Aerospace components often incorporate complex structures such as multi-layer laminates or honeycomb sections. OnScale can use shell elements in arbitrary structured meshes to recreate these components to allow subtle effects such as delamination to be simulated.
The challenges of simulating carbon fibre laminates
The microstructure of composite structures significantly increases the complexity of simulating wave propagation: analytical and semi-analytical approaches no longer appropriate for most applications and transient FEA problems can become very large. OnScale is capable of running multi-billion element simulations, allowing scope to capture the necessary detail in the composite microstructure.
OnScale offers a variety of anisotropic material models that allow accurate simulation of Carbon Fibre Reinforced Plastic (CFRP) behaviour:
- Transversely isotropic materials: useful for simulating yarn bundles, and chopped strand matting
- Orthotropic materials: useful for simulating woven layers
- Fully anisotropic: useful for layers with complex weaves, using full stiffness tensor
The simulated honeycomb structure
Structures can be represented using a combination of continuum and shell elements, allowing great flexibility over the level of detail included in the simulation.
The modelled curved component material specifications:
- Hexcel IM7/8552 CFRP, 8 ply, unidirectional orientation, 1 mm thick
- 20 mm thick with 20 mm aluminum cells, 0.5 mm wall thickness
- 50 x 30 Cells (X by Y)
The excitation signal was a 20 kHz pulse applied as a pressure load on the top CFRP skin. The model was simulated in quarter symmetry with the outer surfaces at X-max and Y-max fixed.
In NDT, where bulk wave propagation dominates, individual yarn bundles will scatter sound and can have an impact on the inspection. At lower frequencies where surface waves dominate, it may be appropriate to approximate the structure as a series of layers or shell elements. Using shell elements also avoids the issue of drastically decreasing the simulation timestep when modelling thin structures which will increase runtime.
OnScale also allows custom meshes to be created for complex shapes and curved geometries to be accurately represented in simulation.
The simulation produces a number of useful outputs, including:
- Animations of the wave propagation paths through the component to understand where reflections may be coming from
- Analysis of various metrics over time such as velocities, displacements, stresses and strains at any point on the component
The video shows a pressure load applied to the top Carbon Fibre Reinforced Polymer (CFRP) skin layer on a curved aluminium honeycomb structure. The plot of velocity magnitude (z-component) allows the propagation of the wave through a non-defective component to be visualised.
You can read much more about simulating composite materials in our latest whitepaper Simulation of Ultrasonic Non-Destructive Testing of Composite Materials.