Igalla,

I can give you a couple examples that might help. A good composite does more than add up a bad one subtracts.

From boats. Solid fiberglass is very heavy so if you build a boat with fiberglass then you have to achieve a thickness that will give you the rigidity you need to keep it from tearing apart under repeated forces.

A wood boat is actually a bit better because of its cellular structure and density. You get greather thickness for less weight. Wood also has dimensional qualities which can be used to the boats advantage. It has the strength required for a tree stand straight. However wood requires more craftmanship and labor.

If you build a composite of wood with fiberglass skins of sufficient thickness than you can get the same characteristics of solid fiberglass and solid wood with less weight and moderately reduced thickness. The fiberglass provides direction reinforcement through the alignment of fibers and the glass provides tension under loads. The wood in this case is increasing thickness at lower density. Wood has good compressive strength for weight.

You can use honey comb, balsa, pvc foam to replace wood and reduce weight further. Of course then shear, fatigue, and delamination become more critical with PVC foam and honeycomb. With PVC foam a higher strength laminate reinforcement like carbon fiber can help in high speed applications. The epoxy formulation or similiar needs to be compatible with carbon fiber. The skin enhancement is because the PVC foam and honeycomb don't add as much to strength. The skin has to be stronger to compensate. The gain here is mostly a moderate reduction in weight.

compatibility of when a material will come into load strength versus another material is potentially an issue. If the fiberglass and epoxy in this example had lots of elongation before reaching top strength then the wood would carry much of the loading and fail without the stretchy fiberglass epoxy every really adding much.

There are also issues of dissimilarity including the natural frequency of oscillation of a particular material. Aluminum and carbon fiber are potentially disimilar enough to cause fatigue failure at connection points.

In my mind epoxy granite is an amorphous structure with no directional reinforcement so I wonder over time if it can become distorted.

So now you can see where my biases are derived from.


Anyhow thanks for the link that is very helpful.

Mike