Influence of voids on interlaminar shear strength of carbon/epoxy fabric laminates

The effects of voids(void content,void shape and size)on the interlaminar shear strength of[(±45)_(4)/(0,90)/(±45)_(2)]_(S) and [(±45)/0_(4)/(0,90)/0_(2)]_(S) composite laminates were investigated.Specimens with void contents in the range of 0.2%-8.0%for [(±45)_(4)/(0,90)/(±45)_(2)]_(S) and 0.2%-6.1%for[(±45)/0_(4)/(0,90)/0_(2)]_(S) were fabricated from carbon/epoxy fabric through varying autoclave pressures.The characteristics of the voids were studied by using optical image analysis to explain the interlaminar shear strength results.The influences of voids on the interlaminar shear strength of the two stacking sequences were compared in terms of the void content and size and shape of the void.The effect of voids on the initiation and propagation of interlaminar failure of both stacking sequence composites was found.

Tribological behaviour of fused deposition modelling printed short carbon fibre reinforced nylon composites with surface textures under dry and water lubricated conditions

Fused deposition modelling(FDM)printed short carbon fibre reinforced nylon(SCFRN)composites were fabricated.The friction and wear behaviour of printed materials were systematically investigated under both dry sliding and water lubricated conditions.The results showed that with short fibre enhancements,the printed SCFRN achieved a lower friction coefficient and higher wear resistance than nylon under all tested conditions.Further,under water lubricated conditions,the printed SCFRN exhibited a low,stable friction coefficient due to the cooling and lubricating effects of water.However,the specific wear rate of the printed specimens could be higher than that obtained under dry sliding conditions,especially when the load was relatively low.The square textured surface was designed and created in the printing process to improve materials’tribological performance.It was found that with the textured surface,the wear resistance of the printed SCFRN was improved under dry sliding conditions,which could be explained by the debris collection or cleaning effect of surface texture.However,such a cleaning effect was less noticeable under lubricated conditions,as the liquid could clean the surface effectively.On the other hand,surface textures could increase the surface area exposed to water,causing surface softening due to the higher water absorption rate.As a result,the samples having surface textures showed higher wear rates under lubricated conditions.The work has provided new insights into designing wear resistant polymer materials using three-dimensional(3D)printing technologies,subjected to different sliding conditions.

Deflection analysis of reinforced concrete beams strengthened with carbon fibre reinforced polymer under long-term load action

This paper presents the results of an experimental research on reinforced concrete beams strengthened with an external carbon fibre reinforced polymer(CFRP) layer under long-term load action that lasted for 330 d.We describe the characteristics of deflection development of the beams strengthened with different additional anchorages of the external carbon fibre composite layer during the period of interest.The conducted experiments showed that the additional anchorage influences the slip of the external layer with respect to the strengthened element.Thus,concrete and carbon fibre composite interface stiffness decreases with a long-term load action.Therefore,the proposed method of analysis based on the built-up-bars theory can be used to estimate concrete and carbon fibre composite interface stiffness in the case of long-term load.