Strength and Failure Modes of Hoop Wound CFRP Tubes Under Compressive High Rates of Loading
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Strength and Failure Modes of Hoop Wound CFRP Tubes Under Compressive High Rates of Loading R. AHMAD1, , F. A. R. AL-SALEHI1 , S. T. S. AL-HASSANI1, and M. J. HINTON2
1 School of Mechanical, Aerospace and Civil Engineering, University of Manchester, PO Box 88, Sackville Street, Manchester M60 1QD, UK 2 QINETIQ, Fort Halstead, Seven oaks, Kent TN14 7BP, UK
(Received 9 December 2004; accepted 20 January 2005) Abstract. A study was undertaken to investigate the response of hoop wound carbon fibre reinforced plastic (CFRP) tubes to dynamic compressive loading at strain rates in the range of 5–200/sec. An experimental rig was designed and built to test short tubular specimens under external radial pressure with minimum end constraints. The load was applied by detonating a small explosive charge inside a water filled, steel, cylindrical chamber enclosing the test specimen. For each test the external pressure and the strains, in both circumferential and longitudinal directions, were recorded on suitable digital processing equipment. Two distinct modes of failure were identified; material and structural (buckling). The mode of failure was dependent on the rate of loading and the tube diameter/thickness ratio. For 100 mm diameter tubes with diameter/thickness = 40, buckling failure dominated at strain rates below 10/s. However, at higher strain rates, material failure and a considerable enhancement in burst strength was observed. For 100 mm diameter tubes, with diameter/thickness = 80, a buckling mode of failure was in evidence in all the tests, irrespective of the rate of loading. Key words: CFRP tubes, modes of failure, compressive strength, buckling of tubes, strain rate effects.
1. Introduction Fibre reinforced composites are now widely used in components within the aerospace, automotive, defence and sporting goods industries, due to their high strengthto-weight ratio and high resistance to corrosion and impact. Many of these components are subjected to dynamic compressive loading, with the possibility that the material, and hence component structural response, may deviate significantly from predictions based on conventional, quasi-static materials test data. From a design perspective, therefore, an in-depth understanding of the effect of strain rate on the compressive mechanical properties of this class of materials would be advantageous. Presently at School of Mechanical Engineering, University Sains Malaysia, Pulau Pinang, Malaysia. Corresponding author.
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Research into the compressive behaviour of polymer composites is often clouded by the difficulties associated with interpretation of the data, which in general exhibit considerable scatter. A variety of failure modes has been recorded under compressive loading of CFRP specimens including [1–4], buckling, end crushing, longitudinal splitting, interfacial failure and shear failure modes. The literature indicates that compressive failure in laminates is inherently complex. For instance, buckling can be subdivided into ma
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