This paper reports results from an experimental and computational study on the influence of bend radius and internal angle on the damage and impulse transfer characteristics of flexible steel V-structures subjected to localized explosion loading. This issue has bearing on the manufacturing of V-hulls used for Mine Resistant Ambush Protected vehicles used around the world. Global impulse transfer, damage and transient deformation were measured during small-scale explosive detonations on 1:8-scale V-structures. The work found that increasing the bend radius to values that can be used in practical manufacturing generated damage that was less localized than the damage observed in V-structures with tighter bend radii. High-speed imaging was able to measure transient deformation that was maximal in the centre, and lower elastic post-peak vibration magnitudes at high charge masses. The impulse transfer increased as the bend radius increased and the internal V-angle increased. Since V-structures with tighter bend radii exhibit less permanent deformation and higher deformation gradients, they will be more prone to localized ruptures when deployed for blast protection, whereas structures with larger tip radii will need a larger region of the V-structure repaired after a blast event but may be less prone to rupturing when the blast loading is localized.

A novel articulating wingsail design for WASP is developed and an 8.25 m2 prototype has been constructed. This wingsail has potential as a supplementary source of propulsion for cargo shipping. By using wind power, the greenhouse gas emissions from shipping can be significantly reduced. To further develop this wingsail concept, detailed 2D Computational Flow Dynamics simulations have been performed. These suggest that the articulating wing has the potential to provide up to 30% more lift than a fixed aerofoil of the same cross section. These results further suggest that the articulating wingsail concept has potential as a Wind Assisted Ship Propulsion technology.

As the use of more sustainable natural fibres and bio-based resins in fibre reinforced polymers (FRPs) becomes more widespread, their susceptibility to damage due to explosive detonation needs to be evaluated. In this paper, flax and jute FRP panels were blast tested and compared to equivalent mass glass FRP panels. Comparisons were made between flax and glass FRPs manufactured using a synthetic Prime 20 epoxy and a Super Sap epoxy resin containing bio-based raw materials. The transient measurements revealed that all the FRPs exhibited high-peak displacements and viscously damped elastic vibrations. The results showed the predominance of fibre strength and stiffness, and the lesser influence of resin system. The presented modified non-dimensional analysis approach could be extended to predict peak displacement of FRPs during blast events in the future. The failure mode progression for each panel type was identified, providing unique and detailed insights for designers and blast protection engineers. The work should prove valuable to blast protection engineers considering the effects of explosive detonations on structures containing FRPs.

There is currently a poor understanding of blast behaviour of natural fibre composites, yet these materials are extensively used in various other applications. An experimental study was carried out to examine the behaviour of flax fibre reinforced epoxy composites and a South African locally produced medium density fibreboard subjected to uniform blast loading. The transient response was similar for both materials and showed that the evolution of the mid-point displacement was viscous elastic and damped. A similar cracking pattern was observed on the surfaces; however, a different cracking phenomenon were found along the cross-section.

The ability to measure the structural and material response to air-blast loading is vital to developing a proper understanding of near-field blast loading and response. Computational modelling has advanced significantly but, until recently, experimental techniques lagged behind. This paper discusses recent advances in these experimental techniques. The first part describes a bilateral test programme between the UK and South Africa. The high-speed imaging and digital image correlation system at Cape Town gives repeatable and accurate impulse distributions across a central strip of a panel, useful for model validation. Flexural wave behaviour was observed from the transient velocity and displacement profiles, giving good insights into the mechanics of plate response from blast loads. The second part demonstrates the value of high-speed stereo-imaging for measuring the transient response of blast loaded fibre reinforced polymer panels and sandwich structures. The peak displacements. elastic rebounds and transient oscillations provide valuable insights into the damage propagation within these types of structures. The final part of the paper describes some of the continued developments since the success of those early trials, resulting in a new optical diagnostics for blast capability at the University of Sheffield. The imaging system operates at higher frame rates and can cover a wider region of interest on the structure. Ultra-high speed imaging is also shown to be a useful tool for visualising detonations fronts in explosive charges and the expanding fireball.

