Glass reinforced polyester

Important general characteristics of GRP elements compared to other building materials and elements are as follows:

GRP has a low weight as well as a high strength to weight ratio.

GRP has moderately good tensile, compressive and shear strength; however, strength is dependent on temperature and at high temperature even moderate stresses can cause failure with time. As the properties of GRP become worse with time, high factors of safety are necessary for long-term loads.

The polyester resin which is used in the production of GRP hardens and cures. However the resin is brittle and needs the strength that is given to it by the glass fibres; generally structural GRP contains between 25% and 60% of glass fibre reinforcement.

GRP has a high coefficient of expansion.

GRP will creep, that is it will continue to deflect, if there is a permanent load on it. The higher temperatures the faster will be the creep. The maximum operating temperature is about 70°C (160°F).

GRP has a low modulus of elasticity and, because it is used in thin sections, deflection is often a critical factor in design. In order to overcome this flexibility GRP is often used in the form of double skin panels in which deflections are easy to control. The modulus of elasticity decreases with increase in temperature and time under load.

Notes:

coefficient n. коэффициент

double skin panel двухслойная панель

operating temperature рабочая температура

Ответьте на вопросы к тексту.

1. What are the advantages of glass reinforced polyester?

2. What are its disadvantages?

3. Why are the glass fibres necessary in GRP?

4. What is the maximum operating temperature of this material?

5. Why is deflection a critical factor with GRP?

6. How is GRP flexibility overcome?

7. What influences the modulus of elasticity of GRP?