Zhongxiang Pan

Effects of temperature and strain rate on impact compression behaviors of three-dimensional carbon fiber/epoxy braided composites

This paper reports compression properties of three-dimensional carbon fiber/epoxy braided composites at temperatures from 23℃ to 210℃ under strain rate from 1200 s−1 to 2400 s−1. It was found that the elevated temperature has a negative effect on the compression properties, whereas the strain rate effect is positive. The compression modulus has a rapid degradation at the temperature of 120℃ which is close to the glass transition temperature of epoxy resin obtained from the dynamic mechanical analysis. The results also showed that the shear deformation is the main failure mode of three-dimensional braided composites at high strain rates of compression load and high temperatures.

Numerical analyses of thermo-mechanical behaviors of 3-D rectangular braided composite under different temperatures

This paper reports numerical analyses of thermo-mechanical behaviors of three-dimensional (3-D) 4-step rectangular braided basalt fiber/epoxy resin composite materials under different temperatures from 60 to 210°C. In the braided composite, the basalt fiber tows were assumed as thermal insensitive material and the mechanical behaviors of the epoxy resin under different temperatures were tested and introduced in microstructure model of the 3-D braided composite. The thermal stress distributions in fiber tows and resins were numerical calculated based on the microstructure model. The influences of fiber tow orientations and braided architectures on the stress distribution along the axial direction and resins have been discussed to characterize the thermal stress under different temperatures. The residual stress in the braided composite induced from the temperature change is also analyzed for the application of the braided composite to different temperature environments. It is expected that such a numerical investigation could be extended to the design of 3-D braided composite applied to high temperatures.

Thermo-mechanical behaviors of 3-D braided composite material subject to high strain rate compressions under different temperatures

ABSTRACT This article reports the compressive behaviors of 3-D braided basalt fiber tows/epoxy composite materials under the temperature range of 23–210°C with the strain-rate range of 1300–2300 s−1. A split Hopkinson pressure bar apparatus with a heating device was designed to conduct the out-of-plane compression tests. It was found that compression modulus, specific energy absorption, and peak stress decreased with the elevated temperatures, while failure strain gradually increased with the elevated temperatures. Compression modulus and peak stress were more sensitive to the temperature effect, whereas failure strain and specific energy absorption were more easily affected by the strain rate effect. The plasticity can be divided into two types: (a) the platform-shape plasticity; or (b) the slope-shape plasticity. The experimental condition of 150°C with 1827 s–1 was a dividing threshold to differentiate the compression-failure mode and the shear-failure mode. The authentic microstructural finite element analysis results revealed that the distribution and accumulation of the inelastic heat led to the development of shear bands. Braided reinforcement had an important influence on the damage characteristics. When the temperature was below Tg, the material underwent a significant temperature rise during failure. But above Tg, the temperature rise was relatively steady.

Effect of temperature and strain rate on biaxial warp-knitted composite

This investigation aims to study the impact behaviors of biaxial warp-knitted composite materials under the following conditions—strain rates of 1000–3400 s−1; temperatures of 23℃–210℃. Impact compression tests (in the through-thickness direction of specimens) were conducted using the split Hopkinson pressure bar apparatus. A heating device was applied to achieve required temperatures. It was found that high temperatures of 120℃–210℃ led to a softened initial response on the composite’s stress–strain curves. In addition, pre-peak hardening was observed in the specimen when exposed to temperature between 23℃ and 90℃. The latter could be attributed to further compaction with densification effect during through-thickness compression. Finally, two different failure modes were noticed—(1) the shear-oriented failure and (2) the delamination-oriented failure. This was due to the degradation of the tricot, the brittle–ductile transition of the resin, and the thermal stress in the biaxial warp-knitted composite at different temperatures.

Finite element analyses of compressive behaviors of biaxial warp-knitted composite material under various strain rates with a simplified geometrical model

This paper reports the compressive behaviors of biaxial warp-knitted (BWK) composite material under compression with various strain rates. The compression stress–strain curves and the failure modes along three orthogonal directions were obtained from split Hopkinson pressure bar (SHPB) apparatus. A finite element analysis (FEA) model based on a simplified model of BWK composite was also carried out to verify the experimental results. In the simplified model, an equivalence resin (ER) combined tricot yarns with resin, and the stiffness matrix was derived from the mechanical parameters of the tricot yarns and the resin. A good agreement between experimental and FEA demonstrates that the simplified method is applicable of modeling the high strain-rate behaviors. By comparing the experimental damage morphologies with the damage development and morphologies observed from the model, it was found that the FEA model offers a better understanding to the compression damage mechanisms. The model can also be extended to design the impact performance of the BWK composite with high efficiency.