A vertically aligned carbon nanotube/fiber based electrode for economic hydrogen production by water electrolysis

Electrolysis is the most mature form of hydrogen production. Unfortunately, water electrolysis has not yet achieved the efficiency and the cost levels required for any practical application. In order to enhance the current density, modification of the electrolyte and the electrode morphology are the most popular approaches. Recently there have been numerous reports on how to improve the efficiency of hydrogen production by water splitting [1-3]. On the electrode side, the use of non-platinum high efficiency electrode materials for water splitting will provide a promising future for the hydrogen economy. An ideal electrode for water electrolysis should have good permeability to water and gas. It should also offer good electrical properties with a long life. A porous graphite plate, when coated with titania, for example, is known to provide a simple and economical electrode for water electrolysis [4]. © 2010 IEEE.

Impact of carbon fibre/epoxy corrugated cores

The dynamic compressive response of corrugated carbon-fibre reinforced epoxy sandwich cores has been investigated using a Kolsky-bar set-up. Compression at quasi-static rates up to v 0=200ms -1 have been tested on three different slenderness ratios of strut. High speed photography was used to capture the failure mechanisms and relate these to the measured axial compressive stress. Experiments show significant strength enhancement as the loading rate increases. Although material rate sensitivity accounts for some of this, it has been shown that the majority of the strength enhancement is due to inertial stabilisation of the core members. Inertial strength enhancement rises non-linearly with impact velocity. The largest gains are associated with a shift to buckle modes composed of 2-3 half sine waves. The loading rates tested within this study are similar to those that are expected when a sandwich core is compressed due to a blast event. © 2012 Elsevier Ltd.

Multi-hit armour characterisation of metal-composite bi-layers

The ballistic performance of equi-mass plates made from (i) stainless steel (SS); (ii) carbon fibre/epoxy (CF) laminate and (iii) a hybrid plate of both materials has been characterised for a spherical steel projectile. The hybrid plate was orientated with steel on the impact face (SSCF) and on the distal face (CFSS). The penetration velocity (V 50) was highest for the SS plate and lowest for the CF plate. A series of double impact tests were performed, with an initial velocity V I and a subsequent velocity V II at the same impact site. An interaction diagram in (V I,V II) space was constructed to delineate penetration from survival under both impacts. The degree of interaction between the two impact events was greater for the CFSS plate than for the SSCF plate, implying that the distal face has the major effect upon the degree of interaction.

Compressive response of glass fiber composite sandwich structures

Sandwich panels with crushable foam cores have attracted significant interest for impulsive load mitigation. We describe a method for making a lightweight, energy absorbing, glass fiber composite sandwich structure and explore it is through thickness (out-of-plane) compressive response. The sandwich structure utilized corrugated composite cores constructed from delamination resistant 3D woven E-glass fiber textiles folded over triangular cross section prismatic closed cell, PVC foam inserts. The corrugated structure was stitched to 3D woven S2-glass fiber face sheets and infiltrated with a rubber toughened, impact resistant epoxy. The quasi-static compressive stress-strain response of the panels was experimentally investigated as a function of the strut width to length ratio and compared to micromechanical predictions. Slender struts failed by elastic (Euler) buckling which transitioned to plastic microbuckling as the strut aspect ratio increased. Good agreement was observed between experimental results and micromechanical predictions over the wide range of core densities investigated in the study.

Hybrid core carbon fiber composite sandwich panels: Fabrication and mechanical response

Carbon fiber reinforced polymer (CFRP) composite sandwich panels with hybrid foam filled CFRP pyramidal lattice cores have been assembled from a carbon fiber braided net, 3D woven face sheets and various polymeric foams, and infused with an epoxy resin using a vacuum assisted resin transfer process. Sandwich panels with a fixed CFRP truss mass have been fabricated using a variety of closed cell polymer and syntactic foams, resulting in core densities ranging from 44-482kgm-3. The through thickness and in-plane shear modulus and strength of the cores increased with increasing foam density. The use of low compressive strength foams within the core was found to result in a significant reduction in the compressive strength contributed by the CFRP trusses. X-ray tomography led to the discovery that the trusses develop an elliptical cross-section shape during pressure assisted resin transfer. The ellipticity of the truss cross-sections increased, and the lattice contribution to the core strength decreased as the foam density was reduced. Micromechanical modeling was used to investigate the relationships between the mechanical properties and volume fractions of the core materials and truss topology of the hybrid core. The specific strength and moduli of the hybrid cores lay between those of the CFRP lattices and foams used to fabricate them. However, their volumetric and gravimetric energy absorptions significantly exceeded those of the materials from which they were fabricated. They compare favorably with other lightweight energy absorbing materials and structures. © 2013.

The effect of carbon nanotube orientation on erosive wear resistance of CNT-epoxy based composites

Aligned carbon nanotube (CNT) polymer composites are envisioned as the next-generation composite materials for a wide range of applications. In this work, we investigate the erosive wear behavior of epoxy matrix composites reinforced with both randomly dispersed and aligned carbon nanotube (CNT) arrays. The aligned CNT composites are prepared in two different configurations, where the sidewalls and ends of nanotubes are exposed to the composite surface. Results have shown that the composite with vertically aligned CNT-arrays exhibits superior erosive wear resistance compared to any of the other types of composites, and the erosion rate reaches a similar performance level to that of carbon steel at 20° impingement angle. The erosive wear mechanism of this type of composite, at various impingement angles, is studied by Scanning Electron Microscopy (SEM). We report that the erosive wear performance shows strong dependence on the alignment geometries of CNTs within the epoxy matrix under identical nanotube loading fractions. Correlations between the eroded surface roughness and the erosion rates of the CNT composites are studied by surface profilometry. This work demonstrates methods to fabricate CNT based polymer composites with high loading fractions of the filler, alignment control of nanotubes and optimized erosive wear properties. © 2014 Elsevier Ltd. All rights reserved.