Development of lightweight composite helmet using auxetic materials

军用头盔的使用大大减少了受伤，挽救了许多士兵的生命。头盔的防护能力是根据两个主要测试指标来评估的：抗穿透性（RTP）和背面变形（BFD）。防弹头盔的设计考虑了许多因素，包括舒适度、重量、适合度和可维护性。特别是，由于长期作战，军用头盔的重量轻是非常重要的。在防护结构中普遍使用轻质复合材料，这对确保与金属材料相同的防护水平产生了巨大的挑战。开发更高效材料的不同方法引起了人们对增塑型结构的兴趣。辅助性是指负泊松比，这是一种超材料特性。因此，当压缩载荷被应用到一个auxetic，材料将收缩的方向正交于应用载荷，创建一个更密集的区域。这种致密化使助塑剂适合于剧烈的载荷条件，如冲击。这项研究计划将检验它们在设计轻质复合头盔方面的有效性。为了减少设计周期，确保满足安全设计标准，虚拟试验通常采用数值模拟的方式进行。虚拟冲击试验数据随后被用作新设计开发的一部分。这些数值模拟产生的结果不需要建立物理模型，并且可以相对快速和廉价地执行。这允许优化设计之前的头盔的实际原型必须建立。该项目的目的是开发一种使用辅助核心结构的最佳复合头盔，以提供最轻的军用头盔，提高弹道效率。本文将建立一种新的有限元模型来分析复合材料夹层板的冲击响应。头盔外壳材料、外壳厚度、冲击速度和冲击类型（半球形和扁平砧）对性能的影响也将被研究。”

The use of military helmets has greatly reduced injuries and saved lives of many soldiers. A helmet's protective capabilities are evaluated on the basis of two primary test measures: resistance to penetration (RTP) and back face deformation (BFD). Many factors are considered during ballistic helmet design, including comfort, weight, fit, and maintainability. Especially, being light in weight for military helmets is very important due to long-term operations. The ubiquitous use of lightweight composite materials in protective structures has created a formidable challenge in ensuring the same level of protectiveness as their metallic counterpart. Different approaches toward the development of more efficient materials have led to an interest in auxetic structures. Auxetic refers to a negative Poisson's ratio which is a meta-material property. Consequently, when a compressive load is applied to an auxetic, the material will contract in the direction orthogonal to the applied load, creating a denser region. This densification makes auxetics suited to severe loading conditions such as impact. This research programme will examine their effectiveness in the design of lightweight composite helmets.In order to decrease design cycle times and ensure that safe design standards are met, virtual tests are usually performed by numerical simulation. The virtual impact test data are subsequently used as part of the development of a new design. These numerical simulations produce results without building a physical model, and can be performed relatively quickly and inexpensively. This permits optimization of the design before an actual prototype of the helmet has to be built.The aim of this project is to develop an optimum composite helmet using auxetic core structure, to deliver the lightest possible military helmet with improved ballistic efficiency. A new finite element model will be developed to analyse the impact response of composite sandwich panels using auxetic cores. The effect of helmet shell material, shell thickness, impact velocities, and impact types (with hemispherical and flat anvils) on the performance will also be studied. "