This paper presents insights into the response and failure of medium density fibreboard (MDF) panels subjected to air-blast loading. The MDF panels are representative of a cheap, and potentially sustainable, structural material that is commonly used in homes and buildings. Simplified computational simulations were used to design a series of air-blast experiments to elucidate a range of responses and failures within the MDF. The blast-loaded MDF panels exhibited multiple surface cracks, substantial in-plane cracking throughout the less dense parts of the cross-section, and fragmentation failures. The transient results show MDF exhibits peak displacement that are many times greater than the permanent deformation, and that the internal damage due to cracking reduced the stiffness of the panels. These findings provide unique and detailed insights into the cracking and fragmentation of MDF that will prove valuable to blast protection engineers considering the effects of explosive detonations inside buildings containing MDF furnishings, and any increased risk of secondary blast injuries due to flying MDF debris. The experimental data can be used by modellers to validate simulations of damage due to explosive events in the future.

Mine resistant ambush protected vehicles often use mono‐V structures in the design of their hulls for blast protection purposes. These hulls deflect blast waves laterally in the event of a landmine detonation directly beneath the vehicle. Lower internal angles offer greater deflection capability, reducing the impulse transfer to the vehicles, but at the cost of increased ride height. This paper reports results of attempts to improve on V‐hull structural designs for air‐blast loading applications, where scaled blast tests are performed to evaluate the designs in terms of structural deformation, rupture and impulse transfer characteristics. Structures with double V and W profiles are compared to mono V structures with a 120° internal angle, such that the proposed designs do not increase the ride height. Results showed that the double V‐structures limit the central deformation, but some designs have severe deformation at the interface of the central V plate and the shallow base angle structure. W structures seem to be susceptible to rupture at low charge masses. There is no single answer to improved blast protection of vehicle hulls, as design choices must be driven by the anticipated threat range, the important performance metrics and other operational considerations.

This paper presents insights into the blast response of sandwich panels with lightweight foam cores and asymmetric (different thicknesses) glass fibre epoxy face sheets. Viscously damped elastic vibrations were observed in the laminates (no core), while the transient response of the sandwich panels was more complex, especially after the peak displacement was observed. The post-peak residual oscillations in the sandwich panels were larger and did not decay as significantly with time when compared to the equivalent mass laminate panel test. Delamination was the predominant mode of failure on the thinner facesheet side of the sandwich panel, whereas cracking and matrix failure were more prominent on the thicker side (which was exposed to the blast). The type of constituent materials used and testing conditions, including the clamping method, influenced the resulting failure modes observed. A probable sequence of damage in the sandwich panels was proposed, based on the transient displacement measurements, a post-test failure analysis, and consideration of the stress wave propagation through the multilayered, multimaterial structure. This work demonstrates the need for detailed understanding of the transient behaviour of multilayered structures with significant elastic energy capacity and a wide range of possible damage mechanisms. The work should prove valuable to structural engineers and designers considering the deployment of foam-core sandwich panels or fibre reinforced polymer laminates in applications when air-blast loading may pose a credible threat.

This paper reports the results of an experimental investigation into the influence of curvature, construction type and load direction on the air-blast response of singly curved sandwich panels with glass fibre reinforced epoxy (GFRE) facesheets and PVC foam cores. Flat and singly curved panels were manufactured using a vacuum infusion technique to investigate the effects of curvature and load direction on the overall blast performance. The panels were mounted in a clamp frame and subjected to air blast loading by detonating discs of plastic explosive PE4 near the panel surface. The influence of load direction was ascertained by performing tests that loaded the curved panels on either the convex or concave surface. Blast test results showed that the convex panels exhibited lower impulse transfer than the concave and flat panels. Convex sandwich panels exhibited lower damage levels for a given charge mass and a higher charge mass rupture initiation on the rear skin than their concave counterparts. Recommendations include increasing the thickness of the front skin to delay the onset of rupture for the sandwich configuration.

An experimental and numerical study was performed on V-plates made from 2 mm thick DOMEX-700 steel. The blast tested plates were manufactured with either a 32 mm or a 62 mm V-tip radius and with a V-angle of 105. or 120.. The plates were subjected to localised blast loads from cylindrical PE4 charges with a 38 mm diameter and a stand-off distance of 34 mm or 50 mm. The numerical simulations were performed in LS-DYNA (R) using a Multi-Material Arbitrary Lagrangian-Eulerian blast model. The experiments were modelled in quarter symmetry with the clamp frames and bolts included in the model. The first series of experiments used a non-deformable material model for both the clamp frames and theV-plate. This was done to obtain information about impulse transfer. In the second series of simulations, the clamp frames were modelled with an elastic material model for steel, while a Johnson-Cook material model used for the steel plates. A larger number of V-tip radii were considered for the numerical simulations, which allowed for trends to be determined across the entire range of V-tip radii. The study found that increasing the V-tip radius resulted in an increase in the measured impulse. The simulations correlated closely with the experiments for impulse. Furthermore, the simulations showed that for very large V-tip radii, there is no significant change in the impulse transferred.

