The performance and application effectiveness of prepregs are primarily determined by their technical parameters, which directly influence the molding process and the ultimate properties of the resulting composite material. Foremost among these is the resin solid content, typically expressed as a weight percentage. Insufficient solid content can lead to inadequate composite strength, whereas excessive content may hinder the layup and molding processes; the common range falls between 30% and 60%.
Fiber volume content reflects the proportion of the total volume occupied by fibers within the composite material. Generally, a higher fiber volume content results in greater material strength and stiffness; however, this may simultaneously lead to a reduction in processability and toughness. For aerospace applications, the fiber volume content of carbon fiber prepregs typically ranges from 50% to 65%, while materials intended for automotive and marine use may feature slightly lower levels.
Viscosity and flow characteristics are also critical parameters. During the layup and hot-press molding processes, prepregs must maintain a certain degree of flowability to ensure uniform resin impregnation of the fibers. Typically, the material is required to exhibit a certain level of thixotropy at room temperature, yet flow and cure rapidly during the heated curing phase. Curing temperature and curing time constitute another set of vital indicators, as they directly impact the final composite material's mechanical properties and thermal stability. For prepregs utilizing various resin systems, the curing temperature range typically spans from 120°C to 180°C, while the curing time varies from a few tens of minutes to several hours, depending on the material thickness and specific processing parameters.
