Experimental research of energy absorbing structures within helmet samples made with the additive manufacturing method - preliminary study.

PURPOSE: This study aimed to develop an energy-absorbing structure for bicycle helmets to minimize head injuries caused by collisions. The research team explored three geometric structures produced through additive methods and compares their energy absorption properties with a standard bicycle helmet made of Expanded Polystyrene (EPS) foam. METHODS: The study prepared samples of three geometric structures (a ball, a honeycomb and a conical shape) and a fragment of a bicycle helmet made of EPS foam with the same overall dimensions. Laboratory tests were conducted using a pneumatic hammer, piston compressor, anvil, triaxial accelerometer and data processing systems. Three crash tests were performed for each type of structure, and the anvil's maximum acceleration and stopping distance after the crash were analyzed. RESULTS: The study found that the energy absorption properties of the Polylactic Acid (PLA) material printed with the incremental method were comparable or better than those of the EPS material used in helmets. The geometric structure of the energy-absorbing material played a crucial role in its effectiveness. The most promising results were obtained for the ball samples. CONCLUSIONS: The study concluded that further research on energy-absorbing structures made using the Fused Deposition Modeling (FDM) method could be useful in the production of bicycle helmets. The results show that the geometric structure of the energy-absorbing material is a crucial factor in its effectiveness. The findings suggest that the ballshaped structure made with PLA material printed using the incremental method could be a promising design for bicycle helmets to minimize head injuries caused by collisions.

Rib kinematics analysis in oblique and lateral impact tests.

PURPOSE: Understanding thorax kinematics and rib breaking mechanisms in conditions of oblique and lateral impact is crucial in safety systems development. To increase knowledge level on this subject, simulation and experimental tests are necessary. The purpose of this study was to obtain single rib kinematics in the case of oblique and lateral impact conditions using numerical simulation approach. METHODS: Two impact tests using human body model of a 50th percentile man (THUMS v4.0.1 AM50) were performed in LS-Dyna R7.1.1. Impactor was a rigid cylinder with a diameter of 152 mm, and velocity equal to 6.7 m/s. Impact angle measured to sagittal plane was 30 and 90°, respectively in oblique and lateral impact case. RESULTS: Kinematics of ribs from 3rd to 6th were analyzed. Results shown significant similarities between oblique impact and kinematics of ribs tested in frontal impact conditions in the literature, with maximal costochondral joint displacement relatively to costovertebral joint varying from 65.4 mm (3rd rib) to 82.0 mm (5th rib). Deformation of rib in lateral impact conditions was different than during oblique impact test, with distinctive "flattening" approximately in the middle of the rib. Maximal relative displacement varies from 16.4 mm (6th rib) to 26.6 mm (5th rib) and its location depends on the analyzed rib. CONCLUSIONS: Oblique impact scenario may be simulated for the single rib on an experimental way using set-up of the frontal impact. Experimental simulation of the lateral impact for the single rib should not use the same set-up, as the kinematics analysis showed significant differences between simulated cases.