Predicting the Crushing Behavior of Axially Loaded Elliptical Composite Tubes Using Artificial Neural Networks

In this research work, the artificial neural networks (ANN) technique is used in predicting the crushing behavior and energy absorption characteristics of axially-loaded glass fiber/epoxy composite elliptical tubes. Predictions are compared to actual experimental results obtained from the literature and are shown to be in good agreement. Effects of parameters such as network architecture, number of hidden layers and number of neurons per hidden layer are also considered. The study shows that ANN techniques can effectively be used to predict the crushing response and the energy absorption characteristics of elliptical composite tubes with various ellipticity ratios subjected to axial loading.     

铺层顺序对复合材料薄壁圆管轴向压溃吸能特性的影响研究

采用仿真和试验相结合的方法探讨复合材料薄壁圆管在准静态轴向压缩载荷下的失效吸能特性和吸能机理。首先,建立复合材料薄壁圆管"层合壳"有限元模型,通过显式动力学方法求解其在准静态轴向载荷下的压溃失效力学行为。仿真与试验结果在圆管轴向压溃变形过程、初始峰值载荷、平均压溃载荷及比吸能等主要吸能参数上具有很好的一致性,验证了"层合壳"复合材料圆管有限元模型和建模方法的有效性。其次,采用解析模型与仿真分析方法分别对[0/90]_3s、[0/90/0₂/90₂]_s、[0₃/90₃]_s三种不同铺层顺序的复合材料圆管的屈曲载荷与吸能特性进行了对比,进一步分析了铺层顺序对圆管失效吸能特性的影响。研究表明,0°与90°铺层交替程度对复合材料圆管的吸能特性影响较大,保证纤维失效方式在结构宏观失效中占主导地位能够提高材料失效吸收能量。     

The Effects of Triggering Mechanisms on the Energy Absorption Capability of Circular Jute/Epoxy Composite Tubes under Quasi-Static Axial Loading

The usage of composite materials have been improving over the years due to its superior mechanical properties such as high tensile strength, high energy absorption capability, and corrosion resistance. In this present study, the energy absorption capability of circular jute/epoxy composite tubes were tested and evaluated. To induce the progressive crushing of the composite tubes, four different types of triggering mechanisms were used which were the non-trigger, single chamfered trigger, double chamfered trigger and tulip trigger. Quasi-static axial loading test was carried out to understand the deformation patterns and the load-displacement characteristics for each composite tube. Besides that, the influence of energy absorption, crush force efficiency, peak load, mean load and load-displacement history were examined and discussed. The primary results displayed a significant influence on the energy absorption capability provided that stable progressive crushing occurred mostly in the triggered tubes compared to the non-triggered tubes. Overall, the tulip trigger configuration attributed the highest energy absorption.     

Comparison of the crushing performance of hollow and foam-filled small-scale composite tubes with different geometrical shapes for use in sacrificial cladding structures

This paper presents the quasi-static crushing performance of nine different geometrical shapes of small-scale glass/polyester composite tubes filled with polyurethane closed-cell foam for use in sacrificial cladding structures. The effect of polyurethane foam on the crushing characteristics and the corresponding energy absorption is addressed for each geometrical shape of the composite tube. Composite tubes with two different thicknesses (1 mm and 2 mm) have been considered to study the influence of polyurethane foam on the crushing performance. From the present study, it was found that the presence of polyurethane foam inside the composite tubes suppressed the circumferential delamination process and fibre fracturing; consequently, it reduced the specific energy absorption of composite tubes. Furthermore, the polyurethane foam attributed to a higher peak crush load for each composite tube. However, the presence of polyurethane foam inside the composite tubes significantly increased the stability of the crushing phenomena especially for the square and hexagonal cross-sectional composite tubes with 1 mm wall thickness. The results from this study are compared with our previous results for composite tubes without polyurethane foam [1].     

