| Carbon fiber resin-based composites have good mechanical properties,combined with lightweight,safety,comfort and reliability,and are the most desirable materials for light weighting in aerospace.The paper prepares LT-5028 and 692-9G epoxy resins as substations through the resin transfer molding(RTM)process,and composite materials with 24K-T300 flat carbon fiber braids as enhancer.The optimal RTM process parameters were selected and the performance of the high temperature environment was studied through the detection of resin-based characteristics,process optimization,performance and thermos oxygenation test.The curing heat peak area of the two epoxy resins is large,and the heat release is obvious,indicating that the curing agent is suitable.LT-5028 resin after cooling after secondary heating found DSC spectral non-curing heating peak,692-9G resin after cooling secondary heating found DSC spectral non-curing heating peak,proving that the system has been fully cured.24K-T300 carbon fiber in the heating process DSC curve shows a steady upward trend,no obvious peaks,indicating that the surface of carbon fiber without surface modifier changes.Pre-experiments show that the optimal RTM process injection pressure is 2.5MPa and the injection speed is 40ml/min.Mechanical tests show that the 24K-T300/LT-5028 carbon fiber resin-based composite has an extrusive strength of 439.04 MPa,a bending strength of459.17 MPa,and a bending strength of 493.13 MPa,and a bending strength of 530.68 MPa.The shape of the break indicates that the RTM optimization process achieves the full wetting of the resin and fiber interface between the wire bundles of the reinforced body and between the fiber cloths.There are three main ways to stretch the fracture process: the break of carbon fiber,the brittle fracture of epoxy resin and the destruction of the interface between carbon fiber and epoxy resin,all of which hinder the break of carbon fiber composite materials.After the aging of thermos oxygen,the surface deformation and the cut-off graph found that the aging of thermos oxygen can cause damage to the bond ability of carbon fiber and resin surfaces and interfaces.The results show that the loss of moisture in the composites is the main reason for the weight loss of carbon fiber composites.The physical aging is the main reason in the early stage of aging,and the chemical aging is the later stage of aging.The high temperature environment has little effect on the mechanical properties of 24K-T300/692-9G carbon fiber resin matrix composites,while it has a greater impact on the mechanical properties of24K-T300/LT-5028 carbon fiber resin matrix composites.With the extension of thermal oxygen aging time,the mechanical properties of the composites show a downward trend.The results of DMA showed that with the increase of temperature,the storage modulus and loss modulus of the two kinds of carbon fiber composites first increased and then decreased with the aging time;with the increase of aging time,the loss factor TanĪ“ peak and loss modulus peak moved to the high temperature direction,and the glass transition temperature increased.The results show that resin 692-9G is more suitable for high temperature service than LT-5028. |
