Scaled simulation of the blast effects on structures using lego blocks: a pilot study

Blast effects on structures is an important topic in this modern age for many practising engineers, including structural engineers designing buildings for safety or weapons engineers attempting to destroy enemy infrastructure. Due to the large costs, time demands, space requirements and expertise required, full scale testing is rarely a feasible approach. As such it is important to be able to effectively model the blast effects on structures. Currently, computer modelling techniques are extensively used, however the results of these models are often difficult to verify, whilst requiring experienced expert users to ensure accurate data

Testing the blast response of foam inserts for helmets

Modern era combat helmets have different iterations and configurations to offer greater protection from blunt impact or ballistic penetration to suit the theatre of operation, although there are currently no standards for blast protection. Moreover, incorporation of blast protection into the same constrained mass-volume envelope is extremely challenging as there is very little space for a material to absorb or dissipate the shockwave. Foam padding is fitted in contemporary combat helmet designs for comfort and standoff purposes. Examples were subjected to blastwaves generated from an air-driven shocktube, along with open cell polyurethane foam specimens of varying pores per inch and thicknesses to. Whilst the range of samples tested did not afford any superior blast mitigation behaviour over the foam already present in helmets, they exhibited comparable performance with a lower mass. There also appears to be positive correlation between increased mass and increased impulse transmitted through the foam. The literature suggests that multiple mechanisms of damage for blast induced mild Traumatic Brain Injury (bTBI) can be caused by the helmet itself, therefore additional protection from a blunt or ballistic impact may increase the risk of damage from a blast insult

Woven fabrics in book conservation: An investigation into the properties of aerolinen and aerocotton

Woven fabrics commonly referred to as ‘aerocotton’ and ‘aerolinen’ are frequently used in the conservation of books and manuscripts and are valued for their strength and flexibility. Although textiles have a long history in the production and repair of books, aerocottons and aerolinens are relatively recent materials adopted from early aircraft production. In 2007, the main supplier of these woven fabrics to the UK conservation community ceased production, and new producers started supplying a range of woven fabrics under the labels of ‘aerocotton’ and ‘aerolinen’. Understanding the strength, composition, and longevity of repair materials is central to conservation practice and this investigation tested two linens and two cottons alongside the discontinued cotton to quantify the relative strengths of the fabrics. Each fabric was tested before and after laundering, and in three directions (warp, weft, and bias). The tests conducted measured mass per unit area, thickness, sett, tensile strength, folding endurance, and dimensional change. In tensile strength tests the bias-cut fabrics were weakest but extended the most, whilst those cut in the weft direction were strongest. The cottons lasted longest in terms of folding endurance and the samples cut on the bias were the fastest to break. The dimensional change tests showed that washing affected the linens more than the cottons and that across all fabrics there was a greater amount of shrinkage in the warp direction. It is hoped that these results will provide concrete information to guide conservators in the preparation and use of aerocottons and aerolinens

Ballistic protective properties of material representative of English civil war buff-coats and clothing

One type of clothing system used in the English Civil War, more common amongst cavalrymen than infantrymen, was the linen shirt, wool waistcoat and buff-coat. Ballistic testing was conducted to estimate the velocity at which 50% of 12-bore lead spherical projectiles (V50) would be expected to perforate this clothing system when mounted on gelatine (a tissue simulant used in wound ballistic studies). An estimated six-shot V50 for the clothing system was calculated as 102 m/s. The distance at which the projectile would have decelerated from the muzzle of the weapon to this velocity in free flight was triple the recognised effective range of weapons of the era suggesting that the clothing system would provide limited protection for the wearer. The estimated V50 was also compared with recorded bounce-and-roll data; this suggested that the clothing system could provide some protection to the wearer from ricochets. Finally, potential wounding behind the clothing system was investigated; the results compared favourably with seventeenth century medical writings

Blast mitigation using polymeric 3D printed auxetic lattice structures - a preliminary study

Protection of critical infrastructure in an urban environment is a challenging task, specifically against the vehicle bourne improvised explosive device threat. To design infrastructure to withstand this evolving threat, novel solutions and advanced materials need to be developed. One such material of interest are auxetics. This study experimentally analysed the mitigation of blast response of auxetic re-entrant honeycomb structures, with geometries varying between −ve 30° and +ve 30° using additive manufacturing (3D printing) techniques and non-explosive loading via shock tube. Re-entrant auxetic structures (−ve 15°) exhibited repeatable blast mitigation of 23% and reduced the transmitted pressure and impulse of the blast wave. Further highlighting their potential application as a protective measure to enhance a structures blast survivability