I’d originally designed and built this website in the summer of 2011, and I had made it a point that I myself did all the hard yards of learning the technology and developing (and finding how others had implemented a feature) the HTML and CSS code. I stayed completely away from Javascript, mostly because I basically had no idea about Javascript. I wasn’t sure how resource-hogging Javascript was, and that was a factor, yes—but it was mostly because I didn’t want to use something I didn’t know, and I knew next to nothing about Javascript.

So that was then.

For a while now, though, I’ve been pondering a rewrite and rebuilding of the website, for a number of reasons.

• The website was not responsive to different screen sizes. It had a certain minimum width that it required, and it always served the same webpage. In today’s world of smartphones and tablets, while it was passable, it wasn’t elegant by any means.

• As written, it was a pain to make changes to the website. I was dealing with separate HTML pages, and making any changes meant going in manually and make changes to every single page. Tedious, and prone to error.

  I needed a way to make a change once and have it propagate throughout all my HTML pages.

• I needed to consolidate my writing options. Let me elaborate, and let’s see how convoluted it gets.

  I already have my wordpress blog–GlobeTrekker–which I like and want to continue to maintain—not least because I have certain Google pagerank on there that I don’t want to lose.

  I had started a new blog, a self hosted wordpress blog, on this website, that I had planned would be a “science and technology” blog, separate from ‘everything else’ that I write at GlobeTrekker. But this blog was not the face, so to say, of my website.

  In trying to think of what I could/should write on my “home” page, I decided that I’d use that space to write tutorials about the stuff that I know best about—composite materials, health monitoring, and eventually, even transportation research that I work on at VTTI. I was very excited with this prospect, and managed to write three—count’em, three!—posts, in two years. (There was a reason for this, which I’ll come to.)

  The problem was that I was increasingly finding it inconvenient to write on either of my wordpress blogs. (The reasons for that are for another post altogether.) So I started yet another blog, hosted at Tumblr, that I’ve been using much more productively in the past few months.

  As you can probably start to guess, it was getting tedious and completely inefficient.

• There was a problem with trying to write tutorial posts (mentioned above) on my home page. The problem was, every time I wrote a new post, there was quite some amount of work neeeded to just post that new material. The previous post had to find a new webpage all to itself. This page had to have links to earlier and later posts. The new homepage had to add new links to the new webpage just created.

  On top of that, every time I did this, Google’s search results went crazy. People searched on Google and found links to my home page, but of course that old content was now at a new webpage. Bad for the person searching, bad for my Google pagerank.

  Tedious, cumbersome, inefficient.

  See a pattern here?

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So, in short—I needed some answers. And then recently, and finally, I stumbled upon Octopress.

In short, Octopress is a website building tool. It’s basically a Ruby program that does a number of things right out of the package.

• Assembles pieces of code to create the required webpages and support files to build an entire website. This straightaway solves my problem of having to make the same changes across all my pages. With Octopress, I make the changes in the one place where I need the change, and Octopress incorporates that change into all the web pages.

• Creates a blog, which is completely self-contained and self-hosted. Since it assembles everything locally, there’s no need for wordpress-style php pages on the server that handles collating pieces of content to serve a webpage.

  Octopress does it all, once, on my machine, and thereafter it’s just there, available for use.

• It provides a default theme of its own, but of course I am free to modify the code and designs as much or as little as I want.

  This is excellent, because now I can have all my web pages, including blog pages, with a consistent design. Getting this done with wordpress-hosted blogs is a pain, and while Tumblr is much better with this, it’s still infinitely more convenient to just have to do everything once.

  The website it creates is built to be responsive to different screen sizes. I’d been reading up on @media screen CSS usage, but having this built-in of course helped a lot.

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So here we are, with Octopress. What you see now is the result of the redesign and the rebuild. Here’s what has happened:

• The front page now hosts a blog. This single blog will host the mechanics tutorials that I had mentioned (see here), and also host other pieces that I will hopefully (and am planning to) write.
• The Tumblr remains the best place to share content that I find interesting on the internet, and I will continue using that, but mostly for sharing with the odd comment. I will try not to write longer pieces on Tumblr. However, I’ll probably cross-post whatever I write on this website on Tumblr, just to reach a wider audience.
• GlobeTrekker, of course, remains—with the same mission statement. I don’t know how frequently I will write there, though.
• The self hosted blog will be deprecated. I haven’t removed the files themselves yet, but the posts there have almost all been mirrorred on the new website, and I will remove the old files over time.

So that’s it. New website, new technologies.

And I’ve become much more comfortable with including Javascript on my website since before, now that I’m more confident that I know the basic HTML and CSS technologies well. There are some excellent specialized Javascript tools (such as the brilliant Modernizr and jQuery), that I’d be foolish to not use—and which Octopress, of course, uses out-of-the-box.

How do you like it? There still are improvements to be done, of course—and more of Octopress’s built-in code to be dug into, but that’ll happen over time. I’ve disabled comments for now to make for a cleaner interface, so please use twitter or email to respond.

