Draping of engineered prepregs and reinforced thermoplastics
The aim of DEPART is to provide the fundamental understanding, materials
characterisation, and modeling tools for the draping and consolidation of fabric based composites.
A detailed understanding of the drape behaviour of woven fabrics is important to enable accurate predictions
of the mechanical properties of complex-shaped structures made from woven fabric and to optimise their
manufacture. One of the most important considerations facing a composites designer is understanding how the
fabric behaves as it is draped over the mould. Unidirectional material is difficult and time-consuming to
drape over curved structures, although it is precisely these curved geometries which use composite material
most efficiently. For this reason, materials based on either woven or stitch-bonded (non-crimp) fabrics are
generally used. As the fabric is draped, it can undergo large in-plane deformations, changing the fibre
orientation angles and the lamina thickness. These alterations in the fibre architecture have a significant
impact on the strength and stiffness of the final structure. In the most severe cases the material can
wrinkle or lose contact with the mould, severely reducing the quality of the finished product.
The DEPART project looks into the micromechanical analysis of the fabric shear deformation as well as the
simulation of the draping process of the composite.
In terms of drape simulation, the effort is to provide the basis for developing a drape model intermediate to
the two approaches used in the past: namely kinematic modelling (e.g. MSC Patran Laminate Modeler) and a
comprehensive finite element analysis (e.g. ESI PAM/FORM) of the drape process. The former approach, while
being simple, lacks the completeness and the accuracy due to omission of draping forces and detailed fabric
properties. The latter finite element approach of modelling fabric drape requires long processing times and a
large amount of input data. The 'next-generation' drape model expected to evolve from the work presented in
this paper aims to provide for the secondary effects of draping forces on the fabric deformation.
With the industrial partners from aerospace, automotive as well as CAD/CAE sectors, the project aims to
provide solutions with a wide range of applicability. Collaboration with the Nottingham University helps in
division of the goals into investigating the micro- or macro- mechanics of the composites separately. The
micromechanics expertise at Cambridge University provides an able platform to focus on the low-level fabric
deformations, tensile and compressive behaviours in both elastic and plastic regimes, and the drape
simulations taking these results into account. Industrial components supplied by DERA and BAE SYSTEMS provide
a basis to evaluate the accuracy and to identify the range of applicability of the draping/forming
simulations. The modeling tools are proposed to be implemented as part of MSC's Patran Laminate Modeler
To investigate draping behaviour for a component with less uniform curvature, the rear half of a helmet is
being used, and is shown below.
Fig 1. Draped pattern over the back-skin of DERA supplied helmet: output of Patran LM
- SB Sharma, MPF Sutcliffe, MJ Clifford and AC Long. 'Experimental investigation of tow deformation during
draping of woven fabrics', Proc. of 4th ESAFORM Conf. on Metal Forming, 23-25 April 2001, Liege, Belgium. (Abstract)
- SB Sharma, MPF Sutcliffe. 'Draping of woven composites over irregular surfaces', Proc. of Int. Conf. on
Composite Materials ICCM-13, 25-29 June 2001, Beijing, China. (Abstract)
Principal Investigator & Researchers
Engineering and Physical Sciences Research Council (EPSRC), Research
Industrial Partners and Educational Collaborators