paintball pellets and inflatable articles from flexible (pvc-p) membrane

Ya know, the only preposterous part is your approach. Sometimes I just wana rip the slide-rule from engineers hands and knock them about the skull to encourage a reality check. Here's the empirical deal. Call up your client. Have him grab a paintball gun and meet you outside. Get one of your inflatables. Inflate it. Blast the hell outta the inflatable. See if it deflates. Have a few beers, roast some dogs, and then write your report. You'll have a great time and you can charge the whole afternoon to the R&D budget. Where is it written that every engineering solution must involve math?

You have 4 options.

1) Do as Dan says and examine the situation in a real time empirical test under a variety of actual ambient conditions and situations. This will require an extended test session so all your staff and friends can have fun as well. The material does not need to be made into a finished shape, just stretch some over a wooden frame and have fun. 2) Ask your client for more technical information which you require in order to assess the situation mathematically. You will need paint viscosity (probably thixotropic), paint surface tension and details of the exact shape of the paint ball at the time of impact. All of these will be required over a wide operating temperature range. Your client is very unlikely to have these details. You cannot give him an answer without these details so suggest 1) above. 3) Take your best guess that your product will work and tell him so. 4) do the same as 3) but add some complex looking data to back up your case. If the material does actually fail, tell the client that it was due to factors not revealed such as those in 2).

John