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The surface of carbon fiber is treated with sizing agent containing hydroxylated carbon nanotubes, fullerenols, and graphene oxide, respectively. The effects of carbon nanomaterials and their structures on the surface properties of carbon fiber, the interfacial properties and the mechanical properties of carbon fiber/epoxy composites are investigated. All three types of carbon nanomaterial can improve the interfacial bonding strength and modulus, thereby enhancing the interlaminar shear strength (ILSS) of composites. Moreover, the ILSS increases with the increase of interfacial bonding strength, due to the roughness and the number of active groups. Compared with the composite without carbon nanomaterials, the interfacial bonding strength of the three nanoparticle‐modified composites increased by 14%, 5% and 4%, the modulus increased by 10%, 26%, and 9%, and the ILSS increased by 14%, 8%, and 7%, respectively. The interfacial bonding strength has a more significant impact on the ILSS than the interfacial modulus. Highlights: CNTs, graphene oxide and fullerenols regulate the surface characteristics of carbon fibers.The influence of carbon nanomaterials on the interfacial properties of composites.The relationship between the fiber surface, the interface and the composites. [ABSTRACT FROM AUTHOR]

Carbon fiber reinforced polyamide composites have outstanding properties, but their applications are significantly affected by the service environment. This work evaluates the effects of temperature (25, 80, 140, and 200°C) and hygrothermal conditions on the mechanical properties of CF/PA6 composite containing delamination damage, and studies its damage behaviors and failure mechanisms. After hygrothermal aging, recrystallization of PA6 improves the heat resistance of CF/PA6 composites, but water absorption reduces the interfacial strength of composites, resulting in the decrease of modulus and compressive strength (24% and 42%, respectively). With the increase in temperature, the compressive strength of CF/PA6 composites gradually decreases (from 132 MPa at 25°C to 24 MPa at 200°C), and the failure mode transitions from fiber fractures, interlayer shear fractures, delamination to kinking. In addition, the compressive failure process of CF/PA6 composites is divided into three stages: buckling, delamination bulging and kinking failure. Highlights: Hygrothermal aging reduces the fiber/resin interface performance.Fiber fracture, interlayer shear and delamination convert to kinking failure.The failure process is divided into buckling, delamination and kinking. [ABSTRACT FROM AUTHOR]

Low‐velocity impact damage is one of the main defects of composite laminates, which seriously affects the bearing capacity and service life of composite laminates. Multiple impact experiments of carbon fiber/epoxy composite laminates were carried out under different impact energies. The finite‐element model was established according to the experimental conditions. The impact damage mechanism of laminated plates was studied by means of simulated damage cloud image, water immersion ultrasonic C‐scan, and computed tomography. The results showed that the matrix damage occurred mainly during the whole impact process, and the tensile damage of the matrix was dominant. As the number of impacts increased, the impact resistance of composite laminates decreased and the damaged area increased, with the second impact having the greatest influence on the degree of damage to the laminates; multiple impacts with low energy were easy to cause delamination at the top of the laminated plate. With the increase in impact energy, the damage at the bottom of the laminated plate was more serious, and the propagation mode of delamination damage in laminates changed from top‐bottom to bottom‐up. Highlights: Establishing a multiple impact finite‐element model for composites.Accurately predicting the impact mechanical response of composites.Revealing multiple impact damage evolution of composites by simulation. [ABSTRACT FROM AUTHOR]

The investigations were carried out into the cure kinetics and thermal stability of multifunctional epoxy/anhydride/imidazole/release agent system (matrix) and carbon fiber reinforced matrix composite. Two experimental techniques were applied: dynamic differential scanning calorimetry (DSC) at different heating rates, and non-isothermal thermogravimetric analysis (TGA). The results were indicated that the two-parameter model was found to describe the cure kinetics for the matrix and the composite. The kinetic parameters such as pre-exponential factor, apparent activation energy, and reaction orders were calculated. And, the carbon fiber had a significant effect on the apparent activation energy and the thermal stability. POLYM. COMPOS., 35:596-601, 2014. © 2013 Society of Plastics Engineers [ABSTRACT FROM AUTHOR]

Highlights The effect of membrane thickness of electrospinning polyethersulfone (PES) nanofiber membranes on interlayer toughness and impact resistance of carbon fiber reinforced epoxy resin (CF/EP) composites are researched. Intercalation composites with different nanofiber membrane thicknesses, ranging from 10 to 50 μm, are tested at mode I and mode II interlaminar fracture toughness. The impact resistance of nanofiber membranes with different thicknesses is evaluated by the compression after impact (CAI) strength test. Moreover, nanofiber toughening contributions are investigated using the crack path and surface analysis. Results indicate that PES nanofibers increase the toughness of interlayer resin and change the interlaminar crack propagation path of CF/EP composites. The optimum nanofiber membrane thickness for mode I (GI = + 58%) and CAI (CAI strength = + 33%) is 50 μm, while for mode II is 30 μm (GII = + 16.4%). The storage modulus of CF/EP composites increases with the increase of nanofiber membrane thickness. The study also confirms the insertion of a nanofiber membrane slightly improves the tensile strength and interlaminar shear strength (ILSS) of the CF/EP composites. PES nanofiber membranes of different thicknesses were inserted into the CF/EP. CAI and GI improved by 33% and 58%, respectively of CF/EP composites. The relationship between interlayer fracture toughness and CAI was discussed. [ABSTRACT FROM AUTHOR]