Predicting wrinkles during forming of a 3K plain dry fabric material

Among various forming methods applicable to composite materials, Resin Transfer Molding (RTM) is suitable for thermosetting composites. RTM consists of two processes, the forming of dry fabric, then the impregnating and curing of the hardening resin matrix. Forming defects such as wrinkles and shear deformation in the first process may lead to problems including defective impregnation of resin and void generation. To prevent such problems, it is important at the design and fabrication stages to determine how to have minimal wrinkles and uniform shear deformation during the first process.

Use Cases Highlights

Simulation result accurately represents fine wrinkling during press forming

Effect of fiber direction on forming result

To evaluate the accuracy of the simulated result, a square cup drawing test of a single-layered CF dry fabric is performed with different fiber directions.

- Composite: CF dry fabric
- Lamination structure: Single layer
- Fiber direction[0°/90°] (top) vs. [+/-45°] (bottom)
- Evaluation item: Shear deformation angle, wrinkle location

Good consistency between the simulation result and the actual test was confirmed with the simulation reproducing the differences in forming behavior depending on the fiber direction.

Comparison of results: Actual test (left) and simulation (middle, right)

Reproducing fine wrinkling with different modeling methods

Stopping forming in mid-stroke, we can observe how wrinkles are formed. The result shows that accounting for out-of-plane shear deformation enables the Reissner-Mindlin shell theory based model to represent wrinkles with a small wavelength more accurately.

Reproduction of wrinkle with small wavelength