Welcome to my new website—and happy surfing! :)

Stephen Colbert’s mother died, we learn, last week. Here’s him, giving a heart-warming, and heart-wrenching, eulogy to the woman who brought him up:

But even after the above, what struck me as even more exemplary is how he proceeds:

So, with that in mind… This… is the Colbert Report!

And the show, as always, must go on:

Condolences, Stephen.

Previously, we talked about what composite materials are, in an engineering sense. To recapitulate, composites are materials comprising two or more constituents. The constituents are combined in a way such that they retain their distinct identities in the final material (unlike alloys, for example). In particular, we talked about composites with a homogenous ‘matrix’ material (such as epoxy resin in polymer composites, and metals such as aluminum in metal matrix composites) in which reinforcing fibers (such as carbon fibers or glass fibers) or particulates are embedded. The fibers are the reinforcing material that provides strength to the composite, while the matrix material serves other purposes such as: (a) protecting the fibers (b) binding the fibers together to actually create the composite (c) helping to redistribute stresses if a fiber breaks.

But the key question is: why use composite materials at all? Why not use metals as always? What advantages do composites provide? Turns out, quite a few.

For one, composites are stronger than traditional industrial materials. How is strength measured? We all intuitively know this—by the amount of load that a material can withstand. Of course, for a fair comparison, the area over which the load (force, in technical parlance) is applied must be the same. (A thicker piece of wood carries more load than a thinner piece, but the wood itself remains the same strength; only the area of loading—the thickness, in this case—changes.)

A Mercedes-Benz bicycle that has a composite frame. (Source)

For another, most composites are lighter than their traditional counterparts. This is measured by density, which is the weight of the material per unit volume (just like we had considered constant area in the case of force, we must consider constant volume when considering weight). Like the example before, a larger piece of wood weighs more than a smaller piece, but the density of the wood itself remains the same.

Comparison of material properties, normalized by density. (Longer is better. Notice the metallic materials at bottom left.) (Source)

Combine the two traits—lighter and stronger—and what we get is a material that can withstand the same load with a smaller amount of material, and the material itself weighs less for the same volume! This is a pretty neat arrangement, no?

It doesn’t end there; this is just the beginning.

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Remember, most of the strength of a composite material comes from the fibers in the composite. Now consider a composite with all the fibers parallel to each other, i.e. pointing in the same direction. In which direction (or directions) does the composite have the most strength? Is it equally strong in all directions? Evidently not—the fibers provide tensile strength along its own direction, and so the composite itself will be much stronger in the ‘fiber direction’ as compared to other directions. We’ve discussed wood as an example before, and you’ll notice that the situation is very similar to this case of unidirectionally arranged fiber-reinforced composites.

Load on a table top: notice the fiber direction! Here the requirements are bending strength for the table top, and ability to transfer the load to the legs of the table. (Source)

Now that we’re comfortable with the idea of a unidirectional composite, consider this material as a building block. If you had a unidirectional material, that you could orient any way you like, and stack them so that the final material had fibers in multiple orientations, could you design a material to be strong in any direction you wanted? Certainly you could! And this is exactly what is done.

Composite Ply Layup. (Source)

And this brings us to the engineering and design side of composites. Even though, at first look, this seems like a dubious idea—isn’t it better that the things we make are equally strong in all directions? What if it breaks in one of the weaker directions?–this makes good engineering sense. Whenever a new component is designed, the designer has already figured out what the weak points of the structure are, and has already planned a way (or ways) that the component should fail, should it become overloaded or reaches the end of its life. In other words, a good engineering design factors in, during the design process, the directions that the component needs to be strong in, and the ways the material can and should fail.

Of course, this implies that the components perform at their best when they are used as intended. If a golfer strikes his golf club in frustration against a tree trunk, should he be surprised if his prized club goes out of shape? (On the other hand, if many golfers do this exact same thing, the designer of the hi-end golf club might take this into consideration when he makes a new design—but it probably will make the club even more expensive!)

A bent golf club, after it was struck against the ground. (Source)

And of course, what of the case where the component does actually need to be equally strong in all directions? Well, there’s nothing preventing the designer from using plies oriented in all directions, right? A component where the fibers are oriented so that the properties are approximately the same in all directions is called a quasi-isotropic material, i.e. a material that behaves sort of like an isotropic material, even though it actually isn’t.

A unidirectional and a quasi-isotropic laminate. (Source)

One final thing for this session. How to describe the ply sequence of composites? In brief (I’ll clarify as we come across actual examples), the most basic nomenclature is just a sequence of the play angles, with one of the fiber directions designated the ‘zero degree’ direction. Since it can get cumbersome to write the sequences of multi-layer composites (consider a 16-ply or 32-ply laminate, for example!), symmetries and repetitions in the order of the plies is used profitably. The subscript ‘S’ denotes symmetry, ‘N’ (where N is a number) denotes N repetitions of the same order, and ‘T’ conveys that no symmetries and repetitions are present (i.e. it is the ‘total’ sequence). Please see the figure below for some examples.