This paper examines the effects of glass fibre configuration and epoxy resin type on the response of glass fibre epoxy-based fibre metal laminate panels. These lightweight materials are excellent candidates for use in transportation applications, where mass is a major factor in design and materials selection. Interfacial bond strength was characterised through single leg bend testing and revealed varying failure characteristics for different epoxy configurations and surface treatments. A combination of bead blasting and silane treatment provided the best surface treatment for the aluminium, while SE84 epoxy resin gave superior adhesion properties compared to Prime 20ULV. Blast tests were performed to investigate the effect of bond strength on panel response under localised and more uniformly distributed air-blast loading conditions. Dimensionless analysis and failure mode identification were used to show that both fibre configuration and bond strength played a role in blast response but the bond strength (and particularly resin type) was more prominent.

This chapter reports the results of an experimental investigation into the influence of curvature, construction type, and load direction on the air-blast response of singly curved glass fiber reinforced epoxy laminate and sandwich panels. Equivalent mass glass fiber reinforced epoxy laminates and PVC foam cored sandwich panels were manufactured using a vacuum infusion technique. Three radii of curvature were manufactured: flat (infinite), convex (+500 mm radius) and concave ( 500 mm radius). The blast test results showed that the laminate panels were superior to the sandwich panels, with higher charge masses required to cause panel rupture. The convex panels exhibited lower impulse transfer than the concave and flat panels. The convex sandwich panels were better than the other sandwich panels, showing lower damage levels for a given charge mass and also higher charge mass rupture initiation for the back face sheet. Recommendations include increasing the thickness of the front face sheet to delay the onset of rupture.

This chapter presents results from a study on the response of singly curved fibre-reinforced polymer (FRP) sandwich panels subjected to close-proximity blast loading. The influence of radius of curvature was explored by manufacturing and testing panels with three external radii of curvature (infinite (flat), 1000 and 500 mm). The loading was generated by detonating 10–30-g circular discs of PE4 plastic explosive at a constant standoff distance of 100 mm. Multiple failure modes were identified by a posttest inspection of the panels. Failure modes of the face sheets included delamination, matrix failure and fibre fracture. Core compression, core shear and fragmentation were observed in the core material. Failure of the FRP sandwich panels was initially more prevalent on the front face sheet and in the core material. Increasing the charge mass resulted in the rupture of the front face sheet and penetration of the core, which caused higher load transfer to the back face sheet. Lower impulses were transferred to the curved panels when compared to flat panels subjected to the same charge mass detonations, although there was no discernible difference between the impulses transferred to the 1000- and 500-mm radius panels. The curved panels were also able to withstand higher charge masses than the flat panels without exhibiting rupture. Failure (particularly delamination) was more prominent along the axis of curvature at low charge masses, but at higher charge masses the failures were more prominent perpendicular to the axis of curvature, particularly rupture and cracking of the face sheets.

The paper reports on an experimental and numerical investigation into the response of sandwich panels, with PVC foam cores and glass fibre reinforced vinyl ester face sheets, to localised blast loading. It also reports on the response of equivalent mass glass fibre reinforced vinyl ester panels. The loading was generated by detonating discs of plastic explosive at a small stand-off distance of 50 mm. Multiple failure modes were exhibited by the panels, including core compression, fragmentation and complete penetration, debonding between the face sheet and core, delamination between the fibre layers and rupture of the fibres. The sandwich panels exhibited complete penetration failure while no penetration occurred in the equivalent mass composite only panels. Reasonable agreement between the experimental results and numerical simulations is observed. The analysis reveals the reasons why the composite only panels perform better than the sandwich panels with PVC foam core. Due to the lower transverse stiffness of the individual components of the sandwich panel, considerably higher transverse velocity of the face sheet develops at the beginning of the process causing larger deflections and therefore larger in-plane stresses in the face sheet despite the high energy absorbing capacity of the foam core. The influence of the core density on the sandwich panel resistance to blast loading is also briefly discussed. (C) 2012 Elsevier Ltd. All rights reserved.

