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A395 P08 Summary Notes - Coggle Diagram

- - - - Design data
        
        • Strength of the material
        • Reliability of the material
      - Quality control
        
        • Feasibility of the produced part (design criteria)
        • Presence of defects in the material
      - Failure analysis
        
        • Why and how did the part fail
        • Improvement on the current design
      - Repair and maintainence
        
        • Presence of damages
        • Location of damage
      - Material property data
        
        • Tensile properties
        • Compressive properties
        • Shear properties
        • Flexural properties
        • Fiber volume fraction
      - Defects in composites
        
        Porosity
        
        Impact
        
        Moisture ingression
        
        Moisture ingression into honey comb
        
        Bolt hole design
        
        Wavy fibers
        
        Debonding
        
        Debonding of the skin and core
        
        Fiber misalignment
        
        Cracks and delamination
- - - - Matrix Ignition Loss Method
        
        Used for fiberglass only
      - Matrix Digestion Method
    - - Remaining residue containing the reinforcement is filtered, washed, dried (if needed), cooled and weighed
    - - • Vf is the volume fraction of fibers
        • Wf is the weight of fibers (g)
        • Wm is the weight of matrix (g)
        • ρf is the density of fibers (g/cm3)
        • ρm is the density of matrix (g/cm3)
  - - - Voids
        
        Large void in laminate
      - Ply count
      - Spatial distribution of the fibers and resin
      - Fiber waviness
      - Fiber orientation
        
        Laminate with woven plies
        
        Fiber waviness
        
        Laminate with unidirectional plies
      - Cracks
        
        Microcracks in laminate
    - - Sectioning
        • Reveal the plane of interest
        • Accomplished using diamond blade
        
        Mounting
        • To protect the sample and allow for easier handling
        • Sample is covered in resin
        • Clip can be used to hold small sample upright
        
        Grinding and polishing
        • To remove damage from sectioning and make surface smooth for examination
        • Grinding and polishing using different grit paper size and polishing cloths
  - - - Test for metals and plastic are not compatible for composites
        
        Large number of test are needed to fully characterize the material due to the anisotropic nature
      - • Specimen size and shape
        • Precautions to be taken
        • Test set up and apparatus
        • Specimen condition
        • Acceptable failure mode
        • Calculation and report
        
        Continuous fiber: flat, rectangular and straight edge
        
        Tabs (not necessary): prevent gripping damages, premature failure, enable distribution of loas to prevent build up of stress concentration
        
        Short beam shear test sample size
        • Span length = 4 thickness of the sample
        • Specimen length = thickness 6
        • Specimen width = thickness * 2
        • Minimum thickness = 2 mm
        
        Flexural test sample size
        • Standard specimen width = 13 mm
        • Span to thickness ratio = 32:1, 16:1, 20:1, 40:, 60:1
        • Specimen length = 20% longer than span length
    - - Short beam shear test
        
        Determine the interlaminar shear strength
        
        Beam used in short to minimize flexural stress and maximise shear stress
      - V notched beam test (Iosipescu)
        
        Test shear properties and in plane shear properties of composites
        
        Flat rectangular strip with central notches
        
        Shear stress is exerted on the notches
      - Compression after impact
        
        Measures the residual strength of the composite
        
        Inflict damage on the composite by dropping weight of known mass
        
        Test compressive strength of the composite using a special fixture to ensure stability of the laminate
  - - - Avoid delamination and rough surface
        
        Use water lubricated precision sawing, grinding with diamond tools
    - - Anisotropic nature of composite
    - - Adverse effect on mechanical properties
        
        Conditional chamber
        
        Condition specimen with controlled humidity and temperature during testing
        
        Environmental chamber
        
        Maintain the gage section of the test specimen at the required test environment
  - - - Occur at the gage section
    - - Failure between notches
    - - Pass through damage or through body of specimen
- - - - When the ultraasonic waves hits a defect, the sound wave is absorbed or reflected to the surface
        
        Reflected wave is picked up by a receiving transducecr and converted into a display on an oscilloscope or chart display
    - - Ultrasonic wave that hit the back of the specimen returns as an echo known as backwall echo
        
        Travel time of the defect echo is used to measure the depth of the defect from the surface
        
        Depth of defect crack = (time taken (defect echo)/2) x velocity of the sound
    - - DIsplace air and facilitates the transmisson of unltrasonic energy from the transducer into the sample
    - - Effective in finding non-parallel oriented flaws to the surface present
        
        Wedges are used to refract the sound beam at a different angle for detection of non-parallel flaws
        
        Used for straight beam probes and to protect the surface of the transducer from scratches and abrasion
      - Uses shear sound waves
    - - Obtain the correct velocity of sound within the material and wedge delay
      - Use reference blocks
        
        Made out of the same material as the test sample
    - - A scan
        
        Plot of signal amplitude against time
      - B scan
        
        Cross-sectional view of the scanned part
      - C scan
        
        Top view of the scanned part
    - - Involves 2 transducer
        • One to produce the sound wave
        • One to receive the sound wave
        
        The receivers are opposite of each others
      - Presence of defects between the transducers result in attenuation
        
        Attenuation: loss of ultrasonic energy due to reflection and absorption.
    - - Advantage
      - Disadvantage
  - - - Change in sound may be indicative of an underlying defects
        
        Common technique for detecting delamination and disbond
  - - - Heat sensing device is then used to measure the temperature variation
    - - Defect free areas are able to conduct heat more effciently as compared to defect areas
    - - Suitable for inspecting thin laminates and defects near the surface
        
        Deep flaws are difficult to detect
    - - Energy source is needed to produce thermal contrast within the material
    - - Thermal contrast occurs naturally
  - - - • One element transmit sound waves
        • One element receive sound waves