Composite stacking sequence nomenclature. (Source)

To summarize, the advantage of composites is first in its most basic properties—it is both stronger and lighter than traditional metallic materials. (It must be noted that this is a simple generalization; ‘strength’ can be of various kinds. For example, composites are usually not very good in compression). Further, composites can be engineered as per design requirements of each component. A basic unidirectional building block can be used to prepare composites with a variety of effective material properties.

In the broadest sense, a composite material is one that consists of two or more distinct materials—which retain their individual properties even when the final material is formed! In fact, we’ve all encountered various composite materials in our everyday lives.

Aggregate Concrete. (Source)

Take concrete, for example. Have you ever seen concrete being made for construction? It comprises cement (which binds everything together) and many other materials, including crushed stones. The properties of concrete are a combination of the properties of everything that went into it. Moreover, if concrete in its finished form is seen under the microscope, one finds that the components are essentially “mixed in”, and don’t interact chemically with each other in any way.

(This is, in contrast, to things such as alloys. Alloys, for example, are also made of multiple components—mostly metals, sometimes nonmetals such as carbon—but the final product has vastly different properties than the constituent materials. Also, the components themselves interact with each other at the smallest scale, and are not simply “mixed together”.)

Plywood is another example of a common composite material. In this case, you don’t even need a microscope: the individual layers making up the plywood are evident quite easily! In fact, while we’re on plywood, let’s remember the word ply—it refers to each layer of wood that makes up the plywood (yes, that’s how it gets its name). We’ll use the word ply plenty times later on.

Plywood. (Source)

Okay, so that’s what composites are in the broadest sense.

But in an engineering and research perspective, a “composite” is something more specific. To wit, a composite material is an engineered material, in which one or more heterogenous components are used as reinforcement in a matrix of homogeneous material. If the material used as a matrix is a metal, it’s called a Metal Matrix Composite (MMC).

Okay, so let’s break that last paragraph up a little bit. First, the “matrix of homogeneous material”. This refers to any material that’s uniform (like cloth, gauze), which serves as the base for your composite, and between layers of which—or even into which—you can embed other things if you wanted to. (In concrete, the cement can be thought of as the matrix, into which you can add other things—including steel rods to create reinforced concrete!)

Reinforced Concrete. (Source)

As I already said, if the matrix material is a metal, the composite is called an MMC. But a variety of other materials are also used as the matrix material—different kinds of polymers, usually. The most popular one that I’ve come across is epoxy resin, but other than that, vinylester or polyesters are also used.

The reinforcing material in the composite is usually either a fiber (more common) or a particulate material (less common). Since fiber-reinforced polymers are more common—and what I mostly work with—let’s talk about fibers a little bit.

Fracture surface of a SiC fibre-reinforced Cu metal matrix composite. (Source)

Fibers are a source of strength in composites, and a number of different kinds of fibers are used. Most common are carbon fibers, glass fibers, or even boron fibers. The question, of course, is—if the fibers add strength, why not build the entire material out of the same material as the fiber? Well, due to the way materials are manufactured, larger the size of the building block (i.e. the smallest unit used over and over again), lower is the overall strength. Hence, for example carbon in fiber form is much, much stronger than carbon in, say, sheet form (interested readers should look up “carbon fiber whiskers”–I could not find appropriate web pages to link to). This is why fibers are used for strength, and other materials (the matrix) are used to hold everything together around the fiber. (One can think of Metal Matrix Composites as special cases where even the matrix needs to be strong in its own right.)

Thus, to summarize, a composite material usually comprises a homogeneous matrix material, in which certain fibers are embedded to add strength and other advantages to the material. In some cases the matrix can be a metal, in which case the overall material is even stronger.

Let us get introduced, first, to a class of materials which are highly directional in nature. What does directional mean? Let me give an example. Imagine that you have a sheet of thermocol in your hand. Try to pull the sheet apart—if it’s thin enough, you probably can. Does it matter in what direction you hold the sheet of thermocol? Top-bottom versus left-right? Of course it doesn’t. This is an example of a material that is not directional—it responds in identical fashion, whichever direction you choose to interact with it in.

Thermocol Sheets. (Source)

Now consider a log of wood. Have you seen pieces of wood closely? Have you noticed the striations that seem to run along the length of long pieces or logs of wood? Those are natural fibers present in the wood, and they provide the wood extremely high strength on the direction of the fibers. It’s pretty hard to cut wood across those fibers, and wherever possible, wood is cut along those striations.

Wood Grain. (Source)

Wood, then, is an example of a material that’s directional—its response to external effects (such as a saw cutting through it) differs along different directions. That brings us to our first set of technical terms: isotropy and anisotropy. The thermocol sheet (or Aluminum, or Steel, or most other metals) is not directional—it’s isotropic. Wood is directional—and is anisotropic.

Why is this important? Because composite materials gain significance in large part because they’re anisotropic! Which means, they’re strong in one direction; not-so-strong in another. Plus, they can be engineered to be strong in any direction you want!