Effects of manufacturing technology on static, multi-frequency dynamic mechanical analysis and fracture energy of cross-ply and quasi-isotropic carbon/epoxy laminates

The magnitude of improvement of mechanical properties of laminates using expensive technologies is important to justify the investment in new equipment. The objective of this research is to evaluate the mechanical properties of a cross-ply and quasi-isotropic symmetrical plain weave carbon-epoxy laminate produced with a vacuum bagging method and an autoclave processing method for a given set of epoxy/carbon fabric types. Autoclave-processed laminates exhibit higher static strengths, higher moduli in tension, compression and bending but lower Charpy impact toughness. New findings about materials properties were deduced from dynamic multi-frequency tests between 1 Hz and 50 Hz where it was found that the activation energy was 1.8 times higher in autoclave-processed specimens. Autoclave laminates had, on an average, 1.7-times lower damping ratio in the glassy plateau region and a 3-times lower peak damping ratio in the glass transition region than wet lay-up specimens.