7 Replies Latest reply on May 12, 2015 12:00 PM by Mark Ankrom

    Epoxy seam simulation

    Ben Ardwin

      Hi, I am interested in simulating a threaded seam that has been sealed with epoxy.  This system needs to survive submersion post drop test and we are trying to decide if our standard epoxy is sufficient or if going to a more flexible sealant will do the job for us.  In other simulation packages I was able to do this using beam elements generated between two surfaces to be sealed and then looking at the shear stresses generated but I haven't been able to figure out a method to do this in Solidworks yet.  Any suggestions?

       

      Thanks

      Ben

        • Re: Epoxy seam simulation
          Jared Conway

          why not just bond the 2 parts together and look at the shear stress between them?

           

          or model something in between them if you need the compliance/material props

           

          solidworks won't let you create a beam there because the gap would be too small

          • Re: Epoxy seam simulation
            Mark Ankrom

            Modeling bonds and sealer are usually a challenge because they are thin.  A plane Strain/stress or Axisymmetric model may be your best approach.

             

            Can you post a picture ?

              • Re: Epoxy seam simulation
                Ben Ardwin

                Here is an example of one of the thread interfaces I would be working with.  If anything the cavity from the counter-bore on the red part is a bit larger than I would normally need to deal with, and all of this would be part of a larger system that is being run through a drop simulation.  Typically the threads are sealed using an epoxy, but that seal has classically had trouble surviving a drop test so we are looking to see if changing to a more flexible seal will survive drop better.THREAD 1C.jpg

                  • Re: Epoxy seam simulation
                    Mark Ankrom

                    If this was anything but a drop, I would use an axisymmetric model for this problem. I haven't tried it but I suspect Solidworks does not support explicit dynamics with "planar" models.

                     

                    I did a lot of work on bond and composite failures due to statics, dynamics and pyro shock.  The basic rule is "Shock eats bonds".  The good news is that more ductile bonds like RTV survived much better than the brittle epoxies.  The key is to use bonds that have a high elongation to failure.  Hopefully all the loading is at well above the bonds glass transition temperature.

                     

                    Bond materials are all polymer based and the material properties change significantly with the rate of load application.  RTV's are best represented with hyperelastic properties and just the characterization of the material behavior for use in a shock problem is challenging.

                     

                    I suggest starting with something simple like a lap shear specimen.  If you can't analyze the lap shear then no sense wasting time on the real problem.

                     

                    If I was faced with this problem,  I would have some simple lap shear coupons built with the current epoxy and proposed "ductile" sealer and run some shock load tests to determine the relative improvement with the "ductile" bond.