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  • Users: cpinz
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  1. cpinz

    Radius Bridging Issue

    There are silicone plugs to use on edges in order to apply locally the pressure necessary to avoid fibre bridging.
  2. cpinz

    Resources for learning about aircraft structural design using composites?

    Take a look at Kassapoglou's books edited by Wiley Cpinz
  3. cpinz

    Shear Stress on Composite Beam (Divinycell + CFRP)

    It was noted that it's difficult ( referred to DIY structures of course... not for a commercial aircraft where it's common) to layup UD in the shear web... not in spar caps, where it would be preferable ( for the reasons explained above). Also for homebuilts to check for buckling is mandatory...
  4. cpinz

    Shear Stress on Composite Beam (Divinycell + CFRP)

    I think that the use of ud tape for caps is more appropriate than fabric. Uni- has no kinks as happens with warp and weft of fabric, so more alligned fiber, better fiber volume fraction and higher strenght. The value of E1=70 GPa that you cite, if referred to fabrics , seems too high. Anyway...
  5. cpinz

    Shear Stress on Composite Beam (Divinycell + CFRP)

    Maybe I will misunderstand again, but are you saying that the caps ( that is the section of the beam wich resists tension and compression), are made with woven fabric oriented at 0/90 along the spar axis ? The fact that you have different moduli in two direction doesn't explain why the cap's...
  6. cpinz

    Shear Stress on Composite Beam (Divinycell + CFRP)

    L.L = limit load U.L. = ultimate load = 1.5*L.L For composite construction additional safety factors must be taken in account based on surfaces color, and in case of static tests executed or not at high temperature. Therefore 150% could not be the ultimte load. It sounds strange that upper...
  7. cpinz

    Shear Stress on Composite Beam (Divinycell + CFRP)

    For a one-seat homebuilt, designed according to EAA,ASTM-LSA, BCAR, or LTF rules ( I strongly suggest you to take a look at them..), you will find that a conservative design ( from shear strenght viewpoint at ultimate load) for shear web of a wing supposed cantilever type, will give you 4 layers...
  8. cpinz

    Shear Stress on Composite Beam (Divinycell + CFRP)

    Hi, although your final application is not clear ( rc model, homebuilt airplane,...??) , SWcomposites's advice holds in general. Your spar web will be loaded in shear ( then +-45° fabric) and spar caps ( located where..?) will be loaded in tension/ compression. It's is good practice (...
  9. cpinz

    Resin Infusion Voids

    Never change temperature during infusion, start the process at the temperature held possibily constant at the value prescribed by the technical sheet (generally T>15°C ) Slow down the resin flow close to vacuum line placing the vacuum tubing at 50-60 mm from the laminate edge ( dont' place it...
  10. cpinz

    Vacuum Infusion: Increasing Fiber Volume Fraction

    What's that Soric for ? Is it intended as flow media ? If yes ,remove it. 6 layer can be easily infused with a normal flow media meshe available in different size an permeability.Of course your resin is intended for infusion and not for hand layup Then, starting from the mould: - mold release -...
  11. cpinz

    Torsional stiffness of rectangular plate

    SW, - I didn't use the fem to determine G modulus;I used it only to check the angle of torsion; I compared this value with that obtained from two hand calculation where I used the G moduli obtained from a66 (G_membranal)first and b66 (G_bending) then. -"you do not have a case of pure...
  12. cpinz

    Torsional stiffness of rectangular plate

    Hi Brian, thank you for your quick reply. I did the same, and I reached the same conclusion ( laminate is symmetric and balanced). After some hand calculation and some runs on ABD matrix, I run a simple case on fem; cross-checking all procedures I saw that, effectively, d66 terms influence G...
  13. cpinz

    Torsional stiffness of rectangular plate

    Hi all, a response to the following general problem would be appreciated very much. I have a rectangular plate made of n plies , its section is rectangular . Long edges aligned with x axis, short ones with y axis It is constrained (built in) at its left edge, free on other edges; pure torque...
  14. cpinz

    Carbon Fiber Fabrics 3k-135-8h

    RPstress, much appreciated your pointing out the errors of document. Thank you.
  15. cpinz

    Carbon Fiber Fabrics 3k-135-8h

    ...."Can someone advice me on the subject."... "Simple" request for a (very) difficult answer in one or more posts..! Just to start ...look at NASA Reference Publication 1351 titled " Basic mechanics of laminated composite plates"; you find it on internet. Hope it will be useful. Cpinz
  16. cpinz

    Composite Analysis And Testing in Aviation

    Hi all, -The failure from simple tension/compression test on unnotched specimen usually represents the starting point to further investigation on the failure of laminate. Then you should decide, on the basis of applications, if such tests are enough and reprentative of the real behaviour of...
  17. cpinz

    Composite Modeling

    Hi all, John84 forget FEM (for now).Take the time to read a textbook on the subject.If , later, you will find tedious to do some matrix calculation, use one of the many simple programs based on CLT; they will do for you what ESPcomposites explained in his posts above....but, before, "back to...
  18. cpinz

    Determining Elevator Stiffness

    I agree with SW about the need to make some hand calculation: - in this way you have something to use for a check of your fem analysis; - to apply rigid constraints on elevator ( moving part of horizontal tail) means that the stabilizer (fix part of horizonatl tail) is rigid too. But this, in...
  19. cpinz

    CF tuned exhaust for a racing RC plane

    There are ceramic based coatings usually applied in the firewalls of light composites airplanes. You can brush or spray them; check if your structure must be flame resistant or heat resistant. Regards Cpinz
  20. cpinz

    Wing Box Design

    Hi all, just curious.....which airplane has a wing with a span of 6.5 m and a chord of 13.5 m ?!! It seems to be a "big" airplane in a chordwise direction but not in the spanwise one

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