Dynamic bending response of double cylindrical tubes filled with aluminum foam

The dynamic three-point bending behavior of double cylindrical tubes filled with closed-cell aluminum foam core was studied experimentally and numerically. It is found that the deformation mode of this new structure under impact loading is different to that under quasi-static loading. The load carrying capacity of the structure subjected to impact remains at the level of that in the quasi-static situation. Compared with traditional foam-filled single tubes, the specific energy absorption efficiency of this new structure is much higher, and that of both foam-filled structures in the dynamic situation are higher than that in static situation. A preliminary experimental study on the effect of profiles and span of the structure were performed, and the result shows that these parameters affect the structure together. Numerical simulation of the bending behavior was also executed with the explicit finite element method. The mechanism of the dynamic response is revealed by comparison of the maximum strain history in the simulation.     

Design and manufacturing of anti-intrusion bars made of aluminium foam filled tubes

The role of an anti-intrusion bar for automotive use is to absorb the kinetic energy of the colliding vehicles that is partially converted into internal work of the members involved in the crash. The aim of this paper is to investigate the performances of anti-intrusion bars, made by tubes filled with aluminium foams. The reason for using a cellular material as a filler deals with its capacity to absorb energy during plastic deformation, while being lightweight. The study is mainly conducted by evaluating some key technical issues of the manufacturing problem and by running experimental and numerical analyses. The evaluation of materials and shapes of the closed sections to be filled is made in the perspective of a car manufacturer (production costs, weight reduction, space availability in a car door, etc.). Experimentally, foams are produced starting from an industrial aluminium precursor with a TiH₂ blowing agent. Empty and foam filled tubes are tested in three point bending, in order to evaluate their performances in terms of several performance parameters. Different manufacturing conditions, geometries and tube materials are investigated. The option of using hydroformed tubes, with non constant cross section, for the production of foam filled side structures id also discussed.     

Development of rubberized syntactic foam

This study explored a novel hybrid syntactic foam for composite sandwich structures. A unique microstructure was designed and realized. The hybrid foam was fabricated by dispersing styrene–butadiene rubber latex coated glass microballoons into a nanoclay and milled glass fiber reinforced epoxy matrix. The manufacturing process for developing this unique microstructure was developed. A total of seven groups of beam specimens with varying compositions were prepared. Each group contained 12 identical specimens with dimensions 304.8 mm × 50.8 mm × 15.2 mm. The total number of specimens was 84. Among them, 42 beams were pure foam core specimens and the remaining 42 beams were sandwich specimens with each foam core wrapped by two layers of E-glass plain woven fabric reinforced epoxy skin. Both low velocity impact tests and four-point bending tests were conducted on the foam cores and sandwich beams. Compared with the control specimens, the test results showed that the rubberized syntactic foams were able to absorb a considerably higher amount of impact energy with an insignificant sacrifice in strength. This multi-phase material contained structures bridging over several length-scales. SEM pictures showed that several mechanisms were activated to collaboratively absorb impact energy, including microballoon crushing, interfacial debonding, matrix microcracking, and fiber pull-out; the rubber layer and the microfibers prevented the microcracks from propagating into macroscopic damage by means of rubber pinning and fiber bridge-over mechanisms. The micro-length scale damage insured that the sandwich beams retained the majority of their strength after the impact.     

粉煤灰空心球/Al复合泡沫材料准静态力学性能及本构模型

为研究粉煤灰空心球/Al(Fly ash cenosphere/aluminum syntactic foam,FAC/Al)复合泡沫材料静力性能,采用万能试验机对铝基复合泡沫材料进行了准静态轴向压缩性能试验,考察了不同空心球平均粒径(分别为150、200和300μm)对铝基复合泡沫材料变形失效模式及力学性能的影响,并...     

