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George’s Wood Julian Vincent
of glass fibres, gluing tubes with the same winding angle into beams for testing. He then broke the beams in bending, producing a fracture surface very much like wood (Fig. 4). The experiment showed that when the glass fibres were wound at an angle of 15˚ to the long axis of the tube, the material was very tough indeed, requiring a lot of energy to break it (Fig. 5).
In a separate series of experiments, George, Jim, and a colleague, Richard Chaplin, developed another method based on corrugating sheets of preferred orientation pre-preg, which are sheets of soft, uncured, fibreglass with the fibres oriented parallel to each other (https:// www.fibreglast.com/product/aboutprepregs/Learning_Center). The sheets were assembled with the angle of fibres between adjacent sheets at about 12˚ to each other (Fig. 6). Although this resists fracture in a slightly different manner from the model wood made from tubes, it is still light and tough. The two wood analogues were then tested in impact (a falling weight) compared with specially toughened aluminium and steel, oak and plywood. Under these conditions, George’s Wood was 5 times tougher, weight-for-weight, than the toughest steel (Table 1). Here are some of the uses suggested and experimented with, mostly using the wood analogue of Fig 6: • A bullet fired at a 1 cm thick plate is stopped; the bullet penetrates part way and is held within the material. We have light-weight bullet proof armour replacing the current ceramic plates (heavy) or Kevlar vest (stops the bullet, but deflects and allows bruising of the body). Possibly
Figure 4. Fractured sample of George’s Wood showing sections of the tubes (right) and the way in which they break (left) producing curling segments of the tube walls which resemble the splinters from wood.
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