Effect of Material Composition on Impact Energy Absorbing Capability of Composite Laminates

A novel experimental method was proposed for characterizing the energy absorbing capability of composite materials during the progressive crushing process under impact loading. A split Hopkinson pressure bars system was employed to carry out the progressive crushing tests under impact loading. The stress wave control technique was used to avoid the inhomogeneity of dynamic stress field in the specimen. The progressive crushing behavior was successfully achieved by using a coupon specimen and anti-buckling fixtures. With increasing strain rate, the absorbed energy during the crushing process slightly decreased, whereas the volume of the damaged part clearly increased regardless of material type. Consequently, the energy absorbing capability decreased with increasing loading rate. The effects of material composition, such as fiber type, matrix type and fabric pattern, on energy absorbing capability were also investigated by using the proposed method.

Numerical Simulation of the Dynamic Stress Field Based on DEFORM in the Friction Stir Welding of Al Alloy

Friction stir welding (FSW) was a new solid-state metal-joining method and force played an important role in the weld forming. The study of dynamic stress field helped to understand the forming mechanism of FSW and residual stress after welding. Regarding FSW of aluminum alloy, this paper built the finite element model which was based on DEFORM-3D software and achieved numerical simulation of the dynamic stress field in the FSW process. The results indicate that the peak of stress field appeares in the front side of weld and distributed asymmetrically along the center of the weld; the axial force playes an important role to the distribution of stress field, the the distribution of stress field becomes more intensive as the downforce largen; the stress gradient of the advancing side of weld changes larger than that of the retreating side; the stress near the shoulder experiences twice peak.

Study on the Response of Composite Material Cylinder with Metal Liner under Thermal Mechanical Impact

As to the composite cylinder with metal liner under the high temperature and high pressure, thermal mechanical coupling mechanism and response are studied. On the basis of equations for coupling thermal and mechanical impact load and the non-linear thermoelastic finite element equations, the 3-D analysis model of the composite cylinder is established by using the finite element method. The direct coupling analysis is conducted and the variation regularity of the dynamic stress field is obtained. The results show that the thermal mechanical impact loads can cause large transient stress, which influences the strength of the metal liner obviously.