Prediction of energy absorption in composite stiffeners

The energy absorption behavior of composite stiffeners subjected to axial compression has been investigated. Flat plate, angle, and channel specimens were fabricated of T650-35/F584 graphite/epoxy plain-weave fabric and were crush tested under axial compression. A nonlinear finite element approach was used to model the sustained crushing of the flat plate specimens, and a progressive failure model was implemented as part of the finite element analysis to enable investigation of the fundamental mechanisms involved in the crushing behavior. The progressive failure model was based on linear elastic fracture mechanics for prediction of crack growth and a set of failure criteria for predicting fiber/matrix failures that occurred as a result of large deformations. Friction between the specimen and the crushing surface was included in the model. A semi-empirical analysis methodology was developed for prediction of the energy absorption capability of composite stiffeners based on crush tests of flat plate specimens and an understanding of the fundamentals of the energy absorption process.     

Numerical Study on Hybrid Tubes Subjected to Static and Dynamic Loading

The commercial finite element program LS-DYNA was employed to evaluate the response and energy absorbing capacity of cylindrical metal tubes that are externally wrapped with composite. The numerical simulation elucidated the crushing behaviors of these tubes under both quasi-static compression and axial dynamic impact loading. The effects of composite wall thickness, loading conditions and fiber ply orientation were examined. The stress–strain curves under different strain rates were used to determine the dynamic impact of strain rate effects on the metal. The results were compared with those of a simplified analytical model and the mean crushing force thus predicted agreed closely with the numerical simulations. The numerical results demonstrate that a wrapped composite can be utilized effectively to enhance the crushing characteristics and energy absorbing capacity of the tubes. Increasing the thickness of the composite increases the mean force and the specific energy absorption under both static and dynamic crushing. The ply pattern affects the energy absorption capacity and the failure mode of the metal tube and the composite material property is also significant in determining energy absorption efficiency.     

玻璃/环氧圆柱管能量吸收细观机理

研究了玻璃纤维增强环氧圆柱管轴向撞击和准静态压缩下的能量吸收特性。总结了稳态压缩的三种宏观破坏模式,即层束弯曲、局部屈曲和横向剪切。从细观角度出发,详细研究了不同宏观破坏模式的复合材料圆柱管的能量耗散机理,并比较了吸能能力。随着铺设角度增大,能量吸收机理由基体控制向纤维与基体共同控制转化,因此能量吸收逐渐增大。本文还比较了撞击和准静态下能量吸收的特点。     

Experimental and analytical assessment of axial crushing of circular hybrid tubes under quasi-static load

In the present article, axial crushing behavior of circular aluminum/glass–epoxy hybrid tubes is studied experimentally and analytically. 48 quasi-static axial crushing experiments are carried out on bare metal and hybrid tubes to evaluate the effect of different parameters such as metal and composite wall thicknesses and stacking sequence of composite layers on the crashworthiness characteristics. The specimens are made in two types of layups including angle ply pattern [±θ]_s and multi angle ply pattern (different ply angles). The experimental results reveal that stacking sequence has a considerable effect on crashworthiness characteristics, for example for layup [90/0/0/90], the absorbed energy is more than three times of aluminum tube with the same aluminum wall thickness. Also the aforementioned layup has better energy absorption compared to [90/90/90/90] which has been previously proposed as the best layup.     

Composite sandwich structures with nested inserts for energy absorption application

Polymer composite sandwich structures are promising candidate structures for reducing vehicle mass, thereby improving the fuel economics. Nonetheless, to fully explore this material as the primary structure and energy absorber in vehicles, it is important to understand the energy absorption capability of this material. Hence, in the present work, comprehensive experimental investigation on the response of composite sandwich structures to quasi-static compression has been carried out. The crashworthiness parameters, namely the peak force, absorbed crash energy, specific absorbed energy, average crushing force and crush force efficiency of various types of composite sandwich structures were investigated in a series of edgewise axial compression tests. The tested composite sandwich specimens were fabricated from glass and carbon fiber with epoxy resin. Four distinct modes of failure were observed and recorded. The primary mode of failure observed was progressive crushing with high energy absorption capability. The optimized design in this study had a specific energy absorption capability of 47.1 kJ/kg with a good crush force efficiency of 0.77, higher than conventional metals.     

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.     

