Degradation of polymer-based composites in corrosive media: experimental attempts towards underlying mechanisms

In spite of previous studies on the corrosion behavior of glass-fiber-reinforced plastic composites, it is necessary to establish the relationship between the degradation occurring at the fiber/matrix interface of these composites and their mechanical performance. Here we report a series of experimental-based investigations to assess the issue. For this purpose, glass fiber/polyester samples were immersed in HCl (10% wt.) at three different temperatures, 25 degrees C, 50 degrees C, and 70 degrees C. The effects on the bending, tensile and hardness properties, changes in the appearance, and microstructural analyses were evaluated over periods of 1 to 4 weeks of immersion. The results indicated that the bending strength, ultimate tensile strength, Young's modulus and hardness of the samples decreased when exposed to longer exposure duration and/or higher temperature. The polyester degradation was demonstrated by increased surface roughness, cracks and changes in the solution color. In addition, visual inspection of tensile test fracture surfaces and SEM images of the broken sections revealed the drastic corrosion of the fibers and the interface. Finally, atomic absorption spectroscopy (AAS) was carried out, indicating the occurrence of ion exchange reactions. Our results revealed that the underlying mechanism affecting the corrosion happens in the interfacial zone of these composites.