Composites In Transverse Direction Research Articles

The alignment of CNTs perpendicular to electric filed resulted in effective electrothermal de/anti-icing performance at high voltage for CNT/XLPE composites

The aligned CNT-based composite in transverse direction to the alignment is considered as completely insulating and unsuitable for utilization in de-icing system. Here, we have found that the aligned CNT-based composite in transverse direction to the alignment exhibited excellent electrothermal performance at high voltage, for the first time. Furthermore, we compared and investigated the electrical and electrothermal performance of the aligned and random non-percolative CNT/crosslinked polyethylene (XLPE) composites at high voltage. A temperature increase of 7.5–72.7 ℃ at a record high voltage of 900–3100 V is reached for the aligned CNT/XLPE composites. The filed emission at high voltage enables the electron to transfer along the CNTs radial direction, resulting in joule heating for the aligned CNT/XLPE composites in transverse direction to the alignment. Besides, the non-percolative structure contributes a temperature increase of 8.2–40.1 ℃ at a applied voltage of 900–2800 V to random CNT/XLPE composites. The high applied voltages is significantly higher than rGO-based composites. More importantly, effective de-icing and anti-icing performance at high voltage of 900–2800 V are achieved for the random non-percolative and aligned CNT-based composites at −20 ℃. These results demonstrate the potential of applying the CNT/XLPE composites in de/anti-icing system of transmission-lines and other fields requiring joule heating at high voltage.

Quasi-brittle fracture criterion of bamboo-based fiber composites in transverse direction based on boundary effect model

Bamboo and engineered bamboo products have gathered increasing scientific and technological interests for its promising applications in sustainable engineering purpose. Bamboo-based fiber composites, a main example of engineered bamboo products, is fabricated from processing the raw bamboo bundles treated with water-soluble resin into a bamboo fiber reinforced bio-composite. The present work investigates the transverse mode-I fracture criterion of bamboo-based fiber composites: the tensile strength ft and fracture toughness KIC. The fiber bundles are taken as the “aggregates” of this material, and the average grain size G is determined as 0.4 mm. By the experimental curve between the applied load and the mid-span deflection from the three-point-bending test on single edge notched specimens, the fracture process as well as the crack development includes three stages: linear, softening and failure stages. The quasi-brittle fracture criterion is calculated with the experimental peak load Pmax according to the boundary effect model in non-linear elastic fracture mechanics. Also, the normal distribution analysis is applied to cover all the experimental scatters with desired reliability. Furthermore, the method in this work on bamboo-based fiber composites can be extended to study other fiber reinforced composites.

Dually self-reinforced Poly(ε-caprolactone) composites based on unidirectionally arranged fibers

Dually self-reinforced Poly(ε-caprolactone) (PCL) composites were prepared to broaden its load-bearing applications as tissue engineering scaffolds. The composites were prepared from bi-component PCL yarns composed of self-nucleated PCL drawn fibers and PCL matrix by a combined process of yarns winding and hot pressing. Differential Scanning Calorimetry (DSC) results showed that incorporating of self-nucleating agents can improve the melting points of the fibers, creating a process temperature window for hot pressing. The orientation parameters of the fibers were accurately measured by Confocal Raman microscopy (CRM) and the results showed that the orientation parameter of the fibers could be up to 0.9 after drawn. Tensile tests showed that the self-nucleated drawn fibers had stronger mechanical properties than the control fibers with the same draw ratios. The hot pressing parameters (temperature and pressure) were also optimized during hot-pressing. The Young's modulus and break strength of the dually self-reinforced composites in longitudinal direction could be up to 118% and 400% higher than that of pristine PCL although their elongation at break decreased. Decline of mechanical properties of the composites in transverse direction was not observed, indicating good adhesion between the fibers and the matrix, which was confirmed by scanning electron microscope analysis.

Mathematical Prediction of Strength of Ablating Polymer Unidirectional Composites in Transverse Direction and in Shear Along and Across Fibers

The scope of the investigations of the paper includes the efficiency in the prediction of strength characteristics of the ablating polymer unidirectional carbon-fiber-reinforced plastics at elevated temperatures based on the properties of the unreinforced matrix and a bundle of fibers in the process of thermal oxidative breakdown at different types of stress state. The characteristics of elasticity and parameters of strength of the transverse-isotropic carbon-fiber-reinforced plastic, as well as of its components (epoxy matrix and carbon fibers of T700 type), have been determined in compliance with the regulatory documents of Ukraine at low heating rates with the subsequent exposure of the specimens at the fixed temperature, when the inertia effects can be neglected. It is illustrated that the variation in densities of the ablating unreinforced matrix and the bundle of fibers at elevated temperatures is rather well described via the models of multiphase media employing the modified integral exponential function. The authors analyze the possibility to evaluate the critical stresses of the transverse-isotropic composite at elevated temperatures based on the mechanics of multiphase media considering the thermal and mechanical characteristics of the ablating polymer matrix and the bundle of carbon fibers. It is assumed that the task of heat and mass transfer can be solved separately from the coupled tasks of thermal mechanics of the ablating materials since mechanical stresses have no effect on its parameters. It is found that the calculation of critical stresses using the hypothesis for the total hermetic sealing between the phases or in the assumption on the low pressure in pores determines the lower and upper lines of variation of the composite strength at different types of stress state. In particular, the calculated strength of the unidirectional composite under tension in the transverse direction and in shear along and across the fibers is in good correlation with the experimental data obtained by the authors and other researches.

