泡沫铝填充管的研究进展

泡沫铝填充管是在一个或多个不同横截面形状的薄壁金属管内填充泡沫铝而形成的一种结构功能一体化材料。泡沫铝的填充不仅提高了薄壁金属管的轴向压缩性能和抗弯曲性能,也避免了泡沫铝本身强度不高的劣势。从泡沫铝填充管的制备、结构及性能方面综述了其研究现状,从泡沫铝单管、双管与多管填充的角度分析了结构对泡沫铝填充管压缩和弯曲性能的影响。单管填充泡沫铝改变了薄壁管压缩及弯曲的失效形式,提高了薄壁管的吸能性;双管填充泡沫铝的内管多数以同心管形式排列,在管内部所填充的泡沫铝支撑的基础上,内管进一步支撑起泡沫铝填充管的承载和吸能作用,其压缩及弯曲性能较单管填充更为突出;多管填充泡沫铝在双管基础上进行拓展,可以同心或并列排布,对薄壁管性能的提升各有不同,平行排列的多管结构能量吸收效率高于泡沫铝填充单管,但低于相应的薄壁空管结构。泡沫铝填充管的制备技术通常是分别制取泡沫铝和管材再进行填充,尽管过于单一且工艺复杂,但由于其具有优异的承载和吸能能力,仍然在交通运输、航空航天等领域极具应用潜力。     

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.     

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.     

Experimental and numerical analyses of bending of foam-filled sections

Summary Numerical simulations and experiments are conducted to study the bending crush behavior of thin-walled columns filled with closed-cell aluminum foam. A nonlinear dynamic finite element code was used to simulate quasi-static three point bending experiments. The aluminum foam filler provides a higher bending resistance by retarding inward fold formation at the compression flange Moreover, the presence of the foam filler changes the crushing mode from a single stationary fold to a multiple propagating fold. The progressive crush prevents the drop in load carrying capacity due to sectional collapse. Henceforth, the aluminum foam filling is very attractive to avoid global failure for a component which undergoes combined bending and axial crushing. This phenomenon is captured from both experiment and numerical simulation. It was found that partially foam-filled beams also still offer, high bending resistance, and the concept of the effective foam length is developed. Potential applications of foam-filled sections for crashworthy structures are suggested.     

复合泡沫填充管的高g值冲击防护特性

目的 为避免或减小高g值冲击对弹内轻质元器件的破坏,应加强对轻质元器件缓冲防护结构的研究。方法 基于新型复合泡沫和通孔泡沫铝的2种泡沫填充管,通过万能试验机和落锤冲击系统研究了2种泡沫填充管的静动态力学特性,并运用数值模拟方法研究高g值冲击下等质量的泡沫填充管与夹芯管的加速度缓冲效果和吸能机制。结果 数值模拟所得结构变形和落锤加速度与实验结果较为一致,验证了数值模拟方法的可靠性。复合泡沫平台应力具有显著的应变率效应,其填充管压溃载荷平稳且高于泡沫铝填充管,比泡沫铝填充管体现出更优异的高过载防护性能。等质量的泡沫夹芯管的抗冲击性能优于填充管,2种泡沫填充而成的夹芯管具有相似的高过载防护性能,泡沫材料压缩行为对夹芯管压溃载荷特征的影响低于填充管。结论 所得结果对轻质元器件的高g值缓冲防护有较强的指导意义。     

Crashworthiness assessment of auxetic foam-filled tube under quasi-static axial loading

This present study investigates experimentally and numerically the crush response and energy absorption performances of auxetic foam-filled square tubes under quasi-static axial loading. Three different structures: empty, conventional and auxetic foam-filled square tubes have been compared and examined with respect to the deformation modes and load–displacement curves. Standard compression tests were conducted on the tubes to evaluate the influence of auxetic foam in the energy absorption of empty tubes. Moreover, results from computer simulation have also been supplemented to further examine the abovementioned effect. It is discovered that the auxetic foam-filled square tube is superior to empty and conventional foam-filled square tubes in terms of all studied crashworthiness indicators.     

