Flexural and compressive residual strength of composite bars subjected to harsh environments

Abstract

This work aims to evaluate the degradation mechanisms of selected composite bars subjected to exposure to various chemical environments. Sets of three different groups of bars, such as glass fiber reinforced epoxy pultruded at Wroclaw University of Science and Technology (WUST), commercial glass fiber reinforced epoxy overwrapped with carbon fiber, and hybrid bars (H-bar) manufactured by a combination of pultrusion and filament winding methods. The hybrid bar is a composition of a pultruded carbon fiber reinforced epoxy core and the filament-wound glass overwrap. The research included a macro and microscopic evaluation of bars before and after 50 days of degradation in three types of chemical solutions, that is, 5% NaCl, 5% H2SO4, NaOH with pH = 12 and a comparative analysis of bar damage mechanisms under the influence of compressive and tensile forces. These loading conditions are provided by an out-of-plane compression test, which allows one to assess the quality of the matrix, especially in unidirectional bars, where the applied force is carried only by the matrix. Furthermore, the four-point bending test is performed to assess the flexural behavior of the investigated bars. Research has shown that the most degrading solution is 5% H2SO4 causing the greatest drop in the maximum force concerning the exemplified specimens. Moreover, the most resistant to aggressive environments and mechanical degradation appears to be the “H” hybrid bar; its greater resistance may be affected by the additional filament-wound glass layer, which protects the carbon fiber core.