Shear properties of CMB syntactic foam

In this research, a triaxial shear test is used as a means to provide yield surface data as well as other strength characteristics for carbon microballoon (CMB) syntactic foam. Additionally, pure shear tests and tensile tests are used to probe areas of this stress space not included in the triaxial shear tests. The data are used to characterize the material’s yield strength in stress space. The determined yield surface, the strain and other deformational behavior characteristics provide the necessary information for an accurate model and engineering design. The CMB foam specimens were divided into two sets: one with Thornel pitch-based carbon fibers and one without; both use Kerimid 601 as the binder. The CMB syntactic foam with fibers exhibited lower shear strength than the CMB syntactic foam without fibers. This is evident not only in the determined shear envelopes but also in the values obtained for the hydrostatic yield of both foams. Complementary analysis of the blending process of mixing fibers with CMB has been shown to destroy the microballoons and thus reduce the foams strength. The consequences of incorporating alternative materials can be verified with further testing.     

泡沫铝填充薄壁铝合金方管轴向压缩性能的数值模拟

泡沫铝填充薄壁结构的应用日趋广泛,研究了泡沫铝填充薄壁铝合金方管准静态轴向压缩条件下的力学性能。实验选用铝合金方管作为面板,Al-Mg合金泡沫铝作为夹芯制备泡沫铝填充薄壁铝合金方管。结果表明泡沫铝层合方管与薄壁铝合金方管的变形模式相同,都为对称叠缩变形模式,而且层合方管产生的折叠数比薄壁铝合金方管多。填充泡沫铝后,层合方管承受压力的能力也大大提高。采用ABAQUS软件建立了薄壁铝合金方管的有限元模型进行数值模拟,并且与相应的实验结果作对比,结果表明数值模拟与实验结果基本吻合。     

Experimental studies on the quasi-static bending behavior of double square tubes filled with aluminum foam

Quasi-static experiments were performed on empty tubes and aluminum foam-filled single and double tubes to study the effects of different filler arrangements on their three-point bending behavior. The load-carrying capacity and energy absorption of different structures are compared. The results confirm the advantage of the foam-filled structures. In particular, the double tube structure with aluminum foam filler enhances the load-carrying capacity, crashworthiness, and total and specific energy absorptions of the structure, in comparison with the foam-filled single tube. It was also found that increasing the wall thickness of the inner tube improves the performance of the structure within the experimental range, and adhesion between foam and tube has a negative effect.     

Adiabatic shear failure of a syntactic polymeric foam

The recent tragedy of the Columbia shuttle has drawn much attention to the potential damage that may result from high velocity impact of foam on structural components. For obvious reasons, the emphasis was put on the structure rather than on the foam itself. We performed impact tests of polyurethane foam cylinders on various metallic plates, using small lightweight (m≈1.4 gr) cylinders launched at velocities in the range of 235–280 m/s. In addition to the resulting structural damage, we observed a peculiar and previously unreported failure mode for this kind of foam, which bears a high similarity to adiabatic shear failure. In this paper, we describe and discuss the essential results of the study with emphasis on the new failure mechanism for dynamically loaded polymeric foam.     

基于碰撞安全性的泡沫铝填充矿用救生舱优化及性能分析

为提高矿用救生舱的碰撞安全性,设计一种泡沫铝填充矿用救生舱。利用ANSYS Workbench的参数优化模块,以舱体的加速度、变形及吸能大小为优化目标,对舱体的结构参数和泡沫铝的材料性能参数进行优化。对优化后的泡沫铝救生舱的碰撞安全性进行分析,结果表明泡沫铝救生舱在质量和最大等效应力均有所降低的前提下,泡沫铝救生舱碰撞时的最大变形和最大加速度得到显著降低并且舱体吸收的能量得到大幅提升,证明泡沫铝填充救生舱具有更佳的碰撞性能可以提高其安全性。     

