Mechanical Deformation Measurement And Damage Detection Investigations Of Carbon/Aramid Hybrid Woven Composites

Due to the hybrid effect,the carbon/aramid hybrid woven composite not only improves the fracture toughness of carbon fibers,but also increases the stiffness of aramid fibers.As an advanced composite,it has been attracting more and more attention at home and abroad,and its mechanical properties have become increasingly demanding.However,the manufacturing process of hybrid woven composites is relatively complicated,and lots of factors that affect deformation damage and expansion behavior.To improve the reliability and safety of carbon/aramid hybrid woven composites,it is of great significance to study the dynamic evolution and damage behavior of carbon/aramid hybrid woven composites.Firstly,in this paper,the amplitude attenuation of the carbon fiber and aramid fiber directions of the carbon/aramid hybrid woven composites were measured,respectively.The AE dynamic signals and speckle images in the tensile loading process of composite were obtained effectively by using acoustic emission(AE)technology and digital image correlation(DIC)method,and tensile deformation and damage failure behaviors of carbon/aramid hybrid woven composites were analyzed,providing a basis for structural design and non-destructive evaluation of carbon/aramid hybrid woven composites.Secondly,in this paper,AE and infrared thermography(IRT)technology were used to monitor the quasi-static three-point bending experiments of thick carbon/aramid hybrid woven composites with different fiber orientations in real time.Based on the characteristics of the AE signal and the surface temperature field,the damage evolution behavior of the composite was studied.At the same time,the damage morphology of internal mesoscopic structure of the specimens was observed with X-ray micro-computed tomography(Micro-CT)scanning,and to explore its failure mechanism.Thirdly,the progressive three-point bending experiment was carried out for carbon/aramid hybrid woven composites.Combined with AE technology and DIC method to monitor the surface deformation and progressive damage initiation/evolution process of composite specimens in real time,and the progressive damage of internal structural of the composite specimens was identified by Micro-CT technology.The bending deformation,progressive damage evolution and failure behaviors of carbon/aramid hybrid woven composites with different fiber orientations were further studied.Finally,this paper used AE technology to regularly monitor of a large wind turbine blade vibration fatigue experiment in a factory.Based on the analysis of AE signal characteristic parameters,the fatigue damage of wind turbine blade was evaluated.Some important conclusions are summarized as follows(1)When sound waves propagate in the direction of aramid fibers in a carbon/aramid hybrid woven composites,the effect of energy absorption and scattering is more pronounced.(2)Fiber orientation has an important effect on the mechanical properties and damage characteristic of carbon/aramid hybrid woven composites.In the bending test,the specimens whose main material direction(warp direction)is carbon fiber showed higher bending strength and quasi-brittle behavior,and the specimens with warp direction is aramid fiber exhibited good toughness.(3)Micro-CT provides an effective means for characterizing the specimen’s internal structure.In the bending test,for the specimens with warp direction is carbon fiber,the macroscopic failure is mainly the shear failure at the top,which propagates along the thickness direction with the kink bands as the source,causing matrix cracks in the surrounding,which then continue into the bulk,subsequently,matrix cracking and delamination are the prominent failure modes.For the specimens with warp direction is aramid fiber,the origin of the damage is thought to be the tow debonding at the bottom,and the main failure modes are delamination and ply fracture.(4)The combination of AE,DIC/IRT and Micro-CT technology,the deformation,damage evolution and failure behavior of composites can be effectively monitored and observed,provides technical support for further elucidating the damage failure mechanism of composites.