Optimization of foam-filled bitubal structures for crashworthiness criteria

Thin-walled structures have been widely used as key components in automobile and aerospace industry to improve the crashworthiness and safety of vehicles while maintaining overall light-weight. This paper aims to explore the design issue of thin-walled bitubal column structures filled with aluminum foam. As a relatively new filler material, aluminum foam can increase crashworthiness without sacrificing too much weight. To optimize crashworthiness of the foam-filled bitubal square column, the Kriging meta-modeling technique is adopted herein to formulate the objective and constraint functions. The genetic algorithm (GA) and Non-dominated Sorting Genetic Algorithm II (NSGA II) are used to seek the optimal solutions to the single and multiobjective optimization problems, respectively. To compare with other thin-walled configurations, the design optimization is also conducted for empty bitubal column and foam-filled monotubal column. The results demonstrate that the foam-filled bitubal configuration has more room to enhance the crashworthiness and can be an efficient energy absorber.     

填充泡沫铝的多层铝管动态压溃吸能特性研究

采用数值模拟的方法研究和分析了无填充物的多层铝管结构的吸能特性,结果发现多层铝管相比单层铝管,不但具有较大的吸能量,而且还具有较高的比吸能率;在此基础上,设计了不同层数的多层管泡沫铝填充结构,研究发现泡沫铝不但受轴向压溃变形,同时也受到了铝管层之间的相互作用力使其在径向发生了变形;之后对多层管填充3种不同密度的泡沫铝,采用变参分析的方法研究了多层管层数和泡沫铝密度对整个结构吸能特性的影响;研究结果表明:填充泡沫铝的多层管,随着层数的增加,其比吸能率和吸能量也随之有所增加,随着泡沫铝密度的提高,比吸能率的提高量开始下降,但仍高于填充相同泡沫铝的单层管。     

Experimental investigation of interaction effects in foam-filled thin-walled aluminum tubes

The interaction coefficients of polystyrene foam filling of thin-walled aluminum cylindrical tubes were investigated experimentally through compression testing of partially foam-filled tubes with and without adhesive. The experimental load-displacement curves and observation of the crushed sections of filled tubes have shown that partial foam filling reduced the fold length and hence increased the average crushing loads of tubes, proving the interaction effect between tube wall and filler. The interaction coefficients for the partial foam filling were further calculated to be in the level and/or higher than that of the foam plateau load of transverse direction.     

Bending behavior of empty and foam-filled beams: Structural optimization

Bending crash tests on empty and foam-filled square aluminum beams have been performed. Furthermore, in order to find more details about crash processes, finite element simulations have been done. In terms of improving crash behavior of the aluminum beams, the crashworthiness optimization procedure has been applied to maximize specific energy absorption of the square beams with the target energy absorption. A comprehensive study about the strengthening effect of foam in the filled beam has been performed and finally the optimization technique has been implemented to find the optimum foam-filled beam that absorbs the same energy as optimum empty tubes with lower weight.     

Crushing response of foam-filled conical tubes under quasi-static axial loading

Foam-filled thin-walled tubes are considered to be desirable energy absorbers under axial loading due to their higher energy absorption compared with empty tubes. This paper treats the axial crushing and energy absorption response of foam-filled conical tubes under quasi-static axial loading, using non-linear finite element models. Influence of important parameters such as wall thickness, semi-apical angle and density of foam filler was investigated and the results highlight the advantages of using foam-filled conical tubes as energy absorber. Results also indicate that the crush and energy absorption performances of conical tubes are significantly enhanced by foam filling. The primary outcome of the study is new research information and development of empirical relations which will facilitate the design of foam-filled conical tubes as energy absorbers in impact applications.     

Modeling of material failure in foam-based components

The modeling of material failure in foam-filled beams was explored through numerical analyses with LS-DYNA. The study was based on previous physical tests on bending of square aluminum extrusions filled with aluminum foam. Recently implemented material models including fracture criteria for both extrusion and foam were used in the analyses. The objectives were to verify the numerical model, and to investigate the influence of different fracture criteria on the response.     

