Hybrid composites of silica glass fibre/nano-hydroxyapatite/polylactic acid for medical application

Fibre reinforced composites (FRC) have shown great potential for the application of internal bone fixation due to mechanical properties that are similar to those of human cortical bones. Ternary composites of silica glass fibres, nano-hydroxyapatite (n-HA) and polylactic acid (PLA) were prepared by compression moulding and their mechanical properties were characterized in this study. With the volumetric content of glass fibre remained constantly at 30% and the volume fraction of n-HA increased from 0% to 5%, the flexural strengths of composites decreased from 625.68 MPa to 206.55 MPa, whereas a gradual increment of flexural modulus from 11.01 to 14.08 GPa were observed at the same time. Within a 28-day degradation period, the flexural strengths decreased by 30%, while no obvious trend of modulus variation was found. The flexural properties of all composites prepared in this study were all found to be close to the reported flexural properties. On the other hand, as more n-HA were incorporated, the water absorption percentages increased, whereas negligible mass loss were recorded. SEM images revealed that the impregnation of fibre mats was poor as loose fibres were observed, which shall be solved in future research to further improve the mechanical properties as well as endurance against degradation. © 2017 International Committee on Composite Materials. All rights reserved

Investigation of fire protection performance and mechanical properties of thin-ply bio-epoxy composites

Hybrid composites composed of bio-based thin-ply carbon fibre prepreg and flameretardant mats (E20MI) have been produced to investigate the effects of laminate design on their fire protection performance and mechanical properties. These flame-retardant mats rely primarily on expandable graphite, mineral wool and glass fibre to generate a thermal barrier that releases incombustible gasses and protects the underlying material. A flame retardant (FR) mat is incorporated into the carbon fibre bio-based polymeric laminate and the relationship between the fire protection properties and mechanical properties is investigated. Hybrid composite laminates containing FR mats either at the exterior surfaces or embedded 2-plies deep have been tested by the limited oxygen index (LOI), vertical burning test and cone calorimetry. The addition of the surface or embedded E20MI flame retardant mats resulted in an improvement from a base line of 33.1% to 47.5% and 45.8%, respectively. All laminates passed the vertical burning test standard of FAR 25.853. Cone calorimeter data revealed an increase in the time to ignition (TTI) for the hybrid composites containing the FR mat, while the peak of heat release rate (PHRR) and total heat release (TTR) were greatly reduced. Furthermore, the maximum average rate of heat emission (MARHE) values indicated that both composites with flame retardant mats had achieved the requirements of EN 45545-2. However, the tensile strengths of laminates with surface or embedded flame-retardant mats were reduced from 1215.94 MPa to 885.92 MPa and 975.48 MPa, respectively. Similarly, the bending strength was reduced from 836.41 MPa to 767.03 MPa and 811.36 MPa, respectively

A stochastic overlap network model of electrical properties for conductive weft yarn composites and their experimental study

Conductive weft yarn composites were developed and studied by both computational and experimental methods. A simulation based on a stochastic overlap network model (SONM) was developed in MATLAB to predict the through-thickness electrical conductivity (TTEC) for conductive weft yarn composites. Conductive weft yarn composites based on Inter-Woven Wire Fabric (IWWF) were manufactured and investigated. The results confirm that the technique can be used to increase the TTEC in a controlled manner by forming a continuous electrically conductive network with a comparatively low volume fraction of conductors. The TTEC of typical cross-ply conductive weft yarn composites reached 446 S/m, which is three orders of magnitude times higher than the control laminate. The simulated data are consistent with the experimental results, offering good scope for predictive design work

Effect of silane coupling agent on the properties of recycled carbon fibers reinforced bio-based epoxy composites

In this work, the effect of a silane coupling agent on the mechanical behavior of recycled carbon fiber reinforced bio-based epoxy composites was studied. For this purpose, the surface of the recycled carbon fiber was treated with 3-aminopropyltriethoxysilane (APS) agent at the concentrations in the 0-8 wt.% range. Dynamic mechanical analysis and characterization of the tensile and flexural properties were performed to observe the mechanical behavior of the specimens, and the morphology of the fracture surface after mechanical testing was also studied by scanning electron microscopy. It was found that the glass transition temperature and the tensile and flexural strengths of the composites increased with an addition of a suitable amount of the silane agent (< 4 wt.%), which was attributed to the cross-linking and curing reaction between the amino groups of APS and the epoxy matrix that improved the interfacial bonding. Thus, an appropriate concentration of the silane coupling agent can improve the mechanical properties of recycled carbon fiber reinforced bio-based epoxy composites

Development of highly electrically conductive composites for aeronautical applications utilizing bi-functional composite interleaves

With the wide application of composite materials in modern aerospace industry, multifunctional carbon fibre composites are likely to play an important role in next generation aircraft. Here, carbon fibre reinforced epoxy composites were produced by using Functionalized Interleaf Technology (FIT). The electroless copper-nickel plated polyester veils (CNPV) were used as the interleaves to replace the initial resin-rich interlaminar regions with functional interlayers. The latter shows useful toughening efficiency, in which the G(Ic) and G(IIc) values for interleaved specimens increased by 59% and 31%, respectively. At the same time, the in-plane (sigma(xy)) and through-thickness (sigma(z)) electrical conductivities were also improved from 74.12 S/cm to 1079.6 S/cm and 1.5 x 10(-3) Skill to 5.29 S/cm, respectively. Moreover, it is found that the effective electric contact area at electrodes was increased by incorporating additional functionalized veils. Therefore, the interleaf material can be characterized by its bi-functionality as it provides both toughening efficiency in the interlaminar region and the ability to form an electrically conductive path crossing the resin-rich interlaminar layer, perpendicular to the laminate plane. (C) 2020 Elsevier Masson SAS. All rights reserved