Tailored Fibre Placement (TFP) is a textile process for the production of fibre reinforced structures. Using TFP the carbon fibre rovings may be placed on a base material in almost any desired orientation, thus deploying calculated optimum fibre quantities and orientations for optimal performance. In common composite structures the anisotropic material properties are usually not fully exploited. Stress concentration at notches, edges and cut-outs are critical in view of the material failure behaviour in a structure. While in isotropic structures only a shape optimization is possible to reduce local stress concentrations, in orthotropic and composite structures an orientation of the fibres appropriate to the local stress condition can be used as an additional local design variable for strength and stiffness optimization.
To support the TFP-technology the Institute of Composite Structures and Adaptive Systems has two fields of activity:
1. Developement of the tool TACO (TAilored COmposite Design Code)
The tool TACO (Tailored Composite Design Code) was developed to optimize complex composite structures and it is embedded in the MSC PATRAN / NASTRAN environment. As optimization criterion the two-dimensional CAIO formulation was adapted: The tool changes the fibre orientations within a user-defined layer of a finite-element (FE) model such that the fibres are as closely aligned to the direction of the principal stresses as possible. As result of this procedure the shear stress and the corresponding failure response is reduced. A challenging problem in the analysis of the anisotropic mechanical properties of composites has been the development of adequate failure criteria. For failure analysis the so called Simple Parabolic Criterion (SPC) was implemented, which is able to distinguish between fibre fracture and inter fibre fracture as different failure modes.
2. Application of TACO
The application of TACO allows an optimized design for a specific composite light-weight-component. It aims to fully exploit the uniaxial material properties, leads to a local reinforcement and a more efficient load transfer and improves the fracture behaviour. Main area of application are uniaxial loaded laminate structures with a limited number of load cases. A typical application is an open-hole plate under unidirectional tensile loading.