Evolution of cure, mechanical properties, and residual stress during E-beam curing of a polymer composite

摘要

Degree of cure, mechanical properties, and residual stress were measured as a function of E-beam dose. A proprietary cationic toughened epoxy reinforced with IM7 carbon fibers was used in this study. The composite was cured at 0°C (to prevent simultaneous thermal curing) at different dose per pass levels. DSC (Differential Scanning Calorimeter) was used to determine the cure evolution with dose Both DSC and DMA (Dynamic Mechanical Analyzer) were used to determine the T{sub}g. Tensile testing was performed to evaluate the mechanical properties. Radius of curvature due to warping of thin asymmetric composite strips was measured and was used to evaluate the evolution of residual stresses as a function of dose. The pre-preg was also cured thermally to various cure levels and was characterized for the properties mentioned above. Core evolution for 20 kGy / pass irradiation condition differed substantially, beyond 20 kGy, from that for 5 kGy / pass irradiation condition. Lower dose / pass resulted in rapid curing than higher dose per pass. In-complete curing was observed even at 260 kGy. For a given degree of cure, the longitudinal (E{sub}11) and transverse (E{sub}22) moduli for E-beam cured composite were less than that of the thermally cured composite except at 100 kGy when the former was higher than the latter. Transverse strength and failure strain of the composite cured at 20 kGy / pass were higher than that of composites cured thermally and at other dose / pass conditions. Lower dose per pass resulted in lower cure-induced residual stress than higher dose per pass. The relatively higher strength and strain at 100 kGy are attributed to higher residual stress at this dose when compared to other dose levels.