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Applied Composite Materials: An International Journal for the Science and Application of Composite Materials (v.9, #5)
Effect of Material and Geometry on Crushing Behaviour of Laminated Conical Composite Shells by E. Mahdi; A. M. S. Hamouda; B. B. Sahari; Y. A. Khalid (pp. 265-290).
This paper examines the effects of the material and structural geometry on the crushing behaviour, energy absorption, failure mechanism and failure mode of circular conical composite shell. The static crushing behaviour of circular conical composite shell under uniform axial compressive load has been investigated experimentally. The cone vertex angles used were 0, 6, 12 and 18 degrees. The cone vertical length and bottom outer diameter were kept for all the cases as 100 and 110 mm, respectively. Failure modes were examined using several photographs taken during the crushing stages for each specimen. Results obtained from this investigation showed that the initial failure was dominated by the interfacial and shear failure, while the delamination and eventually fibre fracture were dominated the failure mechanism after the initial failure. It has also found that the static crushing behaviour of the circular conical shell is very sensitive to the change in the vertex angle. Reinforcement type greatly affects the energy absorption of the circular conical and cylindrical shells.
Keywords: circular conical composite shells; specific crushing energy; filament wound laminated; hand lay-up; crushing behaviour; splaying mode
The Transfer of Matrix Toughness to Composite Mode I Interlaminar Fracture Toughness in Glass-Fibre/vinyl Ester Composites by P. Compston; P.-Y. B. Jar; P. J. Burchill; K. Takahashi (pp. 291-314).
The transfer of matrix toughness to composite mode I interlaminar fracture toughness (G Ic ) has been investigated in unidirectional glass-fibre reinforced composites with brittle and rubber-toughened vinyl ester matrices. Single-edge-notch bend (SENB) and double cantilever beam (DCB) specimens were used for matrix and composite G Ic characteristion, respectively. The initial crack opening displacement rate was used as the parameter for comparison of G Ic results. Matrix G Ic was completely transferred to composite G Ic for crack initiation (G Ic -init) in the brittle-matrix composites, but in the toughened composites transfer was only partial due to the presence of fibres. The conclusion is that the maximum contribution to energy absorption by the matrix is more accurately reflected by G Ic -init, and should be used for further assessment of the enhancing effect of fibre bridging during steady-state crack propagation, instead of matrix G Ic . A plot of composite G Ic for steady-state crack propagation, G Ic -prop versus G Ic -init indicates that the enhancing effect of fibre bridging is greater in the toughened composites. This enhancement is related to a larger deformation zone size in the toughened matrices.
Keywords: vinyl ester; matrix toughness; mode I interlaminar fracture toughness; fibre bridging
Damage Constitutive Equations and its Application to Fiber Reinforced Composites under Transverse Impact by Dazhi Jiang; Wei Shen; Xingye Wang (pp. 315-329).
Two continuous field variables, called as continuity tensor and damage variable tensor, are used to describe the anisotropic responses of an elastic-brittle material under transverse impact load. Based on the continuum damage mechanics, anisotropic damage constitutive equations in both full and incremental forms are proposed here. The expressions of effective elastic module tensor, damage variable tensor and damage propagation force tensor are further derived, and the methods for determining the tensors are explained in detail. An example of strain and damage response of a fiber reinforced composite laminated plate under transverse impact load is employed to demonstrate the application of this theory. In the example, the damage variable coupled with geometric large deformation of laminated plate is also considered. The calculating results illustrate the influence of damage on strain field in the impacted laminated plate.
Keywords: damage variable tensor; constitutive equations; composite laminated plates; transverse impact; strain response