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Mechanical Testing of Composite Materials

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Tube Stock

Inserts interfaced with Carbon Fiber Tube

Things to test

• Mechanical Tests

  • Tensile Test- needed for plug

    • How to test it

    • Probably not needed since the push rod will be under constant compression

  • Flexural Test

    • three-point and four-point bend testing according to ISO 14,125, ISO 178, ASTM D 790, and ASTM D 6272

    • parameters for this test are the support span, the speed of the loading, and the maximum deflection for the test

  • Impact Test

  • Compression Test

    • End loading

    • Sheer loading

    • ASTM D 695, ASTM D 3410, and ISO 14,126.

    • information on elastic limit, proportional limit, yield point, yield strength, and compressive strength

• Strength at high temperatures (Summer)

• Fatigue Failure?

Plug Testing

• Adhesive

  • Loctite

    • EA E-40HT

    • DP420

    • DP460

    • Hysol E‐120HP

• Tube and metal prep

  • Aluminum etching and Alodine coating to prevent corrosion and increase bond strength

    • West  System 860 Aluminum Etching Kit

    • DuPont Acid Etch and  Alodine solutions

  • Submerge Aluminum in etch solution, then submerge in non-diluted Alodine solution

• Aluminum stock for insert

  • Check for appropriate lengths

    • Bond length increases linearly with bond strength

  • Gap 0.004 - 0.012 in for hot bonding

  • Gap 0.008 in for cold bonding

  • Carved aluminum, tapped for fitting a bearing insert

  • create shoulder only for grabbing in tensile test

  • In MIT paper, flashbreaker tape was used to add thickness at the end of the insert to create equal spacing and center insert.

Process for Insert Tensile Test

1. Create Aluminum inserts

   1. 0.004-0.012 in gap

   2. Leave shoulder length for Instron machine to grab

   3. Have a length of about [some] inches that will adhere to the inside of tube

2. Cut the Carbon Fiber tubes into about 3-5 inch sections

   1. The tubes are 5 feet long, so we can get at least 12 tests from one tube

3. Prep the surfaces

   1. The aluminum inserts will be sanded, degreased, submerged in etch solution for 3 minutes, then submerged in non-diluted Alodine solution

   2. The CF inner part will just be sanded and degreased

4. Add Epoxy

   1. We may test mixing the epoxy with small glass beads to properly center the insert, or use of Flashbreaker tape

   2. Slather chosen epoxy on the insert and inner part of CF tube

5. Insertion

   1. Slowly push insert into tube and let cure for 24 hours.

6. Testing

   1. After putting the insert into both sides of the tube, attach to Instron machine

   2. Pull until failure

ASTM D 695 (compression test)

• What is being recorded: Used to find the modulus of elasticity, yield stress, deformation beyond the yield point, and compressive strength 

• Procedure: ASTM D695 Rigid Plastic Compression Testing

• Machinery Used: Can be performed on either a single-column or dual-column universal testing machine such as those available in Instron's 3400 and 6800 Series (ASTM D695 Compression Testing Rigid Plastics)

ASTM D 3410 

• What is being recorded: Used to measure the ultimate compressive strain, the compressive modulus of elasticity, Poisson’s ratio, and transition strain.

• Machine used: Standard Universal Testing Machine

• Procedure: ASTM D3410 Polymer Matrix Composite Shear Load Testing - ADMET (testing procedure tab)

ISO 14,126.

• What is being recorded: the compressive strength and compressive modulus of fiber-reinforced plastic composites in the in-plane direction, meaning the direction parallel to the plane of the laminate

• Machinery Used: ISO 14126 | ASTM D3410: Shear Loading Compression

• Procedure: In-Plane Compressive Properties of Fiber-Reinforced Plastic Composites