A passenger vehicle hood is designed to meet Vulnerable Road User (VRU) regulatory requirements and consumer metric targets. Generally, hood inner design and its reinforcements, along with deformable space available under the hood are the main enablers to meet the Head Impact performance targets. However, cross functional balancing requirements, such as hood stiffness and packaging space constraints, can lead to higher Head Injury Criteria (HIC15) scores, particularly when secondary impacts are present. In such cases, a localized energy absorber is utilized to absorb the impact energy to reduce HIC within the target value. The current localized energy absorber solutions include the usage of flexible metal brackets, plastic absorbers etc. which have limited energy absorbing capacity and tuning capability. This paper focuses on usage of a novel 3D printed energy absorbers, based on various kinds of lattice structures. These absorbers are either sandwiched between the inner and the outer hood or are integrated directly with under hood parts such as shock tower or headlamp bolt locations to mitigate high HIC values.
The work focuses on virtual evaluation of Nylon-12 3D printed lattice designs, based on Body Centered Cubic (BCC) and Kelvin Lattice, for VRU energy management. These optimized lattice-based designs are shown to provide significant performance improvement over conventional energy absorbers. As 3D printing can support manufacturing of complex shapes, the lattice-based energy absorbers can be tuned easily to achieve optimal performance. Technological advancements in 3D printing make these solutions cost effective and easier to implement.