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Joint/Details

  • Large, singular panel adhered to 21 separate chassis tubes

    • 16 on the bottom

    • 3 on the catamaran section

    • 2 on the trunk section

  • Other than the trunk section chassis connections, the adhered length is relatively short

  • The bottom is completely fixed

Materials & Form

  • Chassis - 4130 Chromoly Steel - hollow tubes

  • Panel - Carbon Fibre Composite Sandwich - ~1.5” thick molded plane

    • AX-5201XL carbon fibre, NOMEX honeycomb, and corresponding adhesive film for carbon fibre

  • Adhesive - LOCTITE EA E-120HP - pasted and compressed between the panel and chassis

    • Epoxy-based

Material Characteristics & Notes

  • 4130 Chromoly Steel

    • Excellent strength-to-weight ratio

    • High tensile strength, ductility, and toughness

    • Lightweight in tubing form

      • In non-tubing form:

        • Modulus of Elasticity - 205 GPa

        • Ultimate Tensile Strength - 670 MPa

        • Tensile Yield Strength - 435 MPa

        • Rockwell B Hardness - 92

        • Elongation at Break - 25.5%

  • AX-5201XL Carbon Fiber

    • High stiffness, tensile strength, chemical resistance, and temperature tolerance

    • Low thermal expansion and weight-to-strength ratio

    • Excellent in tension

      • In general:

        • Modulus of Elasticity - ~230 GPa

        • Ultimate Tensile Strength - ~3.5 GPa

        • Tensile Yield Strength - ~2.1 GPa

    • Horrible in compression, but epoxy’s advantage in compression usually cancels that out when they form a composite

      • However, since we are by no means experts who manufacture our parts in a professional setting with quality equipment, I think we should lower our expectations when it comes to the material quality of not only our composites made with the Prepreg method, but the epoxy component specifically. I mean to say that the compressive counteraction that we look for in the carbon fibre composite, due to the epoxy’s presence, may not be expressed as strongly as we need it to be. Although, the NOMEX component might fix this issue.

  • NOMEX

    • High compressive strength, shear strength, materials compatibility, and fatigue strength

    • Low volume density and weight-to-strength ratio

    • High structural integrity

      • In general:

        • Ultimate Compressive Strength - ~2 MPa

        • Most other qualities change drastically based on stress direction

  • LOCTITE EA E-120HP

    • Superior thermal shock resistance

    • Excellent mechanical and electrical properties

      • Specifically peel and impact forces

      • Suitable for low stress [I wonder if that will be a problem.]

    • Withstands exposure to a wide variety of solvents and chemicals

    • Bonds dissimilar materials including aluminum, steel, and other metals, as well as a variety of plastics and ceramics

      • No mention of metal to organic compounds however

        • In general (for reinforced epoxy adhesives):

          • Modulus of Elasticity - ~4.5 GPa

          • Ultimate Tensile Strength - ~260 MPa

          • Tensile Yield Strength - ~230 MPa

Bonding Characteristics & Notes

  • Typical “Apply, Fix, and Cure” adhesive

  • Cavities may have been unfilled by the adhesive

    • Cavities created by part geometry or air bubbles created by uneven adhesive application

  • Clamped and cured for at least 24 hours

Known Forces or Stresses

  • General compressive stresses to chassis (and by extension the bottom panel) due to car parts placed on top (eg. seats)

    • Plus the external weight of the driver

    • Overloading a specific adhered tube may cause malformation and strain to the tube and adhesive, respectively

  • General weight of the bottom panel

    • We can test this if we get the approximate mass of the bottom panel

Potential Forces or Stresses

  • Any random stresses due to car functions (eg. the wheels being bumped into the bottom panel while turning)

  • Any random stresses due to the environment (eg. driving over a large rock the presses against the bottom panel)

Quality and/or Physical Concerns

  • Neither yet

    • The chassis hasn’t been adhered to the bottom panel as of right now (3:35 PM EST on Friday, July 9th), so no quality concerns

    • Still need to study and determine the experience of the bottom panel during car usage

Test(s)

  1. Max stress allowed (testing the adhesive here)

    1. Determine how much the adhesive can withstand

    2. Tensile, compressive, and shear stress must be tested

  2. General weight

    1. Determine safety factor and actual strain

    2. Needed: surface area, bottom panel mass

Testing Methods

  • MODS/Pre-calculations

  • SW

  • Physical

Expectations

Results

Analysis

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