Study On Mode Ⅰ Interlayer Fracture Toughness Of Particles Modified Epoxy Resin Matrix Composites In Different Environments

Carbon fiber reinforced epoxy resin composites have high specific strength and specific modulus among structural materials,and are widely used in the aerospace field,marine field and medical device field.In practical applications,composite products will inevitably be affected by impact external forces and lead to delamination,which seriously affects the service life and safety performance of composite materials.Therefore,the interlaminar fracture toughness of the products can be improved by adding toughened materials.In this paper,fracture toughness experiments were conducted for epoxy resin-based carbon fiber reinforced composites with and without particle modification under different environments,and FESEM maps,3D fracture morphology and surface roughness were obtained using high resolution field emission Scanning electron microscope and confocal scanning electron microscopy for analysis.The main studies in this paper include:（1）ModeⅠfracture toughness study of different particle modified epoxy resin matrix composites under dry environment.Usingα-Al₂O₃with 0.5wt%,1wt%and3wt%and MWCNTs with 0.1wt%,0.3wt%and 0.5wt%modified epoxy resin were used to prepare seven epoxy resin-based carbon fiber reinforced composites with and without particle modification with a layup of[0°]_8sby vacuum assisted transfer molding（VARTM）process,and the specimens of these seven types of composites were interlaminar fracture toughness experiments under modeⅠin dry environment,and their cross sections were scanned by FESEM and confocal laser scanning microscope to reveal the toughening effect of particle-modified epoxy resin-based carbon fiber composites in dry environment,and the fracture mechanism of carbon fiber composites with and without particle-modified epoxy resin matrix in dry environment was investigated.The results show that the toughening effect of MWCNTs on composite laminates under dry environment is better than that ofα-Al₂O₃,especially the toughening effect of 0.3wt%MWCNTs is outstanding,mainly through CNTs pull out of the resin in the form of long fibers,resin and carbon bridging fiber being stretched and deformed or even fractured,crack deflection and so on.With the increase of particle content,the fracture toughness values of the composites show a trend of first increase and then decrease.and the average values of G_IC-prop（Extended Fracture Toughness Value）at the crack extension in particle-modified composites to 85～125 mm increased by26.9%～171.7%,and the average values of surface roughness increased by14.98%～161.96%.（2）ModeⅠfracture toughness study of different particle-modified epoxy resin matrix composites under moisture environment.The interlaminar fracture toughness experiments under modeⅠin moisture environment were conducted on seven types of composite specimens,and their fracture surfaces were scanned by FESEM and confocal laser scanning microscope to reveal the toughening effect of particle-modified epoxy resin matrix carbon fiber composites under moisture environment,and the fracture mechanism of carbon fiber composites with and without particle-modified epoxy resin matrix under moisture environment was investigated.The results showed that the overall toughening effect of MWCNTs on composite laminates under moisture environment is higher than that ofα-Al₂O₃,but the toughening effect of 1wt%α-Al₂O₃is the best,mainly because the water penetration resistance and crack ductility resistance ofα-type alumina reduce the damage of moisture absorption on composites and the brittleness of resin is improved by moisture absorption.The average values of G_IC-propat crack extension in particle-modified composites to 85～125 mm improve by 55.3%～77.7%,and the average values of surface roughness improve by 22.02%～109.76%.（3）ModeⅠfracture toughness study of homogeneous particle-modified epoxy resin matrix composites under different environments.The fracture toughness experimental results of 0.5wt%,1wt%and 3wt%α-Al₂O₃and 0.1wt%,0.3wt%and0.5wt%MWCNTs in dry/moisture environments were compared,and the FESEM,3D fracture morphology and surface roughness of these six experimental groups were compared and analyzed.The contrast reveals the toughening effect and fracture mechanism of particle modified epoxy carbon fiber composites in different environments.The results showed that The toughening effect of 0.5wt%,1wt%and 3wt%α-Al₂O₃modified composites in moisture environment is better than that in dry environment,the average values of G_IC-propat the crack extension in particle-modified composites to 85～125 mm improve by 34.62%,75.45%,61.10%,and the average values of surface roughness improve by 25.46%,28.24%,57.92%respectively The toughening effect of MWCNTs modified by 0.1wt%,0.3wt%and 0.5wt%in moisture condition is obviously lower than that in dry condition.The average values of G_IC-propis reduced by 7.09%,33.92%and 27.75%respectively,the average values of surface roughness decrease by 2.54%,27.85%and 18.29%,respectively.