The effect of thermo-oxidative aging on the vibration damping characteristics of the conventional fabric composites reinforced by three-dimensional (3D) and four-directional (4Dir) braided preform and laminated plain woven fabric and the 3D-4Dir braided graphene-based carbon fiber composites was investigated. Specimens were isothermally aged at 140 °C for various periods of time up to 1,200 h. The results indicated that the thermo-oxidative aging resulted in deterioration of the matrix and interface performance, in the form of chain scissions, weight loss, microcracks and interfacial debonding, which should be responsible for the decrease of nature frequency and the increase of damping coefficient of the composites. After aging for 1,200 h, the first nature frequency and first damping coefficient retention rates of 3D-4Dir braided graphene-coated carbon fiber/epoxy composite were 5.5% and 6.4% higher than those of laminated composite, respectively. One of the reasons was the integrated structure of 3D-4Dir braided composite exposed lower fiber end area to air than that of laminated composite, leading to less interface oxidation. Another reason was that the graphene reinforced gradient interphase provided an effective shield against interface oxidation and restricted the movement of the different phase of the materials at the composites interface. This synergetic reinforcing effect of 3D-4Dir braided structure and graphene reinforced hierarchical interface provides an easy and effective way to design and improve the thermo-oxidative stability of carbon fiber reinforced polymer composites. POLYM. COMPOS., 37:2871–2883, 2016. © 2015 Society of Plastics Engineers

This article presents an experimental study of bending properties of multilayer-connected biaxial weft knitted (MBWK) fabrics-reinforced composites made with carbon fibers. Three types of composites are used in bending test, which are three-layer-connected biaxial weft knitted fabric-reinforced composite, four-layer-connected biaxial weft knitted fabric-reinforced composite and five-layer-connected biaxial weft knitted fabric-reinforced composite. Two-way ANOVA analyzing method was used to deal with whether the carbon fiber volume fraction and the cutting direction have significant effect on the bending strength of the MBWK fabrics-reinforced composites. Failure analysis is also available by means of samples debris examination to identify the failure mode. POLYM. COMPOS., 36:2291–2302, 2015. © 2014 Society of Plastics Engineers

This study concentrated on the thermal aging mechanism and lifetime of a carbon fiber laminated epoxy composite. Samples of the laminated composite and the neat resin (as a contrast) were exposed in air circulating ovens set at 90, 120, and 150°C for various periods of time up to 13 days. The flexural properties combining with FTIR, weight loss, DSC, SEM, and surface morphology analyses were performed on the unaged and aged samples. The flexural strength of the composite deteriorated by a factor of 3 as a result of weight loss, microcrack formation, and chain scissions. The two-way ANOVA results indicated that the aging time had significant effect on the flexural strength of the composite and the aging temperature had no significant effect on it. Two statistical models were established to predict the residual flexural strength and lifetime of this composite. POLYM. COMPOS., 35:975–984, 2014. © 2013 Society of Plastics Engineers

The tensile tests of three-dimensional (3Dim) and four-directional (4Dir) carbon fiber braided/epoxy resin composites and carbon fiber woven plain fabric laminated/epoxy composites after heat accelerated aging at 150 and 180°C for 60, 120, and 180 h were carried out respectively. The reason of the changes of tensile property of these composites after different aging period of time at different high temperature was explained. The results of two-way ANOVA analyzing indicate that the aging time has a significant effect on tensile strength of these composites. With the increase of accelerated aging period of time at high temperature, the tensile strengths of these composite samples decreased compared with that of composite samples without aging. However the decrease of tensile strength of 3Dim and 4Dir braided composites is less than that of laminated composites. One of the reasons is after aging for a long time at high temperature, the resin is damaged and becomes brittle which make the bonding force between fiber and resin decrease. Another reason is the structure of reinforcement of composites. After aging, the structure of 3Dim and 4Dir braided/epoxy resin composites still keeps the integrity which makes the 3Dim and 4Dir composites have less tensile performance degradation (3Dim and 4 Dir: three-dimensional and four-directional). POLYM. COMPOS., 2012. © 2012 Society of Plastics Engineers