聚氨酯泡沫铝动力学性能实验及本构模型研究

为了改进泡沫铝的动态吸能性能,将聚氨酯填充到开孔泡沫铝中制备成复合材料。通过霍普金森杆(SHPB)冲击实验,研究包含相对密度、应变、应变率和聚氨酯含量等影响因素的聚氨酯泡沫铝材料的动力学性能,并建立了动态本构模型。实验结果表明,聚氨酯泡沫铝的动态弹性模量与相对密度无关,屈服强度和流变应力与应变率和泡沫铝的相对密度成正比;聚氨酯泡沫铝的屈服强度与泡沫聚氨酯质量增加近似呈线性关系。所建立的动态本构模型在相对密度和应变率在一定的变化范围内与实验数据吻合较好。     

硬质聚氨酯泡沫塑料的缓冲吸能特性评估

在对泡沫塑料缓冲吸能特性评估的常用方法进行分析后，对四种密度硬质聚氨酯泡沫塑料在各种应变率下的缓冲吸能特性进行了评估，并介绍了本构关系在泡沫材料缓冲吸能特性评估中的应用。     

聚氨酯泡沫铝复合结构抗爆吸能试验及数值模拟分析

通过对聚氨酯泡沫铝和混凝土组成的复合结构进行接触爆炸试验,探讨了聚氨酯泡沫铝的吸能性能,并进行数值模拟分析。结果显示:聚氨酯泡沫铝的吸能性能明显优于泡沫铝,吸能层厚度对吸能效果影响很大,多层结构的聚氨酯泡沫铝吸能性能对比厚度一致的单层吸能层结构没有明显的改善;在保证了比较合理的吸能层厚度后,防护结构的每一层材料层存在着一个最佳的厚度组合来保证复合层优良的抗爆性能。     

软质聚氨酯泡沫的动态压缩力学性能和本构模型

采用Instron 9350落锤试验机研究了中低应变率下软质聚氨酯泡沫的动态压缩力学性能,分析了其应力-应变响应特征和应变率敏感性,讨论了应变率对材料应变率敏感性指数和能量吸收特性的影响,并基于实验结果建立了可准确描述其压缩力学响应的率相关本构模型。结果表明,软质聚氨酯泡沫的静动态压缩应力-应变响应具有典型的三阶段特征,且呈现出明显的应变率强化效应。准静态加载下,材料具有较高的吸能效率但能量吸收值较小,应变率对最大吸能效率和比吸能的影响较小;动态加载下,随着应变率的增加,最大吸能效率显著减小而比吸能明显增大。考虑应变率影响的修正Sherwood-Frost模型和修正Avalle模型都能够很好地表征软质聚氨酯泡沫的静动态压缩应力-应变响应,但修正Avalle模型的参数较少,更便于工程应用。研究结果可为软质聚氨酯泡沫抗冲击结构的设计和优化提供指导。     

泡沫铝缓冲吸能评估及其特性

对泡沫铝缓冲吸能特性的评估方法进行了比较分析 ,明确了吸能效率曲线与理想吸能效率曲线的应用范围 ,为缓冲器的选材与设计提供了依据。同时还对四种密度的泡沫铝在动静态下的缓冲吸能特性进行了评估 ,研究表明 ,泡沫铝是一种优良的吸能材料。     

硬质聚氨酯泡沫塑料隔爆性能的研究

对四种不同密度的硬质聚氨酯泡沫塑料（简称ＲＰＵＦ）隔爆性能进行了研究。发现随着ＲＰＵＦ材料密度的增加，其被发雷管爆炸概率为５０％时的隔板厚度不断下降。对密度为０．０９１和０．３４５ｇ／ｃｍ３的ＲＰＵＦ材料作了静态压缩及动态冲击压缩试验（应变率为１０３ｓ－１）。结果表明此材料具有较好的吸能缓冲性能，并且在所研究的密度范围内，随着密度的增加，材料的吸能缓冲性能增加，隔爆性能也增强。     

泡沫铝填充金属薄壁圆管的实验和理论研究

利用实验研究与理论分析相结合的方法研究了泡沫铝填充金属薄壁圆管在准静态侧向压缩下的力学响应.基于能量法,建立了泡沫铝填充圆管和金属薄壁圆管在侧向均匀压缩时的瞬时侧向力、平均侧向力和总吸能的理论公式.对泡沫铝填充管与金属薄壁圆管进行了准静态侧向压缩实验,并且将实验结果与理论公式进行了对比,结果表明理论预测值与实验结果吻合较好.基于建立的理论分析模型,研究了管的几何尺寸以及泡沫铝材料的密度对结构的瞬时侧向力、平均侧向力、总吸能和比吸能的影响.结果表明,在准静态侧向压缩下,泡沫铝填充管的总吸能大于对应的金属薄壁圆管;泡沫铝填充管的侧向压缩力和总吸能随管长度、壁厚和直径的增加而增大;当填充材料泡沫铝密度增大时,填充管的总吸能与侧向压缩力均增加.     

