The light polymer composite materials with carbon tri-axially reinforcement have been successfully used for fan cases in several jet engine design. Fan case containment must resist blade impact, so failure behavior during high velocity impact is very important. The expensive and time consuming blade-out tests are required by FAA. Both industry and government would like to use realistic numerical simulations of the blade-out events in order to understand the physics of failure and help in the design process. This study describes ability to simulate failure of carbon reinforced tri-axial composite materials used for such jet engine fan cases. The objective of this work is to predict threshold velocities for different fiber orientation in braided tri-axial composite half cylinders impacted by soft projectiles.
The simplified braided through thickness integration point methodology was used to simulate impact event of tri-axial braided composite using LsDyna3D nonlinear FE code. This method is based on unit cell consisting of sub-cells that are modeled by shell elements with local lamination structure. Each integration point of shell element represents different laminae with local fiber orientation.
Composite laminate is represented using standard material model Mat_54 (ENHANCED_COMPOSITE_DDAMAGE), and soft projectile is represented by Mat_181 (SIMPLIFIED_RUBBER). Impact simulation was validated using experimental test results conducted at NASA Ballistic Impact Laboratory for [0°/±60°] fiber orientation braid. The model parameters were chosen so threshold velocity and damage shape of the simulation correlates well with experimental observations.
The results of parametric studies show that the local minima of threshold velocities are for [0°/±15°] and [0°/±70°] degrees braid and the largest threshold velocity is obtained for the braid with fiber orientation between [0°/±40°]and [0°/±45°]. So the jet engine cases should be fabricated using [0°/±45°] braid.