泡沫铝填充薄壁铝合金多胞构件与单胞构件吸能性能研究

为研究泡沫铝填充薄壁铝合金多胞结构与单胞结构的吸能能力,该文基于有限元软件LS-DYNA建立了泡沫铝填充薄壁铝合金多胞结构与单胞结构的数值仿真。对经典薄壁圆管试验及泡沫铝填充薄壁圆管试验进行了数值模拟,分析表明该数值模型能够较好的模拟泡沫铝填充薄壁圆管在轴向冲击过程中的撞击力和变形发展。基于该模型对比研究了不同因素下泡沫铝填充薄壁铝合金多胞结构与单胞结构的轴向吸能特性,分析了其破坏模式、吸能机理和两者吸能效率。结果表明:在轴向冲击荷载作用下,泡沫铝填充薄壁铝合金的破坏模式为轴对称渐进折叠破坏模式,冲击力-位移曲线和变形模态图显示其变形过程分为3个阶段:弹性阶段、平台阶段和强化阶段。当冲击压缩距离为构件高度的80%时,7种不同参数下的泡沫铝填充薄壁铝合金多胞结构的吸能效率明显高于7种单胞结构,吸收的能量E和比吸能SEA都提高了50%以上,是一种优秀的吸能构件,可广泛应用于防护工程中。     

Dynamic energy absorption characteristics of foam-filled conical tubes under oblique impact loading

This paper treats the crush behaviour and energy absorption response of foam-filled conical tubes subjected to oblique impact loading. Dynamic computer simulation techniques validated by experimental testing are used to carry out a parametric study of such devices. The study aims at quantifying the energy absorption of empty and foam-filled conical tubes under oblique impact loading, for variations in the load angle and geometry parameters of the tube. It is evident that foam-filled conical tubes are preferable as impact energy absorbers due to their ability to withstand oblique impact loads as effectively as axial impact loads. Furthermore, it is found that the energy absorption capacity of filled tubes is better maintained compared to that of empty tubes as the load orientation increases. The primary outcome of this study is design information for the use of foam-filled conical tubes as energy absorbers where oblique impact loading is expected.     

Investigating the quasi-static axial crushing behavior of polymeric foam-filled composite pultrusion square tubes

The capability of structures to absorb large amounts of energy is a crucial factor, particularly for structural components of vehicles, in reducing injury in case of collision. In this study, an experimental investigation was conducted to study the crashworthiness of polymeric foam-filled structures to the pultruded square cross-section E-Glass fiber-reinforced polyester composite tube profiles. Quasi-static compression was applied axially to composite tubes to determine the response of the quasi-static load displacement curve during progressive damage. Three pultruded composite tube wall thicknesses at different sizes were examined, and the effects of crushing behavior and failure modes were analyzed and discussed. Experimental results indicated that the foam-filled profile is superior to the non-filled foam composite tube profile in terms of the capacity to absorb specific energy.     

Effect of triggering and polyurethane foam-filler on axial crushing of natural flax/epoxy composite tubes

In this study, empty and polyurethane-foam filled flax fabric reinforced epoxy composite tubes were longitudinally crushed under quasi-static compression. The effects of foam-filler (density of 160 kg/m³, two diameters of 64 and 86 mm), tube thickness (2, 4 and 6 plies of laminate), and triggering (45° edge chamfering) and the combination of triggering and foam-filler on the crushing characteristics and energy absorption capacity of these tubes were investigated. The test results indicate that the observed primary failure mode was progressive crushing for all the specimens. Foam-filled tubes have better crashworthiness than empty tubes in total absorbed energy, specific absorbed energy and crush force efficiency. The presence of triggering has no significant effect on total absorbed energy and specific absorbed energy of the empty tubes. However, the crush force efficiency of triggered tube is significantly larger compared to the non-triggered one. In addition, the triggering minimises the force variation of the tubes from the average crush force and in turn a more stable progressive crushing is achieved. The foam-filled and triggered tubes have better crashworthiness than the empty tubes in all the aspects. Compared with either triggered or foam-filled tubes, the triggered and foam-filled tubes have larger values in average crush load and crush force efficiency. In terms of total absorbed energy and specific absorbed energy, the triggered and foam-filled tubes have values always larger than those of the tubes with triggering only, but these values are either larger or smaller than the tubes with foam-filler only.     

