A micromechanical study on longitudinal strength of fibrous composites exposed to acidic environment

In this study, a new model is presented to calculate longitudinal strength of unidirectional E-glass/epoxy composites exposed to sulfuric acid environment using the micromechanics theorem. Mechanical properties degradation of resin and fibers, acid penetration depth in the composites over the exposure times and thermal residual stresses are the main parameters affecting the strength of composites. Thus, corrosion tests are separately performed on the glass fibers and epoxy resin and their mechanical properties degradation are measured. The EDX (Energy Dispersive X-ray Microanalysis) analysis is then used to study the elements composition of glass fibers embedded in the composites. The results are utilized to calculate the acid penetration depth in the composites. Furthermore, thermal residual stresses are calculated in two different ways, the micromechanics theorem and a Representative Volume Element (RVE) model using the FEM method. Finally, the magnitude of strength of degraded composites is calculated with and without including thermal residual stresses. Compared to the experimental results, the strength results including thermal residual stresses calculated by the RVE model reveal the most accurate results.