3 Point bending Test of carbon fiber

- February 11, 2023 at 11:27 pm
  
  Rodrigo Barata Correia
  Subscriber
  
  Hi there,
  I have made a 3-point bending experimental test with a carbon fiber laminate but I don't know any of the elastic or mechanical properties of the carbon fiber that I have used.
  
  I have the force versus displacement curve, flexural modulus, and stress vs strain curve. All for a 3-point bending configuration.
  
  I've also done a 3-point bending simulation in Ansys with the generic 230 GPa woven carbon fiber but the results are way too off. Is there a way for me to extrapolate the properties of this carbon? Maybe changing the modulus of elasticity.
  
  I will leave a picture of the results I got experimentally and with Ansys.
- February 13, 2023 at 2:32 pm
  
  Sahil Sura
  Ansys Employee
  
  Hi Rodrigo Barata Correia,
  Please correct me if I'm misinterpreting the question,
  So you've performed a 3-point bending test on the sample (Sample A)of composite laminate (Of which you don't know any properties)
  You got data of force versus displacement curve, flexural modulus, stress vs strain curve, etc. for Sample A.
  
  Now you perform a 3 point bending simulation in Ansys but here you assign ' 230 GPa woven carbon fiber' material to the sample and get the results different.
  Now the question is how to model the material similar to Sample A in Ansys so that the results for the bending test are similar ?
  
  Is my interpretation of the question correct?
  
  If yes, there are following steps that might help you in solving the issue.
  
  First you might want to find out the grade of the carbon fiber and the epoxy used. From the data sheets of the material, you might get complete idea of individual fibers and matrix.
  With the use of 'Material Designer' in Ansys, you can create a representative volume element (RVE) of the laminate and simulate the same with the logged in data.
  This is an idealistic way to get a detailed simulation of the composite laminate.
  
  Other method can be, editing the pre-defined materials with the known values. You might want to duplicate any one of the materials present in the Ansys Material library closest to the one with the sample.
  Rename and Update the parameters of the new material. These parameters can be obtained through the physical testing of the samples.
  Once added, you can proceed with the same newly created material and check again the results comparing it with the test case.
  
  Also feel free to reach out again if any doubts faced.
  Please refer to the following resources to get more information on the same-
  https://ansyshelp.ansys.com/account/secured?returnurl=/Views/Secured/corp/v231/en/wb2_help/wb2h_EngDataapp.html?q=Engineering%20data
  https://ansyshelp.ansys.com/account/secured?returnurl=/Views/Secured/corp/v231/en/wb2_help/wb2h_MaterialDesigner.html?q=Material%20designer
  
  Hope this helps!
  Thanks,
  Sahil
  https://forum.ansys.com/forums/topic/how-to-access-the-ansys-online-help/
  https://forum.ansys.com/forums/topic/guidelines-for-posting-on-ansys-learning-forum/#latest
- February 13, 2023 at 10:40 pm
  
  Rodrigo Barata Correia
  Subscriber
  
  Hi there Sahil,
  
  Yes, you have described my problem perfectly.
  
  So far I've tried something like method 2 from what you have described, but I didn't get good results. I was thinking that if I just decreased the laminate's modulus of elasticity, the curve's slope of the force vs displacement plot would also decrease and I would get something more similar to my experimental results. What I got instead was a specimen that didn't endure almost any force.
  I will try method number one, but the best I can do is get the properties of the resin I've used. All I know from the carbon fiber is that it has an area mass of 30g/m^2 and it is biaxial+45º/-45º. Similar to the one in the following link
  
  Thank you,
  Rodrigo

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