不同孔隙率及孔径泡沫铝的力学与吸能特性研究

对三种孔径两种孔隙率共六种泡沫铝试件进行了静态压缩试验,发现对于中孔隙率材料,孔隙率对材料力学性能和吸能性能仍有明显影响:孔隙率越大,其吸能能力越强,但是屈服极限越小.孔径对材料吸能能力也有一定影响.同时,试验中还发现,对于孔隙率为55%的材料,当孔径≤1mm时,泡沫铝材料的孔径对其力学性能及吸能性能影响甚小.     

含金属微粉泡沫材料中爆炸波衰减规律实验研究

设计并制备了一种新型的聚氨酯泡沫材料,研究了爆炸波在该材料中的衰减规律.材料的主要设计原理是在聚氨酯材料中均匀混合了10μm量级的金属微粉,以提高骨架的吸热能力,从而提高其抗爆性能.搭建了实验平台并分别测量了爆炸波在相同孔隙率下含金属微粉和不含金属微粉的聚氨酯材料,同时测量了不同金属微粉含量的聚氨酯材料中的传播特性.实验结果表明:含金属微粉的聚氨酯材料具有更好的抗爆性能.     

泡沫铝铜合金静态压缩力学行为和吸能性能的实验研究

通过静态压缩实验研究一种新型闭孔泡沫铝材料泡沫铝铜合金的静态压缩力学行为和吸能性能。对实验得到的一定密度范围内的材料的弹性模量E和平台应力pl关于相对密度进行曲线拟合,发现将Gibson等给出的开孔泡沫理论公式中的幂次常数修正为由实验确定的常数,可以给出一定密度范围的闭孔泡沫铝铜合金材料的弹性模量和平台应力与相对密度之间关系的一个较好的估计。采用比能-应力或比能-应变曲线,可以对不同密度的泡沫铝铜合金材料的吸能情况进行较为直观的比较和分析。该曲线对工程设计具有较好的指导意义。     

空心微珠/Al复合材料的动态压缩力学性能和吸能特性

利用分离式霍普金森压杆（split Hopkinson pressure bar,SHPB）系统对空心微珠体积分数为0.4的空心微珠/1199Al复合泡沫在1 700~2 900s-1应变率范围内的动态压缩力学性能、吸能性能进行了研究,还利用SEM扫描电镜对压缩试件断口进行微观组织分析,与准静态条件下材料的压缩力学性能及压缩变形机制进行了对比。结果表明,空心微珠/1199Al复合泡沫是一种应变率敏感材料,与准静态结果相比,在高应变率下复合材料的流动应力和塑性应变有明显的增大,应变率硬化效应对复合材料的流动应力的影响明显大于应变硬化的影响。复合材料的准静态和动态压缩变形机制存在一定差异,动态载荷作用下,空心微珠/1199Al复合泡沫内部空心微珠的压缩和基体材料的充填同时发生,组分之间具有良好的协调变形能力。     

Aluminum foam-polymer hybrid structures (APM aluminum foam) in compression testing

The Advanced Pore Morphology (APM) process, a new method for production of aluminum foam-polymer hybrid materials, is described. Small volume aluminum foam spheres are produced first and then adhesively joined in a separate process step to realize an APM foam part. Detailed information on mechanical properties of this new hybrid material is given. Results of uniaxial and hydrostatic compression tests are summarized and evaluated to show how typical parameters characterizing material and process such as spatial arrangement, size and density of the foam elements influence the global properties. Two levels of the hierarchical architecture of the material are evaluated—namely the individual foam spheres and the hybrid structure. Variation of adhesives and adhesive coating thickness used in bonding the spheres in conjunction with study of unbonded specimens provides additional insight in the influence of this bond. First estimates on density dependence of mechanical properties are derived from the experimental data. Distinctive differences between APM and conventional aluminum foams are qualitatively explained. Throughout the study, AlSi7 aluminum foam produced from chemically identical precursor material according to the powder metallurgical FOAMINAL^® process is included as reference material.     

泡沫金属缓冲器的设计新方法及应用

根据泡沫材料的动态特性,采用最佳吸能效率图取代吸能图的方法,进行泡沫金属缓冲器设计。比较表明这种方法是合理的,具有更好的通用性与操作性。以泡沫铝为例,具体阐述了最佳吸能图在泡沫铝缓冲器优化设计中的应用。     

Effects of Seawater and Low Temperatures on Polymeric Foam Core Material

Polymeric composite sandwich structures, often manufactured using a thick foam core material and thin composite facings, are of significant interest in naval applications. This paper summarizes the coupled effect of sea water and low temperature on the mechanical properties of closed cell polymeric H100 foam core material. The study considers the effects of harsh sea environmental conditions on the fracture and deformation behavior of such a foam material under complex loading conditions that include tension, torsion, compression, and true-triaxial stress paths. Mechanical testing techniques are developed using coupon samples of suitable geometry that minimize grip effects on these low density complex foam materials, along with information associated with the observed cross-anisotropic behavior. Interfacial delamination fracture response for the sandwich structures due to the combined effects of sea water and low temperature are evaluated and the associated degradation in critical energy release rate for delamination is found to be substantial. Experimental data for H100 foam cores associated with moisture induced expansional strains are also included.     

