Impact response of an origami-shaped composite crash box: Experimental analysis and numerical optimization

In this work, an investigation of the crush response of a simplified CFRP origami crash box subjected to axialimpact is proposed. Crash boxes are thin‐walled structural components of the vehicles designed to absorbenergy during impact events at low‐medium velocity. In particular, the crash boxes must guarantee a progres-sive and controlled energy absorption, avoiding peak of force (and thus acceleration) that can lead to passengerinjury. In recent years, crash boxes made of carbonfibre reinforced polymer (CFRP) have found application inthe automotive sector. However, their brittle failure mode leads to an irregular crushing trend characterized bypeak of force. Thereafter, the crushing behaviour of the composite material structures can be improved by mod-ifying their geometrical parameters. Among the most promising solutions, the origami structure is increasinglyconsidered for crash boxes. The origami crash box here considered consists of four axially stacked basic struc-tures. Each basic structure is composed of four trapezoidal faces and four triangular faces. The upper cross sec-tion is squared, whereas the lower cross section has an octagonal shape. The structural behaviour of theorigami component was investigated according to different sizes of the triangular faces. The numerical modelswere simulated with thefinite element commercial code LS‐Dyna in its explicit formulation. The optimal shapeof the origami structure in terms of maximum energy absorption and limited force peak was defined in LS‐OPTenvironment. The objective function of the shape optimization algorithm was set to maximize the energyabsorption, while limiting the peak of force. The optimal shape defined presented larger sizes in the top basicstructures than in the bottom parts, resulting in more inclined faces. The result suggested that more inclinedfaces in the top part can guarantee a fracture‐triggering effect in the crash box, which ensured a smaller peakforce.