Commentary about Cascade Engineering problems

Daina Fri, 26 Mar 2010:

I found a local expert on nano-clays. I won't name names, because unfortunately, I had a very difficult time getting across our idea of achieving integration of this problem/idea into the undergrad curriculum.  But this might work out anyway . . . .

A group of faculty have already been working on undergraduate education in nanotechnology. If you check out this web site (, it already contains a slew of educational information that can be used by freshmen through seniors.  ChE seniors already have a laboratory experiment in which they test the properties of various polymer films containing nano-clay particles. Apparently clays are very difficult to work with, so the experiments involve the students using pre-fabricated films with certain types of nano-clays already included.

The web site also has a simple simulation that demonstrates how a particular property (e.g., conductivity) changes with the amount of nano-clay loading in a polymer, in this case nylon, I think. So there is also something already for freshmen to do.

So the basic ideas behind the problem are

   * nanoclays can be exfoliated so that the "stacks" of clay are
     disaggregated; the state of disaggregation affects the physical
     properties of the composite
   * Cascade suggested using various energies to disaggregate the
     clays; apparently this is a false premise based on a "naive" (I"m
     quoting) interpretation of the mechanisms of how these clays are
   * This is an optimization problem: the properties of the composite
     are affected by the aspect ratio (length to width) of the clay
     particles in solution; different clays have different aspect
     ratios and thus give different properties
   * you can have good properties without all the particles being

I learned a lot, but now I'm tired of typing "disaggregated" so that's it for now! I'm not sure of what kinds of questions we can ask Cascade, because according to our resident expert, they are oversimplifying the problem in the wrong directions.

Daina Thu 04-01-10:

 If you are in the meeting and can read this message, here are a few
questions--haven't composed them into a formal set yet:

1. What is the objective of exfoliating the nano-clays?  What properties
are you trying to optimize?

2. Is 100% exfoliation desirable for this 'property' that you obtain from
the nano-clay suspension?

3. What is the trade-off between exfoliating and breaking the nano-clay

4. What would be the cost of obtaining nano-clays and suitable polymers to
run these experiments?  Are the virtual experiments or actual experiments
that you had in mind? Which nano-clays and which polymers? What type of
mixing equipment?

5. The energy of exfoliation also depends on the suspension density,
correct? Do you have suggestions for optimum concentrations to test?

These are just starters.

Tom Mon, 29 Mar 2010:

 I took a look at all three problems.

In each case, the general concept of the problem (why it is a problem) can be grasped, but in all three cases, students would need to have a governing set of equations, definitions of properties, etc. to define the problem.

I then Googled bio sand filters and the first link took me There is voluminous information here, but it didn't appear to be in a form where a student could take a set of governing equations and parameter values and build a model.

Then went to the Wikipedia entry, and at least quickly found a cross-section of one.

What is needed MAY be in the site, but there was so much there that the time to find what is needed to build a model for a homework problem would be disproportionate to building the model.

I see problems 1 and 3 in the same vein.

#1 Separating nanoclay layers -- how much energy is needed? Where would I go to get governing equations and parameters to model the separation process? Would those equations be mechanistic or empirical?

#3 Roof structures. This one could be worked by freshmen without Physics I or Statics IF you essentially gave them what they needed, and constrained the problem (e.g. defining the type of roof, where the load might be, etc.) Otherwise, they couldn't likely deal with point and distributed loads, moments and shear, bending stresses in beams, truss analysis (many real roofs are steel joist trusses), and they would need to avoid concrete or composite structures at all costs.

My thoughts on "authentic problems" for modeling remain the typical problems we often see in regular classes (they have stood the test of time), but represent REAL processes and products, and are not just made up numbers to put in equations. Statics books typically have many good examples, such as crane loadings.

My two cents.

Neeraj Wed Mar 30, 2010:

Comments on Problem 3

I agree with Tom that no Physics or Statics knowledge is needed.  This is a problem in bookeeping, i.e. making sure that all loads (dead, live, snow, wind.....) have been accounted for.  Depending on the roof type and material access to appropriate code or codes will need  to be given to the students.