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Introduction
Published in Sumit Sharma, Composite Materials, 2021
The existence of composite is not new. The word “composite” has become very popular in recent four-five decades due to the use of modern composite materials in various applications. The composites have existed from 10000 BC. The evolution of materials and their relative importance over the years are depicted in Figure 1.1. The common composite was straw bricks, used as a construction material. Then, the next composite material can be seen from Egypt around 4000 BC where fibrous composite materials were used for preparing the writing material. These were the laminated writing materials fabricated from the papyrus plant. Further, Egyptians made containers from coarse fibers that were drawn from heat-softened glass. One more important application of composites can be seen around 1200 BC from Mongols. Mongols invented the so-called modern composite bow. The history shows that the earliest proof of existence of composite bows dates back to 3000 BC – as predicted by Angara Dating. The bow used various materials like wood, horn, sinew (tendon), leather, bamboo, and antler. The horn and antler were used to make the main body of the bow as it is very flexible and resilient.
Materials selection for sports equipment
Published in Steve Haake, The Engineering of Sport, 2020
Archery bows have been used for many tens of thousands of years; the earliest arrowheads found in North Africa, already rather sophisticated, date back to about 50,000 BC. Originally designed for hunting and warfare, the archery bow today has developed into a high-tech piece of sports equipment. Bows may be divided into two classes, simple or ‘self’ bows made singly of wood or wood like materials such as bamboo or palm, and composite bows with layers of various kinds of material, traditionally such as wood, sinew, bone or horn, nowadays such as wood, carbon-fibre and glass-fibre reinforced polymers.
Warfare
Published in Jill L. Baker, Technology of the Ancient Near East, 2018
Some of the oldest known bows come from Denmark and date to ca. 6500 bce (Sachers 2009). Together, the bow and arrow were probably one of the earliest human-made weapons, utilized worldwide. The bow consisted of two flexible limbs, usually made from wood joined by a riser, with the limbs connected by a string. Placing an arrow against the string and pulling backward on the string creates compressive force on the belly (middle) of the limbs and places the back section under tension. When this stored energy is released, the arrow is propelled forward. The bow could be made from wood such as ash, oak, and yew.
A multi-objective optimisation study of trimaran hull applying RBF-Morph technique and integrated optimisation platform at two design speeds
Published in Ships and Offshore Structures, 2022
In this section, all integrated parts of an optimisation framework are introduced. The overall structure of an optimisation framework includes geometry parameterisation, numerical simulation set-up and optimisation algorithm (Yang et al. 2014). In the current study, a mesh-based technique is used for modifying the ship hull at mesh level. The objective of the present study is ultimate shape optimisation of the main hull of an inverted-bow multihull ship by minimising its total drag. The obtained hull form in shape optimisation at two high and low speeds are different because ship performance at calm water is not the same. Therefore, ship hull form optimisation at cruise (low Froude number) and sprint speeds (high Froude number) yields a multi-objective optimisation problem. The RANSE-based CFD solver performs all numerical simulations at two multi-design speeds. Software connection is made via HEEDS software. To find the optimum design and related optimised parameters, SHERPA algorithm is used based on the adjusted parameter of optimiser, as shown in Table 2. This platform allows the saving of previous run history for the new initialisation. Accordingly, the velocity and pressure field of the last simulation are interpolated for the new simulation. This capability yields a faster convergence in every simulation run.
A comprehensive approach to scenario-based risk management for Arctic waters
Published in Ship Technology Research, 2022
Martin Bergström, Thomas Browne, Sören Ehlers, Inari Helle, Hauke Herrnring, Faisal Khan, Jan Kubiczek, Pentti Kujala, Mihkel Kõrgesaar, Bernt Johan Leira, Tuuli Parviainen, Arttu Polojärvi, Mikko Suominen, Rocky Taylor, Jukka Tuhkuri, Jarno Vanhatalo, Brian Veitch
Representative load-displacement curves, an example of which is presented in Figure 13(a), are determined for the bow, midbody, and stern regions of the different considered designs and hull areas. The presented load-displacement curve shows how the response of the analysed grillage compares against nominal values. The design load F is compared against plastic capacity Fp as determined using an offset method by Daley et al. (2017) whereby an elastic stiffness is offset by the resultant permanent deformation δ0. The intersection of the offset line with the numerical model value is used to find Fp. Subsequently, the design load is compared against fracture load Ff. Figure 13(b) shows the contours of the plastic deformation at the steps marked with numbers in Figure 13(a).
Effects of nearshore wave reflections on the behaviour of an axe bow trimaran hull
Published in Ship Technology Research, 2021
Christopher Lewis McGibbon, Md Jahir Rizvi
In general, a marine vessel with an axe bow is considered very effective in normal to moderate wavy seas and this is because the bow of the vessel (due to its sliced shape and low buoyancy) cuts through water rather than riding on top of wave crests. However, in heavy seas, an axe bow vessel shows a tendency of digging into waves and taking green water on its deck causing bow trimming and free surface effects. For this reason, the depth of the forward part of an axe bow hull is higher compared to the rest of the body. Since the buoyancy produced by an axe bow is relatively low in comparison with that of the conventional bows, usable deck area at the fore part of an axe bow hull is relatively limited. As a result, load distributions along the length of an axe bow hull are carried out carefully so that bow section carries fewer load but matches with its buoyancy. If an axe bow part of the hull is over-loaded for some reasons, the hull would experience a trim by the bow. Deng et al (2015) studied the effects of trimming and sinkage on the hydrodynamic resistance of a trimaran hull. They identified that both parameters accelerate the total resistance of the hull and the effects become significant when a trimaran hull runs at high speeds. Jiang et al (2016) investigated the hydrodynamic performances of a planing trimaran and discovered that the lift force produced by the connecting structure between the central hull and one of the outer hulls known as tunnel plays an important role in determining the resistance of the hull. The higher the lift force produced by the tunnel, the lower the resistance of a trimaran hull.