I have a set of three bending test data from CFRP composites. but I need to improve the strength and mechanical properties through hand layup, I have suggested RTM, but the problem is that the company should not pay for the device more. could you please help me with other suggestions?
Make sure you follow the following steps:
1. Blowing air using an air gun to remove dust (cleaning the fabric).
2. Make sure the total amount of resin/hardener is 1.5 times the fabric's weight (Total weight of resin = 1.5 x total weight of fabrics).
! always take an extra 20 gr for the waste.
!! An unproportionate amount of resin has an adverse effect.
3. Mixing your two-part epoxy resin (resin and hardener) for 10 min @ 100 rpm.
! Follow the spec sheet for the suggested mixing ratio.
4. Degassing for a sufficient amount of time depending on your resin/hardener gel (sand) time to remove most of the trapped air bubbles.
5. Apply the mixture on both sides of the fabric (unidirectional/biaxial CFRP fabrics) using a brush, in the hand-layup technique.
6. Meticulously, follow the manufacturer's spec sheet to start the curing process, and note that the curing process is different for cold- and hot-cure epoxy resins, e.g. a cold-cure thermoset epoxy resin, such as West System 105 resin and 206 hardener (Bay City, MI), needs to be cured at room temperature for at least 12 hours (higher strength can be achieved at the expense of allowing the curing process last longer), while a hot-cure epoxy resin, such as bisphenol-A based Araldite LY 1564 resin and Aradur 2954 cycloaliphatic polyamine hardener (Huntsman Co., West Point, GA, USA), requires to be cured in an oven at 60 C for 2 hrs and then at 120 C for 8 hrs, for the best strength and stiffness results.
As an alternative, try the vacuum resin infusion technique (VRIT) to remove the excess resin; or, replace the currently used epoxy resin with a stronger and stiffer one for the same price.
You're welcome!
With respect to VRIT, you probably forgot to clamp the resin (inlet) hose when the container's resin was completely consumed, resulting in air bubbles getting trapped inside the resin-injected fabrics; and at the same time closing the vacuum (outlet) hose to avoid unnecessary removal of the resin, leading to decrease the overall stiffness of the samples.
Good luck with your experiments!
I think that your samples need to post-cure according to the recommendation of the resin's manufacturer. This process can significantly improve the mechanical properties.
Dear Mahsa Amiri,
I hope you have solved the problem already. Prof. Soltannia and Dr. Najafi explained some solutions for the production process. I want to add some alternatives in case you still need.
1- You do not mension which oriantation angle carbon fiber or fabric used in manufacturing. If it is possible first and easy way to increase the mechanical properties to organize the orientation angle of the fiber reinforcement. Let say if you used unidirectional fabric, try to use 0/90 ( in order to increase the strength across the lateral loads) or if you used 0/90, try 0/+45/-45/90 (it makes quasi homogenous mechanical properties for the laminated coposite), and so on.
2- If 1st solution is not valid for your case, you can use a coupling agent in the matrix in order to increase fiber matrix interface bonding.
3- Similar to 2nd alternative, you can try the surface treatment for the carbon fiber before the lamination process.
2nd and 3rd solutions you can apply for hand-lay up, VARIM, RTM etc, is not depend on the composite production method.
Cheers,
Cemal
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