硬质聚氨酯泡沫力学特性的静水压力加载实验方法研究

泡沫材料在多轴载荷下的力学性能是工程中非常关心的问题。利用土壤的三轴压缩试验装置,通过试验方法的改进,提出了一种体应变测定和修正的方法,对硬质聚氨酯泡沫材料的静水压力特性进行了研究,得到了一些有价值的数据和结论。研究表明:在准静态静水压加载条件下,该材料的应力-应变曲线明显地分为弹性段、塑性段和压实段,且屈服强度比单向压缩时略大、压实应变略小。最后通过不同高度的试样对比试验,对聚氨酯泡沫材料的不均匀变形和弯曲的原因进行了分析和比较,指出了试验时应该注意的问题。     

Insight into the physics of foam densification via numerical simulation

Foamed materials are increasingly finding application in engineering systems on account of their unique properties. The basic mechanics which gives rise to these properties is well established, they are the result of collapsing the foam microstructure. Despite a basic understanding, the relationship between the details of foam microstructure and foam bulk response is generally unknown. With continued advances in computational power, many researchers have turned to numerical simulation to gain insight into the relationship between foam microstructure and bulk properties. However, numerical simulation of foam microscale deformation is a very challenging computational task and, to date, simulations over the full range of bulk deformations in which these materials operate have not been reported. Here a particle technique is demonstrated to be well-suited for this computational challenge, permitting simulation of the compression of foam microstructures to full densification. Computations on idealized foam microstructures are in agreement with engineering guidelines and various experimental results. Dependencies on degree of microstructure regularity and material properties are demonstrated. A surprising amount of porosity is found in fully-densified foams. The presence of residual porosity can strongly influence dynamic material response and hence needs to be accounted for in bulk (average) constitutive models of these materials.     

泡沫铝的单向力学行为

本文对不同孔径的开孔泡沫铝材料的单向拉伸性能和单向压缩性能进行了研究,揭示了泡沫铝材料的变形机理,并且发现相对密度不是确定材料力学属性的唯一参数,孔径大小对材料的力学性能也有一定的影响。基于实验数据,我们讨论了材料的宏观力学性能和微观结构的联系,并利用Ramberg-Osgood模型描述了材料的单轴拉伸一维应力应变关系。     

复合泡沫塑料力学行为的研究综述

复合泡沫塑料是一种重要的防护材料,它在国防工业和民用工业各部门均有许多重要的应用,对这类材料的力学行为进行研究具有重要的学术价值和应用前景.本文对复合泡沫塑料力学行为的研究文献进行了综述.首先,对复合泡沫塑料力学行为研究的早期工作进行了简介.然后,重点介绍了复合泡沫塑料力学行为研究的最新进展,其中也包括作者近期在该领域开展的一些工作;对复合泡沫塑料进行了静、动态压缩实验和细观加载实验,研究了材料的宏观变形规律和细观失效机制;在理论研究方面,探讨了复合泡沫塑料的能量吸收和缓冲特性,从宏、细观力学分析出发研究了复合泡沫塑料有关力学性能的理论预测问题;还利用计算机和通用软件对高密度复合泡沫塑料进行了有限元分析,研究了高密度复合泡沫塑料的失效行为.最后,给出对该领域研究工作的一些展望.      

Modeling the dynamic response of visco-elastic open-cell foams

This article introduces a mesoscopic formulation for modeling the dynamic response of visco-elastic, open-cell solid foams. The effective material response is obtained by enforcing on a representative 3D unit cell the principle of minimum action for dissipative systems. The resulting model accounts explicitly for the foam topology, the elastic and viscous properties of the cell wall, and the inertial effects arising from non-affine motion within the cells. The microinertial effects become significant in retarding the foam collapse during exceedingly high strain-rate loading. As an application example, a heterogenous case of compressive deformation at high strain rate is simulated utilizing the present model as a constitutive update in a non-linear finite element analysis code. This FEM simulation shows the ability of the model to capture the progressive foam collapse during the dynamic compression as observed in experimental studies. Using the microscopic model, the inertial and viscous strain-rate effects are investigated through the foam density, viscosity, and relative density. Based on the physics incorporated into the local cell model, we provide insight into the physical mechanisms responsible for the experimentally observed strain-rate effects on the behavior of dynamically loaded foam materials.     

Development of the polymeric split hopkinson bar technique

A compression version of the split Hopkinson bar with pressure bars and a striker, which are made of Plexiglas (a material with low density and velocity of sound) is developed. The technique is designed to determine stress—strain diagrams under high strain rates of highly deformable materials with low density and strength, such as plastics, foams, and rubbers. Dynamic stress—strain curves in compression for spheroplastic, foam plastic, and rubber are presented, which were obtained using the technique developed.