Vacuum-pressure effects on microstructure and mechanical properties of autoclaved epoxy/carbon composite laminates

The influence of autoclave cure vacuum on the microstructure and mechanical properties was studied for a woven carbon fiber/epoxy resin composite laminate, AS4/8552S. The laminates were cured at vacuum pressures varied from 0 to - 0.08 MPa. Their corresponding thickness, density, resin volume fraction, fiber volume fraction, and void content were established accordingly as a function of vacuum pressure. The combined loading compression and short beam shear mechanical tests were determined at 120 degrees C. The results showed that thickness, density, laminate compressive strength (LCS), and interlaminar shear strength (ILSS) varied exponentially with applied vacuum pressure and reached a steady state at the applied vacuum of - 0.04 MPa. However, applying this vacuum level improved thickness, density, fiber volume fraction, and void content by approximately 42.10, 50.97, 46.69 and 99.84%, respectively, compared to that found without a vacuum bag. Pearson's correlation analysis revealed linear variation in ILSS and LCS modulus with density, fiber volume fraction, void content and between laminate compressive modulus (LCM) and density. One-way ANOVA statistical analysis showed that the most critical parameters affecting ILSS are density and void content. It is also shown that all physical microstructural parameters affect LCS, whereas density and fiber volume fraction are the most significant parameters affecting LCM. [GRAPHICS] .