Introducing composite lattice core sandwich structure as an alternative proposal for engine hood

Pedestrian protection capability is critical for lightweight design of automotive engine hood. Here, a novel and lightweight composite sandwich hood including two fiber reinforced composite panels and a lattice core was proposed and the corresponding pedestrian protection performance was evaluated via Head Injury Criterion (HIC). The novel double-curvature composite sandwich hood with a pyramidal lattice core was designed based on a commercialized product with a weight reduction by 25%, and fabricated using interlocking approach. A homogenized constitutive model was developed for the pyramidal lattice core and utilized in the following headform-to-hood impact simulations with LS-DYNA. The stiffer sandwich hood revealed better pedestrian safety performance compared with the corresponding baseline hood without lattice core where secondary collision happened. Also, effects of geometrical variables, material selection and core types were discussed. The variation of panel thickness played a more important role in the average HIC values compared with that of core geometries. Among various material selections, hoods designed with carbon fiber reinforced composite (CFRC) panels and a flax fiber reinforced composite (FFRC) lattice core achieved the minimum head injury. Additionally, lattice core outperformed traditional honeycomb and foam in sandwich hood design. The present study demonstrates the feasibility of employing lattice materials in lightweight design of hood and other car body coverage.