The specific energy absorbed during the axial collapse of a variety of graphite, Kevlar and glass fiber composite tubes was determined. Although structural collapse occurred by a fracture failure mode, the specific energy absorption was higher than that of high strength metal tubes which col lapsed by buckling, over a wide range of tube geometries (t/D ratios), provided that the correct trigger mechanism was used to initiate the failure. Little change in the specific energy absorption was observed over a wide range of compression rates or with temperature changes below 20°C; above 20°C the effect of temperature varied with the resin employed. Collapse occurred initially by interlamellar shear followed by fiber fracture. The results were correlated on the basis of the specific interlamellar shear stress which permitted the energy absorption values for a variety of materials to be compared.
The crystal structures of [Cu,(bipyam-H),CI,]-H,O (I ) and [Cu,(bipyam-H),Br,]-H,O (2) where bipyam-H = bis(2-pyridyl)amide, have been determined by X-ray analysis, in the orthorhrombic space group Pnn2: ( I ) , a = 14.092(3), b = 12.895(3), (c) = 1 1 .I 90(2) A, Z = 2, and R = 0.032 for 2 453 observed and 2 029 unique reflections; (2), a = 14.1 86(3), b = 13.040(3), c = 11.31 3(2) A,
The collapse characteristics and energy absorption of a variety of tubes made in glass, graphite and Kevlar fiber composites have been examined. Tubes made from glass or graphite fibers collapsed by a fracture mode. There was a critical range of tube geometry over which stable collapse occurred with high energy absorption; thinner wall tubes tended to collapse in an unstable manner with lower energy absorption. Changes in the lay-up which increased the modulus increased the energy absorption of the tube. Tubes made from, or including Kevlar fiber, tended to collapse in an unstable mode by buckling rather than by fracture, which led to low values for specific energy absorption.
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