Revision 1. 6
1.7
General
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1.3 Fiber Composite Basics
Plastics in General
For thousands of years human existence depended on natural materials. Clothing, tools, and utensils
were made from leather, metal, stone, clay and other substances provided by nature.
Most manmade materials like porcelain, glass, and metal alloys were discovered more or less by
accident.
When important raw materials started to become scarce and expensive at the beginning of the 20th
century, an intensive search for synthetic (artificial) substitutes ensued. Natural materials alone could
no longer satisfy the emerging technical requirements of the fast-growing industries.
In the course of time a myriad of compounds, including numerous plastics, were synthesized from
natural raw materials such as coal, coal tar, crude oil, and natural gas.
Combining different materials to form a composite with enhanced properties and synergies is a
common process in nature: the section of a strand of merino wool or a bamboo stem shows
structures similar to the cross section of a unidirectional carbon fiber reinforced epoxy resin (CF-
EP). Nature remains the model not only for the microstructure of fiber reinforced plastics, but also
for the application of lightweight design principles.
The use of fibers as construction materials is based on the following four paradoxes of materials:
1. The Paradox of the Solid Material
The actual strength of a solid material is much lower than its calculated theoretical strength (F.
Zwicky).
2. The Paradox of Fiber Form
The strength of a material in fiber form is many times higher than that of the same material in
another form; the thinner the fiber, the greater the strength (A. A. Griffith).
3. The Paradox of the Free Clamped Length
The shorter the length between the clamps, the higher the measured strength of a sample (fiber).
