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Fiberglass is used a lot in construction materials and in composite materials and floor reinforcement because it is light weight and strong. A lot of people want to know the answer to this question: The raw material used to make fiberglass is just plain ol’ glass, so how does drawing it out into small, thin fibers increase the strength of the material so much? (What is the principle that makes this happen?)

Currently, the academic community provides several explanations for the Source of the High Strength of Fiberglass, and two of the most widely accepted and mainstream approaches are:

1.The Microcrack Hypothesis

According to this hypothesis, the theoretical strength of glass is extremely high (from approximately 2,000 MPa to 12,000 MPa) because its strength comes from the intermolecular forces that create the material. In practice, however, the strength that is measured in tests is much less than the theoretical maximum. The principal cause of the difference between them is:

Glass or fiberglass contain very tiny microcracks in their interior or body, and these microcracks create areas of concentrated stress on the glass. Overall structural strength is weakened by the existence of these microcracks. Surface Microcracks are the most degrading microcracks that can reduce the strength of the Glass structure.

Fiberglass’s strength is much greater than glass due to 2 main reasons:

A very hot temperature was used to make fiberglass, which created a more homogeneous molten glass. This homogeneous nature of the molten glass prevents the formation of microcracks.

The extremely small cross-sectional area of the fibers drastically reduces the probability of internal microcracks being present.

Furthermore, there is a consistent correlation: the finer the fiber, the higher its strength.

This is because finer fibers possess fewer and smaller surface microcracks, which effectively mitigates stress concentration and, consequently, results in superior mechanical performance.

2.The Molecular Orientation Hypothesis

The theory provides a rationale for the microstructure to explain the process.

In the process of drawing and forming fiberglass, the equipment exerts a continuous force of tension on the molten glass. The external force creates order from randomness; the molecules of the fiber align in an orderly manner in the direction in which the tension is being applied.

The ordered arrangement of molecules in a structure strengthens the molecular bonds. When tensile stress is applied to an object with ordered, bonded molecules, the structure will be highly resistant to tensile stress due to the many bonds between molecules that are generally stronger than are the bonds connecting adjacent non-bonded molecules. Therefore, by creating an ordered arrangement of molecules, one increases the tensile strength of the structure.

Two factors contribute to the uultimate strength of fiberglass:

1) the occurrence of fewer and smaller micro cracks;

2) the ordered alignment of molecules during the drawing process.

These 2 basic mechanisms make fiberglass a necessary material in industries such as heat insulation, building reinforcement, corrosion protection, and composite materials.