Limin Jin

Comparisons of static bending and fatigue damage between 3D angle-interlock and 3D orthogonal woven composites

This paper presents the comparisons of quasi-static three-point bending and fatigue damage behaviors between the three-dimensional angle-interlock woven composite and the three-dimensional orthogonal woven composite. The stress–deflection curves and failure modes were recorded to compare both composites’ mechanical properties under quasi-static bending loading condition. The S-N curves were obtained to demonstrate the comparison of fatigue life under various stress levels between three-dimensional angle-interlock woven composite and three-dimensional orthogonal woven composite. In addition, the damage indexes versus number of cycles (D-N) curves were given to characterize the three-stage cumulative fatigue damage evolution of both types of textile structural composites. Furthermore, the ultimate damage morphologies were compared to deduce the structural effects of the composites under three-point bending cyclic loading condition.

Three-point bending fatigue behavior of 3D angle-interlock woven composite:

This study reports the three-point bending fatigue behavior of three-dimensional angle-interlock glass/polyester woven composite (3DAWC). The S–N curve was obtained under the different bending stress levels. The bending stress vs. bending deflection curves were recorded to show the stiffness degradation and bending deformation of the 3DAWC during the fatigue test. The failure modes of the 3DAWC under the different fatigue loading conditions were photographed and compared with those in quasi-static bending tests. It was found that the integrated construction structure of the 3D angle-interlock woven fabric can resist the delamination of the 3DAWC under high-cycle fatigue loading. The cracks propagation and breakages of the warp yarns that run through the thickness direction of the 3DAWC dominate the fatigue failure. The resin cracks and resin-yarn interface debonding are the secondary factors for determining the fatigue behavior.

Experimental characterizations of bending fatigue of a four-step 3-D braided rectangular composite under different stress levels

This article reports the bending fatigue behavior of a four-step 3-D rectangular braided composite at different stress levels. The S–N curve and the stress vs. deflection history were recorded to investigate the bending fatigue behaviors of the braided composite. Specifically, the area of the stress hysteresis loop in each loading cycle and the accumulated area of the whole loading cycles were calculated from the stress vs. deflection history curves. All the integral areas were compared at different stress levels for analyzing the energy absorption. Then, the energy absorptions during the bending fatigue were compared to analyze the energy dissipation mechanisms taking place during the fatigue process. The stiffness degradation was also calculated to show the fatigue damage. The damage morphologies of the 3-D braided composite specimens were photographed to compare the failure modes under different stress levels.

Experimental and numerical analyses of the mechanical behaviors of three-dimensional orthogonal woven composites under compressive loadings with different strain rates

Quasi-static and high strain rate compressive behaviors of basalt/vinyl ester 3D orthogonal woven composites along three perpendicular yarn directions were investigated experimentally and numerically. An elastic–plastic numerical model based on the 3D fabric architecture of the 3D orthogonal woven composites was developed to analyze the compressive deformation and failure mode under different strain rate loading conditions. The stress–strain curves obtained from experimental along three directions were used to validate the finite element model. The agreement between the experimental and finite element model results proves the validity of the finite element model. From the experimental results, the strain rate sensitive and anisotropy of the compressive behaviors was found. The finite element results were employed to analyze the locations of stress propagation, the 3D stress state, and the progressive failure behavior. It was also found that this model has a similar failure shape of “broom” at one end of the composite along both of weft and warp compressive directions, while an inclined shear band was formed in through-thickness compression. This result indicates that Z-yarn contributed significantly to the in-plane responses. Additionally, the absorbed energies that induce the complete damage of the composite coupons at various strain rates were also calculated and discussed.

Finite element simulation of three‐dimensional angle‐interlock woven fabric undergoing ballistic impact

This paper presents finite element simulations of three‐dimensional (3D) angle‐interlock woven fabric (3DAWF) undergoing ballistic impact. A micro‐structure model of the 3DAWF was established at the fiber tow level. Incorporated with commercial finite element code, ABAQUS/Explicit, the ballistic impact damage of the 3DAWF was simulated and compared with that in the experiment. Residual velocities of the conically cylindrical steel projectile (Type 56 in Chinese Military Standard) with different strike velocities were calculated and verified with those in the experiment. There are good agreements of the impact damage of the 3DAWF and the residual velocities of the projectile between finite element results and experimental results. The acceleration fluctuation record of the projectile and the stress wave propagation in the 3DAWF obtained from the simulation reveal the impact damage mechanisms of the 3DAWF. The strain rate effect of the fiber tows on the ballistic performance are also discussed. Such a micro‐structure model could be extended to the design of the impact behavior of the 3DAWF composites.

Experimental investigation and numerical simulation of three-point bending fatigue of 3D orthogonal woven composite

This paper reports the three-point bending fatigue behavior of three-dimensional (3D) orthogonal woven composite (3DOWC) in experimental and finite element analysis (FEA) approach. In experimental, the S–N curve was obtained to illustrate the relationship between applied stress levels and number of cycles to failure. The stiffness variation was recorded to present the degradation of mechanical properties of the 3DOWC during the process of fatigue loading. Furthermore, the fatigue damage morphologies of the tested 3DOWC coupons were given to indicate the damage modes of different parts (resin, yarns, and their interface) of the composite under the range of stress levels. In FEA approach, a user-defined material subroutine UMAT which characterizes the stiffness matrix and fatigue damage evolution of the 3DOWC was developed and incorporated with a finite element code ABAQUS/Standard to calculate the maximum deflection of the 3DOWC during each loading cycle. The bending deformation at different loading cycles was also calculated. From the comparisons between FEA and experimental approaches, it is indicated that the proposed model is reasonable for calculating the fatigue bending deformation.

Cumulative Fatigue Damage for 3-D Angle-Interlock Woven Composite Under Three-point Bending Cyclic Loading

This article presents the quantitative characterization of cumulative fatigue damage behavior for the three-dimensional angle-interlock woven composite undergoing three-point bending cyclic loading. The S–N curve was obtained to demonstrate the fatigue life of the three-dimensional angle-interlock woven composite under different stress levels. The increment of cycles for each 5% interval of stress level was reported to show the difference of fatigue resistance performances of the three-dimensional angle-interlock woven composite among the high, middle, and low intervals of stress level. In addition, the Cumulative Fatigue Damage versus Number of Cycles (D–N) curve and the Deflection Index versus Number of Cycles (F–N) curve were deduced to characterize the three-stage cumulative fatigue damage. Furthermore, the damage morphologies of the three-dimensional angle-interlock woven composite after fatigue tests were photographed to compare with those in quasi-static test. The cracks initiation and propagation in the three-dimensional angle-interlock woven composite during the process of cyclic loading were summarized to find the mechanisms of fatigue damage development.

Finite element analyses of stress distributions of three-dimensional angle-interlock woven composite subjected to three-point bending cyclic loading

This paper presents the finite element simulation of stress distribution features of 3D layer-to-layer angle-interlock woven composite undergoing three-point bending cyclic loading. With the finite element analysis model, a microstructure shell element model of the woven composite at yarn level was established to calculate the fatigue behaviors and stress distribution during cyclic loading. The stress distributions in the warp, weft yarns, and the resin regions have been calculated to show the stress difference in the woven composite. It has been observed that the warp yarns share the most part of the stress or loading, i.e. the strength warp yarn is more important than that of the weft yarn for the fatigue design. In addition, the stress distributions at the locations where the weft yarns crossover the warp yarns have been investigated. The stress degradations of the top and bottom surface of the woven composite panels were also compared with those in experimental and good agreement was found. With the stress distribution in the woven composite, the method of improving the fatigue damage tolerance was expected to be developed.