DVD成型玻璃纤维/环氧树脂复合材料湿热老化特性及层间剪切性能OA

With the increasing sizes and structural complexities of aerospace composite components,the conventional autoclave(AC)manufacturing process faces significant limitations due to high costs,elevated energy consumption,and restrictions on component dimensions.These practical constraints have motivated research into alternative processing routes that can deliver comparable material quality at lower cost and with fewer size restrictions.This work focuses on the double vacuum debulking(DVD)process as a promising Out-of-Autoclave(OoA)technique for manufacturing glass fiber/epoxy composite laminates.Specifically,the study aims to optimize the curing parameters for DVD processing and to systematically evaluate the resulting composite laminates in terms of porosity,hygrothermal moisture absorption behavior,and interlaminar shear strength(ILSS),thereby providing a theoretical and experimental basis for engineering applications.Thermal analysis using differential scanning calorimetry(DSC)was first conducted on BP/EW100 A-200 glass fiber/epoxy prepreg to establish a suitable DVD curing cycle.Based on DSC results,the optimized DVD curing parameters were determined as a two-stage schedule:105℃for 30 minutes for initial curing followed by 127℃for 50 minutes for complete curing.Composite laminates with different ply configurations,including[0]16,[0]24,and[0]32,were subsequently fabricated using the optimized DVD parameters and,for comparison,via traditional AC and single vacuum bag(SVB)processes.Porosity measurements revealed that the DVD-processed laminates are equivalent to that of AC laminates,which is significantly lower than that of SVB laminates.The moisture absorption behavior of the laminates produced by all three processes was evaluated under standardized hygrothermal conditions.Moisture uptake curves were analyzed and interpreted using a Fickian diffusion model,with results indicating a three-stage diffusion process.In the initial stage,moisture ingress was dominated by pre-existing pore networks,accounting for approximately 30％of the total moisture uptake.During the intermediate stage,polymer matrix swelling became the controlling mechanism,while in the late stage,changes associated with polymer aging dictated further moisture diffusion,reflecting matrix plasticization and interface degradation under prolonged hygrothermal exposure.ILSS testing was performed on dry and hygrothermally aged specimens for all laminate types.Both DVD and AC laminates exhibited higher ILSS values than SVB laminates across all ply configurations and test conditions.Statistical fitting of the ILSS data demonstrated that,under both room-temperature and hygrothermal conditions,ILSS decreased by 8.86％and 10.99％,respectively,for each 1％increase in laminate porosity.When compared directly with AC-processed laminates,the dry ILSS values of DVD laminates ranged from 99.83％to 104.17％of AC values,while the ILSS after hygrothermal aging reached 85.04％-106.34％of AC values.These comparisons indicate that the DVD process can achieve mechanical performance on par with or even exceeding that of the AC process and markedly superior to SVB processing.Microscopic observations of the interlaminar fracture surfaces following ILSS tests further illuminated failure mechanisms associated with different manufacturing processes.Scanning electron microscopy revealed that DVD and AC laminates possessed uniform resin coverage on fiber surfaces and tight fiber/matrix interfacial bonding,indicative of effective load transfer and cohesive failure behavior.In contrast,SVB laminates exhibited regions of poor resin adhesion and exposed fibers,suggesting weaker interfacial bonding and a higher propensity for premature interface debonding under shear loading.In summary,the optimized DVD process effectively reduces porosity while maintaining high interlaminar shear performance,making it a viable OoA alternative to the high-cost AC process for thick composite structures.The findings reported herein provide a reliable processing reference not only for the manufacture of large and complex composite parts but also for life prediction and structural repair applications.The demonstrated improvements in hygrothermal resistance and mechanical performance support broader adoption of DVD processing in aerospace composite manufacturing and offer a scientific foundation for future investigations into environmental durability and performance-based design of glass fiber/epoxy composite laminates.