Investigation of the sorption and tensile response of pultruded E-glass/vinylester composites subjected to hygrothermal exposure and sustained strain

The aim of the present research is to provide insights into the sorption behavior and degradation mechanisms of a unidirectional pultruded E-glass/vinylester composite subjected to synergistic hygrothermal exposure and sustained bending strain for exposure times of up to 2 years. Composite specimens were found to follow a Langmuir-type diffusion behavior in all environments, with departure from that behavior attributed either to material leaching-out, chemical breakdown, interfacial debonding, or central delamination. The composite tensile strength decreased with increasing immersion time and temperature, with high sustained strain levels having a more detrimental effect at elevated temperatures. The initial strength loss was associated with matrix plasticization, while later reductions were caused by the occurrence of mechanisms of fiber degradation and interfacial debonding. Changes in tensile strength were largely reversible as a result of immersion in deionized water at 22 degrees C, but the level of regain decreased substantially at higher immersion temperatures. Finally, failure by delamination was observed to occur in the most severe environments at strength retention levels dependent upon the amount of imposed bending strain.