Fa Zhang

Impact compressive behavior and failure modes of four-step three- dimensional braided composites- based meso-structure model

This paper reports a meso-structure model of 3D-braided composites for the analysis of compressive behaviors and failure modes under quasi-static and high-strain rate compression. An idealized geometrical model of 3D-braided composite, which has the same preform meso-structure with four-step 3D-braided composite is established for finite element analyses of compressive behaviors. The compression stress–strain curves obtained from experimental along the in-plane and out-of-plane directions were used to validate the finite element analyses model. The agreement between the experimental and finite element analyses results proves the validity of the finite element analyses model. It was found that the finite element analyses model provides a way to obtain the locations of stress propagation, the 3D stress state and the progressive failure behavior. The numerical results also showed that the fiber tows in the surface and corner area of braided preform play an important role during both quasi-static and high-strain rate loading.

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.

Static and low-velocity impact on mechanical behaviors of foam sandwiched composites with different ply angles face sheets

The current studies give a brief account of analysis of static and low-velocity impact on foam sandwiched composites comprising composite faces from carbon/epoxy and cores from Rohacell (polymethacrylimide). The face sheets consist of four different stacking sequences as unidirectional, cross-ply, angle-ply and quasi-isotropic, which were fabricated by using hand lay-up process. Later, the composite panels were subjected to quasi-static and low-velocity impact loading using MTS and an instrumented Drop-Weight Machine (Instron 9250HV), respectively. The load-displacement curves have been obtained to characterize the failure mechanisms in the face sheets and the core. Impact parameters were evaluated and compared for different types of sandwich structures. Failure modes were studied by sectioning the samples at the impact location and observing under optical microscope. The results evaluated from static test have shown that the unidirectional have the highest peak load. However, the dynamic test data indicated that the foam sandwich with unidirectional face sheet have lowest peak load, lowest displacement at peak load and minimum energy absorption. It has also been observed that largest damage size, highest penetration depth and shear cracking have been experienced by unidirectional as compared to cross-ply, angle-ply and quasi-isotropic face sheets.

Numerical modeling of the mechanical response of basalt plain woven composites under high strain rate compression

The compression behaviors of 2D plain woven basalt/vinyl ester resin composites along the thickness direction under high strain rates have been investigated experimentally and by use of finite element analyses. The compression stress–strain curves, compressive damage, and rate sensitivity of the compressive behaviors was obtained experimentally. The dynamic responses including the compression stress–strain curves, compression damages, and energy absorptions of the plain woven composite samples were predicted based on finite element analyses at the microstructure level. From the finite element analyses results, it was concluded that the plain woven fabric structure and the rate dependent behaviors of the matrix were the key factors which affect the strain rate sensitivity of the compressive properties. The plain woven fabric structure distortion, instability of woven architecture, and matrix crack were the main failure modes of the plain woven composites under high strain rate compression. The compressive behaviors of plain woven composite could be improved with better design of the woven fabric structures and superior matrix properties.

Damage behaviors of woven basalt-unsaturated polyester laminates under low-velocity impact

This paper describes the damage behaviors of plain-woven basalt-unsaturated polyester laminates under low-velocity impact from experimental and finite-element approach. Experimental tests were carried out in an INSTRON® drop-weight machine with different initial impact energy levels varying from 15 J, 30 J, 50 J, and 70 J with specimen thicknesses of 4 mm. The results showed that as the impact energy increased, the peak force, the energy absorbed, i.e. area under the force–displacement curve, and the damage area increased. The damage mechanism included matrix crack, delamination with fiber bending, and breakage. Finite-element analyses were carried out to verify further the impact mechanism and correlation between these parameters with the induced damage by using software ABAQUS®. The finite-element method results were in good accord with the experimental results regarding peak force, maximum absorbed energy, and damage area.

Damage Behaviors of Foam Sandwiched Composite Materials Under Quasi-Static Three-point Bending

This paper reports the quasi-static three-point bending damage behaviors of foam sandwiched composites in finite element analyses (FEA) and experimental. Finite element calculations were performed to characterize the static response of foam sandwich composites with different ply angle face sheets. Quasi-static three-point bending tests were conducted with a MTS materials testing system to obtain the load–displacement curves and energy absorption under quasi-static bending. A crushable foam model was used in order to explore the mechanical behaviors of core materials, while the Hashin criterion was employed to predict the failure of the face sheets. The load–displacement curves show a satisfactory agreement between the experimental and numerical results. The finite element calculations can also be used to obtain the failure mode included the core damage, face sheet damage and face-core interface damage. It can be observed that the damage at the core material can be classified as either core cracking or core crushing. The damage of the face sheet was through matrix cracking and delamination, with fiber breakage. The significant indentation occurs as a result of the fiber breakage. The face-core interface crack was typically induced by the cracks initiated from the tensile side and propagated to the compressive side.

Finite element modeling of compressive properties of three-dimensional woven composites under various strain rates

The compression properties of three-dimensional angle-interlock woven E-glass fabric/vinyl ester composite material along thickness direction under quasi-static (0.001 s−1) and high strain rates (800, 1600, and 2700 s−1) were investigated with finite element method and compared with those in experimental. The finite element method model was based on the three-dimensional woven composite microstructure. It was found that the compressive properties are sensitive to strain rate both in finite element method and experimental. The finite element method results showed good agreements with that of experimental in stress–strain curves and fracture morphologies. The obvious strain rate sensitivity of the compression properties and failure modes of three-dimensional angle interlock composites was both verified with the finite element method model and results in experimental. The compressive stiffness and maximum compressive stress increased with the strain rate while the failure strain showed an opposite trend. The failure mode is mainly in shear failure. The compressive failure mechanisms have been analyzed from the different components of the three-dimensional woven composites.

Investigation and Exploration of a New Indoor Air Filtration Material

In this paper, a new type indoor air filtration material was developed using three raw materials (wool, carbon fiber and activated carbon powder). Optimum fabrication parameters were adopted in needle-punched process to fabricate the air filtration material. The effect of carbon fiber, wool layer number and activated carbon powder content were analyzed in thermal stability test and formaldehyde removal test, and results showed the addition of carbon fiber enhance the thermal stability, and synergistic effect of wool and activated carbon powder played an essential role in formaldehyde sorption process.

LabVIEW-Based Data Acquisition System for Loom Performance Assessment

In order to improve the efficiency of the test system for loom performance assessment, a new data acquisition system of loom performance based on LabVIEW was developed according to direct memory access (DMA) transfer method. Through given hardware components and tested on a Toyata air-jet loom, the different signals were collected and transferred to computer. Then these signals were processed and the test parameters could be reckoned and shown on the PC screen by special designed software program. The result showed that this virtual test system can satisfy the requirement of loom measurement.

A Comparative Experimental Investigation of 3D Angle-Interlock Woven Composite between Quasi-Static Tension and Three-Point Bending Loading Conditions

As one new kind of 3D textile structural composite which has a strong potential in the application field of structural engineering, the mechanical behavior of 3D angle-interlock woven composite (3DAWC) needs to be extensively investigated. In this paper, a comparative experimental analysis of 3DAWC between quasi-static tension and three-point bending loading conditions were described, which has not been well studied so far. To evaluate the mechanical properties of the 3DAWC, the stress-strain/deflection curves were obtained under quasi-static tension and three-point bending loading, respectively. Furthermore, the Young’s modulus and peak values in stress were also compared. All of these results show that the 3DAWC has good integral performance.