Coupled Effects in Dielectric and Thermal Properties of Polymer Matrix Composite Structures Due to Moisture Absorption

Abstract

Fiber reinforced polymer (FRP) composites are being used in number of fields including aerospace, marine, sports, medical, power sectors, etc. due to their lightweight nature while retaining high mechanical performance in terms of high specific strength, stiffness, and great fatigue properties. However, the applicability of these materials is restricted by their stability up to a certain temperature (i.e. glass transition temperature) and environmental degradation (i.e. moisture, UV light, etc.). Moisture ingression greatly reduces their mechanical properties altering material structure by causing polymer plasticization, chain scission and fiber-polymer interface deterioration. These changes instantaneously affect the thermal properties of the materials which in turn reduces its applicability in real life applications. Broadband dielectric spectroscopy (BbDS) is a robust non-destructive characterization technique that can directly assess the impact of moisture on material properties. In this current work, BbDS has been used to correlate the changes in thermal properties (glass transition temperature, enthalpy change) of glass fiber reinforced polymer composites due to moisture absorption. This work investigated the extent of these effects in conjunction with the dielectric property changes which can be utilized to help understand the material state and reliability in hygrothermal conditions, as well as for structural health monitoring.