Compression fatigue performance of a fire resistant syntactic foam

Compression–compression fatigue test study of a fire resistant Eco-Core was conducted at two values of stress ratios (R = 10 and 5). Tests were conducted at S_min/S_o values of 0.9–0.6 for R = 10 and 0.95–0.8 for R = 5. Here S_min is the maximum compression stress and S_o is the compression strength. The study showed that Eco-Core has well defined failure modes and associated fatigue lives. The failure modes are: damage on-set; damage progression, and final failure. The damage on-set, propagation and final failure were characterized by 2%, 5% and 7% changes in compliance. The three failure modes were found to be same for both static and fatigue loadings. The endurance limit was found to be 0.72S_o, 0.75S_o and 0.76S_o, respectively for three failure modes for R = 10 and 0.81S_o, 0.82S_o and 0.82S_o, respectively for R = 5. The fatigue life is defined by a power law equation, S_min/S_o = A_oN^α. Constants of the equation were established for all three modes of failures and the two stress ratios. Finally, fatigue life was found to be less sensitive to R ratio when expressed in terms of stress range versus number of load cycles, which is similar to that of metallic materials.     

Studies on compressive failure features in syntactic foam material

Syntactic foam made by mechanical mixing of glass hollow spheres in epoxy resin matrix is characterized for compressive properties in the present study. Volume fraction of hollow spheres in the syntactic foam under investigation is kept at 67.8%. Effect of specimen aspect ratio on failure behavior and stress-strain curve of the material is highlighted. Considerable differences are noted in the macroscopic fracture features of the specimen and the stress-strain curve with the variation in specimen aspect ratio, although compressive yield strength values were within a narrow range. Post compression test scanning electron microscopic observations coupled with the macroscopic observations taken during the test helped in explaining the deviation in specimen behavior and in gathering support for the proposed arguments.     

泡沫铝填充薄壁金属管塑性变形缓冲器吸能特性的试验研究

摘要：通过试验方法研究了泡沫铝填充薄壁金属管塑性变形缓冲器在准静态作用下的吸能特性。首先,进行了泡沫铝,薄壁金属管塑性变形缓冲器及泡沫铝填充薄壁金属管塑性变形缓冲器的轴向压缩试验。然后,根据试验结果,对泡沫铝填充薄壁金属管塑性变形缓冲器的吸能特性进行了分析,并与独立的泡沫铝及薄壁金属管塑性变形缓冲器的吸能特性进行了比较。结果表明,泡沫铝填充薄壁金属管塑性变形缓冲器的吸能特性有了很大的提高。在吸收的能量一定时,泡沫铝填充结构能够减少吸能结构所需要的体积与质量。     

泡沫铝填充装甲抗射流侵彻的防护性能研究

为提高装甲抗聚能射流侵彻性能,研究新型的泡沫铝填充装甲,运用ANSYS/LS-DYNA 3D有限元分析软件,对聚能射流侵彻泡沫铝填充装甲过程进行数值模拟,对比分析均质装甲和泡沫铝填充装甲的防护性能,结果表明:泡沫铝填充装甲较均质装甲有更好的防护性能。通过运用正交分析法研究前置靶板厚度、靶板材料、泡沫铝厚度、泡沫铝密度对装甲防护性能的影响,得到最优方案。研究结果对泡沫金属填充装甲的工程应用有一定的参考价值。     

Compression fatigue performance of a fire resistant syntactic foam

Compression–compression fatigue test study of a fire resistant Eco-Core was conducted at two values of stress ratios (R = 10 and 5). Tests were conducted at S_min/S_o values of 0.9–0.6 for R = 10 and 0.95–0.8 for R = 5. Here S_min is the maximum compression stress and S_o is the compression strength. The study showed that Eco-Core has well defined failure modes and associated fatigue lives. The failure modes are: damage on-set; damage progression, and final failure. The damage on-set, propagation and final failure were characterized by 2%, 5% and 7% changes in compliance. The three failure modes were found to be same for both static and fatigue loadings. The endurance limit was found to be 0.72S_o, 0.75S_o and 0.76S_o, respectively for three failure modes for R = 10 and 0.81S_o, 0.82S_o and 0.82S_o, respectively for R = 5. The fatigue life is defined by a power law equation, S_min/S_o = A_oN^α. Constants of the equation were established for all three modes of failures and the two stress ratios. Finally, fatigue life was found to be less sensitive to R ratio when expressed in terms of stress range versus number of load cycles, which is similar to that of metallic materials.     

