(a) List four reasons why glass fibers are most commonly used for reinforcement. (b) Why is the surface perfection of glass fibers so important? (c) What measures are taken to protect the surface of glass fibers?

The four main reasons why glass fibers are most commonly used for reinforcement are: 1. High strength: Glass fibers have high tensile strength, which makes them suitable for reinforcement purposes. This strength enables them to improve the mechanical properties of composites and help to withstand load in various applications. 2. Lightweight: Glass fibers are lightweight, which makes them suitable for reducing the overall weight of different structures and components. This property can lead to increased energy efficiency and ease of handling and installation. 3. Corrosion resistance: Glass fibers show high resistance to corrosion from chemicals, water, and other external factors. This property makes them suitable for use in harsh environments and applications with exposure to corrosive elements. 4. Cost-effective: Glass fibers are relatively inexpensive compared to other reinforcement materials, such as carbon or aramid fibers. Manufacturers and end-users can benefit from using glass fibers for reinforcement without incurring high costs.

The surface perfection of glass fibers is crucial for the following reasons: 1. Bonding with matrix material: A smooth, clean, and perfect surface allows glass fibers to bond properly with the matrix material, such as polymer resins. This ensures a strong adhesion and effective stress transfer between the fiber and the matrix, which leads to improved mechanical properties. 2. Minimizing stress concentration: Imperfections on the surface of glass fibers, such as cracks or scratches, can act as stress concentrators, leading to a reduction in the overall strength of the reinforced material. A better surface finish can prevent such issues. 3. Enhancing fatigue performance: A perfect surface finish of glass fibers can contribute to better fatigue performance of the composite material. Surface imperfections can serve as initiation points for fatigue failure, so their absence is important for the longevity of the material.

Some common measures to protect the surface of glass fibers include: 1. Sizing application: The fibers are coated with a sizing agent during the manufacturing process. This helps in protecting the fiber surface from abrasion and damage during handling, knitting, weaving, or winding operations. 2. Proper handling and storage: Careful handling of glass fibers during processing and storing them in a controlled environment can protect their surface from damages such as cracks, scratches, or contamination. 3. Surface treatments: Glass fibers can undergo surface treatments, such as silane coupling agents, which can help improve the performance and compatibility of the fibers in various matrix materials. This can also help protect the fiber's surface and improve its overall effectiveness. 4. Protective coatings: In some applications, a protective coating can be applied to the finished composite material to provide additional protection for the glass fibers. This can help maintain the fiber's surface perfection and prolong the material's lifespan.