Microbuckle initiation from a patch of large amplitude fibre waviness in a composite under compression and bending

A finite element couple stress formulation is used to predict microbuckle initiation from a patch of fibre waviness in a unidirectional fibre composite under remote compression and bending. Attention is focused on the knock-down in strength due to large amplitude waviness, with the effects of the physical size of the imperfection included by incorporating the fibre bending resistance within the formulation. The predicted strengths devi ate significantly from the simpler kinking theory which neglects the role of fibre bending. Initial imperfections in the form of an infinite band and a circul ar wavy patch are considered: when these imperfections are of large spatial extent and possess a large misalignment angle, the compressive strength approximates the steady state band broadening stress for an infinite band. The effect of an imposed spatial gradient of stress within the composite is explored by determining the compressive strength of beams of finite height B for the loading cases of pure bending and axial compression. It is found that the compressive strength is sensitive to the magnitude of the imposed stress gradient: the compressive strength of the outer fibres of the beam in bending increases with diminishing height of the beam. This size dependence is much reduced for the case of uniform compression. © 2001 Editions scientifiques et medicales Elsevier SAS compressive strength / composites / finite elements / microbuckling

[1]  S. Kyriakides,et al.  On the axial propagation of kink bands in fiber composites : Part i experiments , 1999 .

[2]  S. Kyriakides,et al.  Initiation and axial propagation of kink bands in fiber composites , 1997 .

[3]  B. BIJUIANSKY,et al.  COMPRESSIVE FAILURE OF FIBRE COMPOSITES , 2002 .

[4]  N. Fleck,et al.  On kink-band propagation in fiber composites , 1998 .

[5]  Norman A. Fleck,et al.  Deformation and failure of a carbon fibre composite under combined shear and transverse loading , 1995 .

[6]  C. Shih,et al.  Kink band propagation and broadening in ductile matrix fiber composites: Experiments and analysis , 1998 .

[7]  N. Fleck,et al.  Prediction of compressive toughness for fibre composites , 1996, Proceedings of the Royal Society of London. Series A: Mathematical, Physical and Engineering Sciences.

[8]  Mpf Sutcliffe,et al.  A multiple field image analysis procedure for characterisation of fibre alignment in composites , 2001 .

[9]  M. Wisnom,et al.  Reduction in compressive strain to failure with increasing specimen size in pin-ended buckling tests , 1997 .

[10]  Norman A. Fleck,et al.  On the mechanics of braided composites in tension , 2000 .

[11]  N. Fleck,et al.  Microbuckle initiation from a hole and from the free edge of a fibre composite , 2000 .

[12]  Richard Schapery,et al.  Prediction of compressive strength and kink bands in composites using a work potential , 1995 .

[13]  B. W. Rosen,et al.  Mechanics of composite strengthening. , 1965 .

[14]  N. Fleck,et al.  Compressive Failure of Fibre Composites Due to Microbuckling , 1991 .

[15]  C. Shih,et al.  Kink band formation and band broadening in fiber composites under compressive loading , 1995 .

[16]  M. Wisnom.  On the High Compressive Strains Achieved in Bending Tests on Unidirectional Carbon Fibre-Epoxy , 1992 .

[17]  N. Fleck,et al.  Microbuckle initiation in fibre composites : A finite element study , 1995 .

[18]  N. Fleck,et al.  Prediction of Kink Width in Compressed Fiber Composites , 1995 .

[19]  Norman A. Fleck,et al.  Compressive Failure of Fiber Composites , 1997 .

[20]  Michael R Wisnom,et al.  The effect of fibre misalignment on the compressive strength of unidirectional carbon fibre/epoxy , 1990 .

[21]  S. Kyriakides,et al.  Aspects of the Failure and Postfailure of Fiber Composites in Compression , 1997 .

[22]  Stelios Kyriakides,et al.  On the compressive failure of fiber reinforced composites , 1995 .

[23]  N. Fleck,et al.  Microbuckle initiation in fibre composites under multiaxial loading , 1997, Proceedings of the Royal Society of London. Series A: Mathematical, Physical and Engineering Sciences.

[24]  Cv Clemens Verhoosel,et al.  Non-Linear Finite Element Analysis of Solids and Structures , 1991 .

[25]  Michael R Wisnom,et al.  The Effect of Fibre Waviness on the Relationship between Compressive and Flexural Strengths of Unidirectional Composites , 1994 .

[26]  S. Kyriakides,et al.  On the axial propagation of kink bands in fiber composites : Part ii analysis , 1999 .

[27]  Sumit Sharma.  Micromechanics , 1965, Nature.

[28]  Henrik Myhre Jensen,et al.  Analysis of compressive failure of layered materials by kink band broadening , 1999 .