Dynamic Behaviour of Multiphase Media under High-Strain-Rate Loading

我提出的研究计划调查高应变率加载下的多相材料的动态响应，侧重于在散装材料的响应上的非均匀性的介观变化的作用。该计划包括与两种类型的多相材料有关的推进领域，特别是i）泡沫和ii）颗粒掺杂弹性体。研究方法将主要是实验性的，但计算研究将补充所有实验工作。该研究计划的长期目标概括为：·推进对脉冲载荷下多相材料响应的基本理解。·研究和模拟多尺度物理效应，特别是中尺度变化对多相和多材料系统的散装材料行为的影响。·开发和应用与冲击和爆炸波载荷下多相材料的高应变率测试相关的新实验方法。·将新的制造技术和创新的优化方法应用于防护设备中的材料设计。·培养高应变率变形领域的下一代科学家和工程师。拟议的研究计划的实际目标主要涉及应用于防护设备设计的先进材料的开发。这些材料与一系列商业应用相关，从体育器材和防弹保护到汽车和工业安全。研究计划的多学科性质和广泛的适用性确保了HQP的有效培训。在拟议的重点领域的研究工作概述如下：㈠泡沫由于其能量吸收能力而广泛用于个人和结构保护应用。近年来，人们对开发新材料的兴趣日益增加，以提供对广泛的潜在危险的上级保护，例如常见的与运动有关的冲击或对爆炸引起的冲击波的保护。该研究计划是开发各种性能分级的泡沫，这些泡沫经过优化以降低传递到受保护主体的应力水平。这将通过改变样品厚度的实际泡沫材料及其密度（孔隙率控制）来实现。从几种材料生产泡沫在材料特性方面比单独的密度分级提供更大的参数可变性。这些泡沫将使用增材制造技术生产，并将在准静态和高应变率载荷下进行测试。调查的重点是关于应力衰减的材料分级方法的有效性。ii）掺杂有硬夹杂物的环氧树脂已经发现作为高强度间隙组分的应用。在环氧树脂或弹性体中加入体积分数为5-30%的夹杂物，在准静态测试中可显著增强介质。实验证据表明，聚合的颗粒悬浮液应当提供优于防弹织物的其它间隙添加剂（例如剪切增稠流体）的上级防弹性能。掺杂弹性体的动态和失效行为，其中的时间尺度已被证明是强烈的夹杂物的大小依赖，将在不同的应变速率进行研究，以确定夹杂物体积分数的影响。这项工作的实际应用涉及混合防护织物的设计，该混合防护织物将陶瓷颗粒结合在聚合基质中，可以提供上级弹道、刺伤和一般撕裂保护。

My proposed research program investigates the dynamic response of multiphase materials under high-strain-rate loading, focusing on the role of mesoscopic variations in heterogeneity on the response of the bulk materials. This program is comprised of thrust areas pertaining to two types of multiphase materials, specifically i) foams and ii) particle-doped elastomers. The research approach will be primarily experimental, however computational investigations will complement all experimental work. The long-term objectives of the research program are summarized as: • advancing the fundamental understanding of multiphase material response under impulsive loading. • investigating and modeling multi-scale physical effects, particularly the effect of mesoscale variations on the bulk material behaviour of multiphase and multi-material systems. • develop and apply new experimental methodologies related to high-strain-rate testing of multiphase materials under impact and blast wave loading. • apply new manufacturing technologies and innovative optimization approaches to the design of materials with applications in protective equipment. • train the next generation of scientists and engineers in the area of high-strain-rate deformation. The practical objectives of the proposed research program pertain primarily to the development of advanced materials applied to the design of protective equipment. These materials are relevant to a range of commercial applications from sporting equipment and ballistic protection to automotive and industrial safety. The multidisciplinary nature of the research plan and broad applicability ensures effective training of HQP. A summary of research efforts in the proposed thrust areas is as follows: i) Foams are used extensively in personal and structural protective applications due to their energy absorption capabilities. In recent years, there has been an increased interest in the development of new materials to provide superior protection from a wide range of potential dangers, such as common sport-related impacts or protection from blast waves due to an explosion. The research plan is to develop a variety of property-graded foams that are optimized to reduce the levels of stress transferred to a protected body. This will be accomplished by varying the actual foam materials through the thickness of the samples as well as their density (porosity control). Producing a foam from several materials offers greater parametric variability in terms of material properties than density grading alone. The foams will be produced using additive manufacturing technologies and will be tested under quasi-static and high-strain-rate loading. The investigation focuses on the effectiveness of material grading approaches with regard to stress attenuation. ii) Epoxies doped with hard inclusions have found applications as high-strength interstitial components. The addition of inclusions to either epoxies or elastomers at volume fractions in the range of 5-30% has been shown to result in significant strengthening of the medium in quasi-static testing. The experimental evidence suggests that a polymerized particle suspension should provide superior ballistic performance over other interstitial additives to ballistic fabrics, such as shear thickening fluids. The dynamic and failure behaviour of doped elastomers, the timescale of which has been shown to be strongly inclusion-size dependent, will be investigated at various strain rates to determine the influenced of inclusion volume fraction. The practical application of this work relates to the design of hybrid protective fabrics incorporating ceramic particles in a polymerized matrix that can provide superior ballistic, stab, and general laceration protection.