Coated Fabric Airbag Simulation via Dynamic Slave Elements
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Solution Overview
Problem
Current computer-aided engineering analysis methods, such as finite element analysis, are inefficient for simulating the structural behavior of airbags made of coated fabric due to the lack of bending stiffness, leading to excessive folding and increased computation time and costs.
Innovation Solution
A special purpose finite element is introduced, comprising a membrane element and a pair of dynamically configured slave elements that provide additional bending resistance, allowing for accurate simulation of coated fabric airbags without requiring extra bending degrees-of-freedom, by updating nodal locations based on averaged nodal normal vectors and fabric thickness.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If conventional shell finite elements with modifications to bending terms or adding weak shell element are used to capture bending resistance of coated fabric, then the bending resistance is improved, but computation time and costs double compared to membrane element model
Solution Approach 1:
The finite element model is segmented into two distinct parts: membrane elements that represent the fabric structure and slave elements that represent the coating layer. This segmentation allows each component to be modeled with appropriate properties while maintaining computational efficiency, as the slave elements only provide bending resistance without requiring full shell element complexity
Solution Approach 2:
Slave elements act as intermediaries that transfer bending resistance from the coating layer to the membrane elements. These slave elements are dynamically configured and connected to membrane elements, providing the necessary bending stiffness without requiring modifications to the membrane element formulation or using computationally intensive shell elements
2Productivity
If membrane elements are used to represent airbag, then the model is computationally efficient, but the simulated airbag has higher tendency of folding due to lack of bending stiffness
Solution Approach 1:
The model applies different properties to different parts of the system: membrane elements provide computational efficiency for the fabric structure while slave elements provide localized bending resistance where needed. This local quality approach allows the membrane elements to remain computationally efficient while the slave elements compensate for the lack of bending stiffness in specific locations
Solution Approach 2:
The finite element model uses a composite structure combining membrane elements and slave elements, analogous to the composite nature of coated fabric (fabric substrate + coating layer). This composite modeling approach captures the bending resistance of the coated fabric while maintaining the computational efficiency of membrane elements
Data Source
AI summary
Methods of numerically simulating structural behaviors of airbag made of coated fabric material are disclosed. A special purpose finite element is configured to include a membrane element and a pair of dynamically configured slave elements, which provides additional bending resistance of the coated fabric material. At each solution cycle of a time-marching simulation, nodal locations of the slave elements are updated from corresponding averaged nodal normal vector, fabric thickness and coating thickness of the coated fabric material. The averaged nodal normal vector of a particular node is an average of element normal vector of those membrane elements connected to that particular node. Respective nodal locations are offset at a distance at either side of the corresponding node of the membrane element along the averaged normal vector. Using updated nodal locations, strains and stresses of the slave elements are obtained and then converted to internal nodal forces for additional bending resistance.