Expansion rate of Carbon Fiber vs Steel

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SUMMARY

The discussion focuses on the challenges of installing a carbon fiber roof on a Volkswagen Bug, particularly regarding the different expansion rates of carbon fiber and steel. The licensed auto body technician plans to fabricate an inner frame and achieve a flush seam with paint blending into the carbon fiber. Key to this process is understanding the coefficients of thermal expansion for both materials to prevent cracking or ghosting at the seam. The formula provided for calculating net growth is: Net Growth = (coeff exp metal - coeff exp carbon fiber) X Temperature Difference X Original Length.

PREREQUISITES
  • Understanding of coefficients of thermal expansion for materials
  • Knowledge of carbon fiber fabrication techniques
  • Experience with automotive bodywork and paint blending
  • Familiarity with structural bonding methods
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  • Research the coefficients of thermal expansion for carbon fiber and steel
  • Learn advanced carbon fiber fabrication techniques
  • Explore methods for achieving seamless paint blending on composite materials
  • Investigate structural bonding solutions for automotive applications
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Automotive body technicians, composite material fabricators, and professionals involved in custom vehicle modifications will benefit from this discussion.

Valhalla14
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I am a lisc. Auto body tech, and I have a customer who wants a Carbon Fiber roof on a Volkwagen bug, I can fabricate a inner frame, and bonding will not be an issue, (according to paint rep)

The hard part is I want to do a flush seem and have paint blend into carbon fiber. I will "butt" match it, and have it bonded on the back side where I can strengthen the bond, and on the outside I will do the standard procedure as a quarter panel

If the expansion rate is different I will experience cracking, maybe ghosting from the seam.

Is this something I could figure out, or just run from the Idea
 
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Yes, you could figure this out with the coefficients of thermal expansion of both materials:

Net Growth = (coeff exp metal - coeff exp carbon fiber) X Temperature Difference X Original Length

The temperature difference would be the maximum or minimum temperature in the area minus the temperature during assembly.

After you figure the expansion, you may be able to put a groove feature or something to accommodate this expansion.
 

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