Mechanical properties of hybrid structural composites reinforced with nanosilica

Epoxy‐based hybrid structural composites reinforced with 14 nm spherical silica particles were investigated for mechanical properties as a function of nanosilica loading fractions. Composites were fabricated using continuous glass or carbon fiber of unidirectional architecture and nanosilica dispersed epoxy, through resin film infusion process. Uniform dispersion of nanoparticles in resin matrix was ensured by an optimized ultrasound‐assisted process. Although resin viscosity marginally reduces in the presence of nanosilica enabling a better control in composite manufacturing process, glass transition temperature of epoxy remained unaffected at low weight fractions. Compressive strength of hybrid glass or carbon fiber/epoxy composites showed more than 30–35% increase with nanosilica at a concentration as low as 0.2 wt%. Tensile and compressive properties of hybrid composites in transverse direction to the reinforcement remained unaffected. POLYM. COMPOS. 37:1216–1222, 2016. © 2014 Society of Plastics Engineers

Dry Sliding Wear Behaviour of Magnesium Alloy Based Hybrid Composites in Transverse Direction

Wear behaviour of AE42 Mg alloy-based composites reinforced with Saffil short fibres (SSF) and SiC particles (SiCp) in various combinations has been investigated in transverse direction, i.e., the plane containing random fibre-orientation was parallel to the steel counter-face. Wear tests are conducted on a pin-on-disc set-up under dry sliding condition having a constant sliding velocity of 0.837 m/s for a constant sliding distance of 2.5 km in the load range of 10-40 N. It is observed that the hybrid composites reinforced with both SSF and SiCp exhibit better wear resistance than the composite reinforced with SSF alone, because SiCp are harder than SSF and remain intact retaining their load bearing capacity even at the highest load employed in the present investigation. The dominant wear mechanism is observed to be abrasion for all the composites. It is accompanied by fracture and pull-out of SSF from the worn surfaces. Wear behaviour of the composites in transverse direction is also compared with wear behaviour in longitudinal direction, i.e., the plane containing random fibre-orientation was perpendicular to the steel counter-face, reported earlier by the same authors. It is observed that the wear resistance of the composites in transverse direction is lower than that in longitudinal direction due to the lower load bearing capacity, the extensive fracture and pull-out of SSF from the worn surfaces.

Elastoplastic Model of UHMWPE/LDPE Thermoplastic Composites in Transverse Tensile Direction

UHMWPE/LDPE thermoplastic composites present obvious plastic deformation in the off-axis direction, especially in the transverse direction. In this paper, the elastoplastic property of UHMWPE/LDPE composites in transverse tensile direction was studied. Mises yield potential plastic model was used as the plastic model, together with a power hardening law to analyze the plastic behavior of UHMWPE/LDPE composite in transverse direction. Abaqus software and subroutine UMAT were used to simulate the tensile property of UHMWPE/LDPE composites, and the simulation results are accordance with the experiment results very well.

Young's Modulus of Coated Inclusion Composites by the Generalized Mechanics-of-Materials (GMM) Approach

A micromechanical model of the Young's modulus for three special cases of composites - continuous unidirectional fiber composites, particulate composites and periodically bilaminate composites - has been developed within the framework of the mechanic-of-materials approach. Parallel-series (PS) and series-parallel (SP) schemes were adopted based upon opposing combination sequence of the parallel model (direct rule-of-mixture) and the series model (inverse rule-of-mixture). By expressing the inclusion's geometrical characteristics in terms of reinforcement volume fraction and interphase volume, a set of reinforcement parameters for the inclusion and its interphase are extracted. Based on reinforcement parameters for the special cases, those of more general cases, which are intermediates of the special cases, are obtained by curve-fitting approximation. Young's modulus of simple cases such as coated fiber composites in longitudinal direction and coated lamina composites are shown to be approximate to the parallel and series models respectively. Cases such as coated fiber composites in transverse direction and coated particulate composites are compared with other results and observed to be highly and moderately conservative by the PS and SP techniques respectively.