Composites

Composites are materials that are made from two components, one of which is a matrix and the other a binder (often called the resin). The matrix is some sort of fiber, while the binder is typically some sort of epoxy resin. Fiberglass composite is made with fiberglass for the matrix and fiberglass resin as the binder.

The benefit of composites is that the combination of matrix and resin can create substances that have most of the good physical properties of both substances, and few or none of the poor physical properties. It is also common for composites to have additional good properties that neither of the original materials had. For instance, fiberglass resin by itself tends to be weak and brittle and fiberglass is extremely flexible and easily pulled apart. Together though, they create a strong, rigid, slightly flexible substance that is also fairly hard.

When making composites, you generally entirely soak the matrix in resin, then remove as much resin as possible. This minimizes the negative properties of the resin, while still effectively binding the matrix (the ratio of matrix to resin is sometimes used as a measure of quality of a composite). In industry this is often done using vacuum bags. (The composite is put into a large plastic bag, then the air and excess resin is vacuumed out.) In a post apocalyptic setting it will probably not be feasible to use a vacuum bag, even if you do happen to have the proper equipment. Instead, a tight fitting mold would work (one with two parts that compresses the material between the parts).

As an experiment, I am going to try using casein glue (see the previous post) with cotton or some other fiber that is commonly used in fabrics (I have to see what my wife has that she does not need). Since casein seems to bind well with cellulose (it was originally used as wood glue), cotton or some other natural fiber would probably be ideal. I think I actually have some scrap cotton around, so I'll use that for the first test.

Another common type of composite is wood laminates. (Look at the edge of a piece of plywood. Notice that it is made from several layers of wood glued together? This is a wood laminate. Plywood has several layers that alternate the grain direction, to make the sheet strong in all directions, instead of just directions that do not follow the grain.) In theory, casein would be a suitable glue for this as well, though probably not as good as the thermal epoxies commonly used now.