Luo Yunhua, Liang Zhaoyang
Department of Mechanical Engineering, Faculty of Engineering, University of Manitoba, Winnipeg, MB R3T 2N2, Canada.
Biomed Mater Eng. 2017;28(3):279-291. doi: 10.3233/BME-171674.
Understanding how a helmet protects the head, especially the soft brain tissues, is the prerequisite for improving helmet design. Intracranial pressure and stresses/strains in the brain tissues are the direct indicators of traumatic brain injury and they can be used to measure helmet performance. In this study, the effects of helmet design parameters such as the helmet shell stiffness, liner compliance and thickness on the brain injury indicators were investigated by virtual impact tests. A finite element head model (FEHM) was first constructed from medical images; a personally-fitted helmet made of composite material and foam was virtually prototyped using geometric information extracted from the FEHM; a helmet-head finite element model was then assembled. Virtual impact tests were conducted using the resulting helmet-head model. The obtained results suggested that, if the helmet shell already has adequate strength to resist excessive deformation and fracture, further increasing shell stiffness and strength would not considerably reduce intracranial pressure and brain strains; to reach the maximum protection with the available materials, the key is to effectively use the second stage in the stress-strain history of the liner foam material.
了解头盔如何保护头部，尤其是柔软的脑组织，是改进头盔设计的前提。颅内压力以及脑组织中的应力/应变是创伤性脑损伤的直接指标，可用于衡量头盔性能。在本研究中，通过虚拟撞击试验研究了头盔设计参数（如头盔外壳刚度、衬垫柔顺性和厚度）对脑损伤指标的影响。首先根据医学图像构建有限元头部模型（FEHM）；利用从FEHM中提取的几何信息，虚拟制作了一个由复合材料和泡沫制成的个性化定制头盔；然后组装了头盔-头部有限元模型。使用所得的头盔-头部模型进行虚拟撞击试验。获得的结果表明，如果头盔外壳已经具备足够的强度来抵抗过度变形和断裂，进一步提高外壳刚度和强度并不会显著降低颅内压力和脑部应变；为了用现有材料实现最大程度的保护，关键是要有效利用衬垫泡沫材料应力-应变历程中的第二阶段。