泡沫填充多边形单锥管与双锥管斜向加载下耐撞性分析

锥形泡沫填充结构结合了泡沫填充结构与锥形结构的优势,具有优异的吸能性和抵抗失稳变形的能力。研究了具有不同横截面的泡沫填充多边形单锥管(FSPTTs)与泡沫填充多边形双锥管(FBPTTs)在四种冲击角度下的耐撞性。采用多准则评估方法(COPRAS)对不同横截面的泡沫填充单锥管与泡沫填充双锥管的综合耐撞性进行了评估。评估表明:综合考虑多种冲击角度时,圆形截面泡沫填充单锥管较其他截面泡沫填充单锥管具有更好的耐撞性;圆形截面泡沫填充双锥管较其他截面泡沫填充双锥管具有更好的耐撞性。最后,针对圆形截面泡沫填充单锥管与圆形截面泡沫填充双锥管,以最大比吸能和最小峰值力为目标,采用非支配遗传算法对这两种结构在四种冲击角度下进行了多目标优化。结果表明:当冲击角度从0°变化到10°时,两种结构的Pareto曲线变化不大,而当冲击角度从10°变化到30°时,冲击角度对Pareto曲线形状和位置有显著影响;在冲击角度为0°和10°时,圆形截面泡沫填充双锥管的耐撞性优于圆形截面泡沫填充单锥管,而在冲击角度为20°和30°时,圆形截面泡沫填充单锥管的耐撞性优于圆形截面泡沫填充双锥管。实际应用中,可以根据工程需要选择合适的结构。     

Prediction of the mean folding force during the axial compression in foam-filled grooved tubes by theoretical analysis

In this article, some theoretical relations are derived to predict the mean folding force, total absorbed energy per unit of tube length and specific absorbed energy per unit of total mass by the polyurethane foam-filled grooved tubes with circular cross section under the axial compression process. During the folding process, a new theoretical model of deformation is introduced for the polyurethane foam-filler. The theoretical analysis is developed on the basis of the energy method. Some foam-filled grooved specimens were prepared and axially compressed to obtain the experimental diagram of the folding force versus the axial displacement. Comparison of the theoretical predictions with the experimental results showed a good agreement. Then, by considering the interaction effect between the polyurethane foam and the inner wall of grooved tubes, a semi-empirical relation was derived. Predictions along with considering the interaction factor obtained from the semi-empirical relation indicate a better correlation with those of the experiments.     

泡沫铝填充碳纤维增强树脂复合材料薄壁管的压缩变形行为与吸能特性

将填加造孔剂法制备的泡沫铝物理嵌入碳纤维增强树脂(Carbon fiber reinforced plastic,CFRP)复合材料薄壁管中,从而获得泡沫铝填充CFRP复合材料薄壁管的复合结构。针对CFRP薄壁管、泡沫铝和泡沫铝填充CFRP复合材料薄壁管分别开展准静态压缩试验测试其压缩和吸能性能,并在压缩过程中采用数字图像相关技术(Digital image correlation,DIC)同步分析其变形模式;进一步研究在不同环境温度下(25~150℃)泡沫铝填充CFRP复合材料薄壁管的压缩与吸能性能及失效模式。结果表明:泡沫铝作为填充芯材改变了CFRP复合材料薄壁管的压缩变形行为,由单一CFRP复合材料薄壁管的散射开花失效转变为泡沫铝填充CFRP复合材料薄壁管的纤维层断裂失效。同CFRP复合材料薄壁管相比,泡沫铝填充CFRP复合材料薄壁管的应力波动显著减小。随环境温度的升高,CFRP复合材料薄壁管、泡沫铝和泡沫铝填充CFRP复合材料薄壁管的压缩与吸能性能均不断降低,但泡沫铝与CFRP复合材料薄壁管之间的交互作用增强,泡沫铝对CFRP复合材料薄壁管的增强作用在高温下表现更为显著。      

Quasi-static and dynamic crushing of empty and foam-filled tubes

Metallic foam-filled tubes and their empty counterparts have been tested at quasi-static and dynamic strain rates in order to determine their energy absorption capabilities. Data from the Split-Hopkinson Pressure Bar have been used to generate force vs. displacement curves that are somewhat analogous to pseudo-engineering stress-strain curves. Force balance calculations have also been made. These results indicate that, on an equal weight basis, foam-filled tubes offer greater energy absorption capability than empty tubes at quasi-static strain rates. However, the benefit of foam filling does not appear to be extended to strain rates of the order of 200–500 s^–1. Force balance calculations are shown to have potential as a method for monitoring the crushing of metallic foams at high strain rate.