Analytical modelling of delamination and kink banding in composite laminates

Research Team

• Professor Ahmer Wadee: Imperial College London
• Dr Christina Völlmecke: TU Berlin (former PhD student)
• Dr Stylianos Yiatros: Cyprus University of Technology (former PhD student)
• Mr Joseph Haley: Imperial College London

Background

Taking inspiration from earlier research work done at Imperial and the University of Bath, the investigation from analytical methods of the various failure modes seen in composites was undertaken. Firstly, composite plates with a pre-existing damaged region under axial compression was investigated [1-6]. A sequence of nonlinear models that accounted for static and propagating delaminations were formulated from finding approximate solutions of the von Kármán plate equations in conjunction with a cohesive zone model that assumed peeling fracture propagation (Mode I). This led to a series of studies where the type of instability behaviour, where local, global or mixed mode buckling, controlled the extent of any delamination growth [5].

Secondly, the possibility of kink banding in uni-directional fibre composites was investigated using techniques derived from the studies on the geological and other layered materials. Of course, for laminated composites the interlaminar matrix plays a key role in the mechanics of the deformation with a possibility of fracture propagation from a variety of modes. In turns out the dominant mode is shearing (Mode II) and the formulated model, which can be solved in closed form, matches previously published results very closely and has been reported in a special issue of Philosophical Transactions of the Royal Society A [7]. This work extended the link model work by investigating the fracture behaviour of the interlaminar matrix using analytical techniques and has involved collaboration with my former research students Christina Völlmecke, Stylianos Yiatros and the prize winning undergraduate student Joe Haley who studied this problem in his final year research project.

Context and Methodology

A combination of analytical techniques, including variational methods, the judicious use of discrete spring and link models together with computational aids such as Maple and Matlab were used intensively. Where necessary, the nonlinear bifurcation problems were solved in AUTO. 

Seminars and Conference Presentations

• June 2012
  Notre Dame, USA. ASCE/EMI Conference (EMI/PMC 2012 - Invited) 
• June 2011
  Boston, USA. ASCE/EMI Conference (EMI 2011)
• September 2010
  Cape Town, South Africa. 4th Structural Engineering, Mechanics and Computation Conference (SEMC 2010).
• June 2009
  Blacksburg, USA. Joint ASCE-ASME-SES conference on Mechanics and Materials (Invited).
• April 2009
  Phuket, Thailand. International conference on computational and experimental engineering and sciences (ICCES 2009).
• September 2008
  Braunscheig, Germany. 2nd international conference on buckling and postbuckling behaviour of composite laminated shell structures with COCOMAT workshop.

References

1. Völlmecke, C. and Wadee, M. A., 2008. Nonlinear buckling of uniaxially compressed delaminated composite panels, 2nd international conference on buckling and postbuckling behaviour of composite laminated shell structures with COCOMAT workshop.
2. Völlmecke, C. and Wadee, M. A., 2009. Buckling driven delamination in uniaxially compressed composite panels. In Chen, W., editor, Proceedings of the international conference on computational and experimental engineering and sciences, page 143. Mini-symposium on stability and collapse of composite shells.
3. Wadee, M. A. and Völlmecke, C. Analytical modelling of buckling driven delamination in composite plates. In Puri, I. K. and Hajj, M. R., editors, The joint ASCE-ASME-SES conference on mechanics and materials, pages 113–114, Blacksburg, USA, 2009. Invited contribution for symposium in honour of Zdenek Bazant.
4. Völlmecke, C. and Wadee M. A., 2010. Residual capacities of uniaxially compressed composite panels under buckling driven delamination. SEMC 2010: 4th International Conference on Structural Engineering, Mechanics and Computation, pp. 537-540, London: CRC.
5. Wadee, M. A. and Völlmecke C., 2011. Semi-analytical modelling of buckling driven delamination in uniaxially compressed damaged plates, IMA J. Appl. Math., 76(1):120-145.
6. Völlmecke, C., Yiatros, S. and Wadee M. A., 2011, Modelling the nonlinear elastic instability phenomena of laminated composite panels and sandwich structures, EMI2011: ASCE/EMI Conference, Boston, USA.
   Authors: Völlmecke C, Yiatros S, Wadee MA
   Abstract:
7. Wadee M. A., Völlmecke, C., Haley J. F. and Yiatros, S., 2012. Geometric modelling of kink banding in laminated structures, Phil. Trans. R. Soc. A 370(2137):1827-1849.

Doctoral Thesis

• Christina Völlmecke. Nonlinear buckling of delaminated panels. PhD thesis, Imperial College of Science, Technology and Medicine, 2010.