The response of composite sandwich structures to blast loading has received little attention from researchers when compared to the research performed on their metallic counterparts, despite the fact that composite sandwich panels are becoming more generally used in practice. This paper reports on a preliminary experimental investigation into the response of sandwich panels comprising E-glass fibre reinforced vinyl ester facesheets and closed cell PVC foam cores to localised blast loading. The loading is generated by detonating discs of plastic explosive in close proximity to the panel. Multiple failure modes were exhibited by the panels. A failure progression pattern was identified, with increasing impulse: front facesheet delamination, core compression, back facesheet delamination, fibre fracture, core fragmentation, plastic deformation and debonding of the back facesheet following by complete core penetration. No back facesheet rupture was observed, but this was anticipated as the next failure mode to occur at higher impulse levels. The panels with denser cores exhibited lower levels of damage. Theoretical estimates of midpoint displacement were calculated using an analytical beam model. Simple estimates of the delamination, core compression and fibre fracture energies were also made. The energy partition showed that delamination, core compression and fibre fracture were significant energy absorption modes, and that fibre fracture energies exceeded the core compression and delamination energies at higher impulses. This was particularly evident for the lower density core which provided lower resistance to front facesheet deflection. (C) 2011 Elsevier Ltd. All rights reserved.

Electromagnetic interference (EMI) occurs when electronic devices are subject to electromagnetic radiation from unwanted sources at the same frequency ranges that these devices operate. Metals typically serve as excellent EMI shielding agents, but their heavy weight, high cost and susceptibility to forms of environmental degradation make them an undesired choice for many current electronic devices. Conversely fibre reinforced polymeric (FRP) composite materials are normally light weight, and can be cheaper to produce, but typically lack the inherent EMI shielding capabilities that may be required. This research work addresses the viability FRP composite materials for use as EMI shielding structures, specifically for aerospace applications. It was found that carbon fibre could suffice this purpose, but likely required filler materials to enhance electrical conductivity and shielding effectiveness (SE).

Comparatively little research has been undertaken regarding new electromagnetic shielding materials in the past ten years [1]. Fibre reinforced polymer (FRP) composite materials have, however, been identified in recent years as being the desired choice for the replacement of orthodox metallic alloys in many aerospace applications. One of the chief obstacles is the inherent lack of electromagnetic shielding capabilities possessed in most FRP composite materials. Modern aircraft are essentially “fly-by-wire” systems, making them potentially very sensitive to EM interference. Little advancement in shielding has been made since the 1990’s [1] possibly due to the perception that shielding adds mass and offers no value other than EM protection to the electronic device [1].

Attempts to model the degradation of polymer composites have been restricted to modelling the effects of selected degradation mechanisms. No comprehensive model has yet been accepted to predict the effect of the natural environment on the strength of polymer composites. From a review of available literature, it appears that the matrix of a polymer composite is most affected by exposure to the natural environment. Further, the damage appears to progress from the surface into the interior of the laminate. An approach has been developed to determine the properties of the damaged layer and combine the properties of the damaged and undamaged layer to obtain bulk material properties of the laminate.

Due to the lack of durability data for polymer composites in South Africa, a study has been initiated to determine the effect of the South African climate on polymer composites. Laminates exposed and tested were fabricated from two different epoxy resins with woven glass reinforcement. Environmental exposure was conducted at locations with significantly different climates. Compression test results show that while epoxy 1 experienced a negligible change in strength, epoxy 2 appears to have benefited the most from possible post curing during exposure. Cracks on the surface of epoxy 2 have progressed into the laminate but have not as yet reached the first layer of woven fibre after 20 weeks of exposure.

The design, FE analysis, deflection and strength optimisation, manufacture and physical testing of an all-composite camera mounting gimbal for airborne use was discussed. The existing magnesium design is considered too heavy and its metallic structure is both prone to harmonic oscillations and radar detection, thus a new composite design has been proposed. The use of finite element packages allowed the complex fibre angle optimisation to be performed. A number of prototype gimbals were manufactured using a new process of a closed mould technique, with expanding silicone inserts and a pre-impregnated carbon fibre/epoxy resin woven material. Finally, these prototypes were physically tested to check that they met the strength criteria and to confirm the FEA results.