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A395 P10 Sumamary Notes - Coggle Diagram

- - - - • Damage within the composite should be located and extent of damage must be determined
        • Damage is negligible may be allowed to exist without repari as it does not affect the structural integrity of the component
        • Repairable damage are damages that needs repair and falls with the repair capability of the Aircraft Maintenance, Repair and Overhaul (MRO). [can be repaired on site or send to manufacture to be repaired]
        • Non-repairable damage are components that cannot be repaired and are discarded or scrapped.
- - - - Personal Protective Equipment such as respirator, downdraft table and vacuum are used
- - - - Done using a vacuum bag and heat blanket
        • Heat converts moisture into vapour and the vaccum draws the vapour out of the composite
  - - - Rapid increase in temperature and high temp drying causes delamination (temp increase should be low, never exceed 5 degree fahrenheit)
- - - - Eg. Titanium patches are used with carbon fibers as it does not cause galvanic corrosion and have similar strength and stiffness
  - - - Smaller load bearing area to transfer load to the fastener, resulting in bearing failure of the joint
  - - - Prevented by selecting correct bolt diameter and material
    - - Prevented by having sufficiently large bolts compared to the thickness of the joint (d/t must be greater or equal to 1)
    - - Prevented by having adequate edge distance and bolt pitch
- - - - The repair patch is made by replacing the plies that has been removed in damage removal and taper sanding
        
        The repair patch is cured to join the repair patch with the original composite
        
        Repair patch should be made out of the same material, orientation and stacking sequence as the original design
        
        Having the same material as the original in the repair shop is not practical
        
        SRM allows material substituition
        
        Consist of dry fabrics or prepregs
  - - - Perform taper sanding
        
        Taper sanding reveals individual plies in the laminate
        
        Prepare individual plies in repair patch
        
        Placement of the repair patch while taking note of the original plies orientation
        
        Vacuum bagging and curing
  - - - Flatter tapered angle (scarf angle) result in larger contact angle
      - Tapered angle (tapered distance per ply) specification is given by the SRM
        
        Recommended to taper sand 0.5 inch per ply of composite laminate
        
        Scarf angle
        
        Scarf angle = Scarf distance/Thickness of the laminate
  - - - When replacing the core, the ribbon direction should be taken note of (if applicable)
  - - - Damaged parts cannot be possible removed in the field
        
        Portable repair equipment (hot bonders) are used
        
        Hot bonders control the heat blanket which are placed over the repair patch within a vacuum bag to provide heat for curing
        
        Heat blanket ensures that the temperature of the repair patch is even
        
        Must be larger than the repair patch
        
        2 Inches at the edge of the heat blanket is colder (cold zone) as compared to the center
        
        Allows the thermocouple and composite to be within the hot zone
        
        Can be used for drying
        
        Thermocouples are used in conjuction with the hot bonders to measure the laminate temperature
        
        Temperature of the laminate needs to be control in a very precise manner as prepregs and elevated temperature wet lay up cures needs a specific cure cycle
        
        Produce laminate of opitmal quality
        
        • Temp too high: Turns off heat blanket
        • Temp too low: Turns on heat blanket
        
        Needs to be placed within the hot zone of the heat blanket
        
        When place within the cold zone, temperature will be underestimated, potentially causing a fire or damage to repair
- - - - • Thermocouple must be electrically insulated from and conductive surface (caul plate, carbon fiber)
        • Reason: Works via thermoelectric effect and records voltage across 2 different conductors. Fluctuations in temp reading can occur when in contact with conductive surface
        • Place two layer of flash tape on the surface in the shape of a cross first before securing the thermocouple with another layer on top of the first layer
        
        • Avoid unnecessary thermal insulation around thermocouples (very thick breather cloth)
        • Reason: Thermal insulation near or on the thermocouple cause it to heat up or cool down slower than the surrounding, resulting in an inaccurate temperature reading.
- - - - Makes the repaired structure stiffer as compared to the original and if the structure experiences significant flexural stress, failure may occur at the edges of repair
        
        Some repairs may be design purposefully to have lower strength to avoid failure at the edge