The mechanism of traumatic amputation of limbs by explosion is presented. A survey of blast casualties from Northern Ireland revealed that amputations through joints were very uncommon--the principal site was through the shaft of the long bones. Computer modelling of a bone exposed to blast forces reinforced the hypothesis developed from the casualty survey, that the primary mechanism of the bone injury was the direct coupling of the blast wave into the tissues. The fracture occurs from the resulting axial stresses in the bone, prior to limb flailing from the gas flow over the limb. The gas flow completes the amputation. Field trials employing a goat hind limb model have confirmed the hypothesis. Having identified the mechanism, concepts to develop protective clothing may now be proposed.

Depth-sensing nanoindentation of clay/poly(ethylene oxide) nanocomposites has shown significant differences in the mechanical behavior of the composites, depending on method of synthesis and clay content. In general, the clay/polymer nanocomposite approach can dramatically improve the hardness, stiffness, and creep resistance of the polymer. However, these improvements are dependent on the clay content. At lower concentrations, the improvements are not significant, because of an adverse effect on creep behavior.

Explosive blast causes a pattern of injury including primary blast lung, secondary fragment injury and traumatic amputation of limbs. Major traumatic amputation is rare in survivors of bomb blast but common in those who die. The mechanism of such injury has not been previously determined, but must be established if protective measures are to be developed for members of the armed forces. The nature of 41 traumatic amputations in 29 servicemen who survived to reach medical care after blast injury was investigated to determine the anatomical level of amputation and the pattern of soft tissue damage. Joints were an infrequent site of amputation and the tibial tuberosity was a particularly frequent site of lower-limb severance. Comparison of the pattern of injury was made with that seen in ejecting fast-jet pilots, who frequently suffer major flailing injury; there appears to be a substantially different injury distribution. The accepted mechanism of traumatic amputation, avulsion by the dynamic overpressure, is challenged; it is suggested that the shockwave resulting from an explosion is capable of causing at least bone disruption in a limb.

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An understanding of flow behaviour of polymer melts through a slit die is extremely important for optimizing die design and, consequently, for die performance in processing polymer sheets and films. In view of the complex nature and the physical properties of polymer melts as well as of die geometries, such as coat-hanger dies, no simple mathematical formulae can be used to compute the flow regimes within dies. This paper illustrates the development of a three-dimensional (3-D) computer model of an example of a coat-hanger die design using the computational fluid dynamics package, FIDAP, based on the finite element method. A difference of only 3.7% was found when comparing the velocity distribution at the die exit obtained from the 3-D simulation with that calculated using a twodimensional analytical design procedure, indicating that full 3-D analysis seems to be unnecessary. However it has been shown that unwanted flow phenomena and production problems can be ameliorated by means of visualization and the detailed information obtained from computer simulations. Comparative simulation results with polymers of different rheological properties in the same die are also described. The comprehensive analyses provide a means of interpretation for flow behavior, which allows modification of the die geometry for optimal design.