both strong and stiff. Single Skin -t SVeight: Strength: Stiffness: Sandwich — 2! Weight: Strength: Stiffness: 12 Sandwich — 4! SVeight: Strength: Stiffness: 48 [1] One particular area that is attracting significant interest relates to the design and manufacture of lightweight wind turbine blades for use in the energy-generation sector. [2]
  3. Motivation Skin-core debonding is a common and potentially catastrophic failure mode tha is frequently observed in statically and dynamically-loaded sandwich structures. Skin Core Driving down cost with much interest being centered on liquid molding techniques, such as vacuum assisted resin transfer molding (VARTM). Holes are drilled through the core, facilitating the movement of the resin flow front from one skin to the other. 3
  4. Objective Investigate techniques for enhancing the interfacial fracture properties of sandwich structures based on a brittle PET foam. Perforations introduced into the PET foam to enhance resin flow during the VARTM process, are reinforced with glass fibers in a bid to enhance the skin-core fracture properties The fracture properties of these reinforced foams are compared to those offered by a plain PET foam as well as cores containing resin-filled perforations. 4
  5. Materials Core Material: Polyethylene-Terephthalate (PET) Nominal density: Thickness: 130 g/mm3 20mm Reinforcing Skin: Unidirectional E-glass fabric Areal density: Number of layers: 600 g/m2 4 Resin System: Epoxy (Prime 20LV) with a fast hardener Weight mix ration: 100 Resin : 26 Hardener Geltime: 30 minutes @ 250C 5
  6. Pre-crack l) Material A Pre-crack 2) Material B Pre-crack 3) Material C Pre-crack 4) Material D-S and D-D Pre-crack 5) Material E-S and E-D Pre-crack 6) Material F-S and F-D Manufacturing Tests were undertaken on the six types of sandwich structure: Plain foam core. Perforated foam core with holes arranged in a 25.4 mm and 12.7mm square pattern. Perforated foam core with holes reinforced with glass fiber tows arranged in a 25.4 mm and 12.7 mm square pattern: Fiber volume fraction 0101.5 and %3 Continuous fiber tow and individual
  7. 6/13/2016
  8. 8 7 6 5 4 3 2 1 VARTM Manufacturing Technique After laying the dry fiber preform, foam core and distribution medium and vacuum bagging the assembly, vacuum is pulled at the exit to infuse the preform. Resin flow direction Vacuum pump Resin tra I Release coated mold 2 Sealant tape @ Vacuum bagging film 4 Core 5 Pre-crack (O Skin 7 Peal ply @ Flow media Resin reservoir 8
  9. VARTM Manufacturing Technique Flow front progression during infusion: (a) Top face sheet with in-plane flow. (b) Bottom Face Sheet with in-plane and radial through the holes from top to bottom. (a) (b)
  10. Compression Tests and Results Square specimens with a edge length of 50 mm were compressed between two circular steel plattens at a crosshead displacement rate of 5 mm/min. Fiber-reinforced perforations served to increase the compression strength of the foam. D-S Material E-S F-S 10
  11. Interfacial Fracture Tests Schematic of the three point bend test used to characterize the interfacial fracture toughness of the sandwich structures. The core and the lower skin directly under the pre-crack were removed. The crosshead displacement rate was set at 2 mm/min. Pre-crack (20.0) d Load o Skin Core d 11
  12. Interfacial Fracture Tests Results Plain cores offer an average fracture energy of approximately 675 J/m2 Maximum benefits gained from spreading the firbers across the top and bottom surfaces (samples F-S and F-D). 3000 2500 2000 1500 1000 500 A B c D-S E-S Material F-S 12
  13. Conclusion Presence of the resin-filled perforations increased the compression strength of the core. The presence of the through-thickness fibers served to act as bridges that arrested and subsequently stabilized the crack. Introducing small amounts of glass fibre through the core resulted in a 300% increase in interfacial fracture toughness. 13
  14. Thank you Questions References [1] Sandwich Principle Page. http://www.mech.utah.edu/senior design/05/index.php/HSUAV/SandwichPrinciplePage [2] Offshore Wind Turbine News. http://www.offshorewind.biz/

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