Comprehensive analyses of syntactic foam behaviour in deepwater environment

Over the past 10 years, numerous studies were performed to better understand the behaviour of the glass syntactic foams used as thermal insulation of pipes for deepwater production. The obtained results outlined some specific behaviour of polymeric syntactic foams reinforced by glass microballoons in service conditions: both water uptake and mechanical stress have a key impact on thermal properties. This article focuses first on the wet behaviour of glass syntactic foams. The effect of water is investigated to better model the nature of water diffusing in syntactic foams with and without a topcoat protection. Secondly, the effect of hydrostatic pressure on coated structure is addressed by using a confined compression test. As polymer material is bonded to the steel surface, it is not submitted to pure hydrostatic loading but to non-spherical loading in the vicinity of the pipe. The confined compression test is then chosen to represent these non-spherical loadings of material. The rupture of glass microballoons is monitored by acoustic emission for different matrices and attempts are made to quantify the resulting acoustic emission signals by comparison with prior tomography results. These experimental analyses provide a better understanding of the main factors affecting the functional properties of syntactic foams.     

Thermal conductivity of liquid hydrogen filled foam

The effective thermal conductivities of silica aerogel foam [0.1(10)⁻³ kg m⁻³ nominal density] filled with liquid n-H₂, liquid n-D₂ and an equimolar mixture of liquid H₂D₂ were measured near 19.6 K. Our measured value of 97 mW m⁻¹ K⁻¹ for hydrogen filled foam is essentially the same as for the liquid alone. This result agrees with predictions for the thermal conductivity of porous systems which give a 2% enhancement in the effective thermal conductivity for this system relative to the liquid alone.     

Stabilizing intermetallic phases within aluminum foam

Because of ambiguity in microstructural characterization of cell wall material of Alporas® aluminum foam in literature until now, the study was focused to contribute to the examination of microstructural variability, and to reveal differences in distribution of stabilizing intermetallic phases in microstructure and their identification. It was shown that the microstructure consists of four precipitates distributed in α-Al matrix. The energy-dispersive X-ray spectroscopy revealed the presence of precipitates with compositions of AlCa, AlCaTi, AlCaFe and AlCaTiFe. However, selected area electron diffraction and X-ray diffraction confirmed that all analyzed precipitates could be indexed only in terms of tetragonal Al₄Ca or cubic Al₂₀CaTi₂. It was shown that the distribution of intermetallic compounds in cell wall material is affected by height position in the foamed block — they are either distributed along the grain boundaries of α-Al in the bottom area or they are dispersed in the α-Al matrix in the middle and top area.     

Lightweight mortar made with recycled polyurethane foam

This paper presents results of an experimental study on the use of rigid polyurethane foam wastes with cement-based mixtures to produce lightweight mortar. Several mortar grades were obtained by mixing cement with different amounts of polyurethane, aggregate and water. Dosages were varied to replace aggregates with recycled polyurethane, while the amount of water was optimized to obtain good workability. Rigid polyurethane was ground to particle sizes of less than 4 mm prior to use as an aggregate substitute. The characteristics of the test specimens were defined and they were tested in both a fresh and a hardened state. Results show that an increase in the amount of polyurethane affects the mortar, decreasing its density and mechanical properties while increasing its workability, permeability, and occluded air content. These results confirm that mortar produced with recycled polyurethane is comparable to lightweight mortar made with traditional materials.