Characterization of Hygrothermal Diffusion Parameters in Fibre Reinforced Polymeric Composites

Abstract

The combination of very high specific strength and stiffness, controllable thermal expansion, corrosion resistance and outstanding electrical properties has resulted in the use of fibre-reinforced plastic (FRP) in many applications. Currently, almost every aero-scope company is developing products made with fibre-reinforced composite materials. In the near future, aircraft will be built with a very high percentage of components made from composite materials [1, 2]. The final stage is the ‘all-composite airplane’ that many people have dreamed of building for several year.

One of the key questions in using composite materials as air-craft components is the degradation of the material due to moisture absorption through long years of service. The mechanical properties of composites which are controlled by the matrix or the matrix/fibre interface, for example shear, flexural, compression, and axial (± 45) tensil strength and stiffness, maybe affected by the absorbed moisture, especially when measured at high temperature. In service, moisture absorbed from the environment causes an average increase of weight by about 1 – 4% in composite components [3].

Deformation is also possible upon change of temperature and upon absorption of moisture. The matrix material is much more susceptible to hygrothermal deformation than the fibre. The temperature change and moisture absorption result in the development of hydrothermal strains that may change mechanical properties [4].