变刚度碳纤维/环氧树脂复合材料薄壁圆管轴向压溃响应与破坏机制

通过控制缠绕线型改变轴管纤维角度,制备了一种轴向刚度渐变、压溃稳定的碳纤维增强树脂基复合材料(CFRP)变刚度薄壁圆管。对变刚度、[±45°]_n以及[90°]_n三类CFRP缠绕轴管进行轴向准静态压缩测试,结合数字图像相关技术(DIC)及有限元结果,对比三类结构压溃初始应变模式、损伤演化与应力状态结果,研究了变刚度结构的压溃响应与破坏机制。结果表明:不同纤维角度CFRP轴管因轴向刚度不同,压溃的初始破坏与损伤演化过程相异,三类结构产生不同的压溃响应与破坏模式。变刚度区连续变化的大角度纤维能有效地引发分层和"开花式"混合破坏,缓慢释放应变能,使变刚度CFRP轴管吸能效果明显优于其他两类结构。其峰值载荷为66.97 kN,压溃效率为50.8%,比吸能为10.1 kJ/kg,相对于[±45°]_n结构比吸能提升156.35%,压溃效率提升518.76%,相对于[90°])n结构比吸能提升16.9%,压溃效率降低27.3%。     

Effect of fiber orientation on energy absorption characteristics of glass cloth/epoxy composite tubes under axial quasi-static and impact crushing condition

The collapse characteristics and energy absorption capability of composite tubes made of 759/5224 woven glass cloth/epoxy with different fiber orientations were studied in the present article under axial quasi-static and impact crushing condition. The effects of fiber orientation and loading condition on the crushing modes and energy absorption capability were discussed in detail. The fiber orientation could be found to have significant influences on energy absorption performance. Based on results, the energy absorption capability could be improved by selecting proper fiber orientation. The energy absorption capability in impact crushing tests could be found to be slightly lower than that in quasi-static crushing tests.     

Crushing response of composite corrugated tubes to quasi-static axial loading

This paper is devoted to examine the crushing behaviour of axially crushed composite corrugated tubes. Two types of composites were tested, namely, carbon fibre/epoxy in a filament form and glass fibre/epoxy in woven roving form. A series of experiments was conducted for tubes with corrugation angle (β) ranging from 10° to 40°. Typical failure histories of their failure mechanisms are presented and discussed. The results showed that the crushing behaviour of composite corrugated tube is found to be sensitive to the change in corrugation angle and fibre type. Carbon/epoxy tubes with corrugation angle of 40° displayed the highest specific energy absorption capability. It is also found that introducing of corrugation could significantly enhance the energy absorption capability of composite tubes in a uniform manner.     

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.     

Ellipticity Ratio Effects in the Energy Absorption of Axially Crushed Composite Tubes

In this paper, the influence of ellipticity ratio on energy absorption capability and load-carrying capacity of woven roving wrapped composite elliptical tubes has been investigated both experimentally and numerically. A series of experiments was conducted for composite elliptical tubes with ellipticity ratios (a/b) ranging from 1 to 2. Typical failure histories of their failure mechanism are presented and discussed. The experimental data are correlated with predictions from a finite element model. Load-deformation curves and deformation histories of typical specimens are presented and discussed. For all specimens considered, classical axial collapse eigenvalues were computed. The results showed that the ellipticity ratio significantly influenced the energy absorption capabilities as well as the load-carrying capacity. Tubes with ellipticity ratios of a/b 1.25 and 2.0 displayed the highest normalised specific energy absorption capability. A reasonable agreement between the experimental and computational results was obtained for the critical crush load.     

Predicting the Fatigue Life of Different Composite Materials Using Artificial Neural Networks

Artificial Neural Networks (ANN) have been recently used in modeling the mechanical behavior of fiber-reinforced composite materials including fatigue behavior. The use of ANN in predicting fatigue failure in composites would be of great value if one could predict the failure of materials other than those used for training the network. This would allow developers of new materials to estimate in advance the fatigue properties of their material. In this work, experimental fatigue data obtained for certain fiber-reinforced composite materials is used to predict the cyclic behavior of a composite made of a different material. The effect of the neural network architecture and the training function used were also investigated. In general, ANN provided accurate fatigue life prediction for materials not used in training the network when compared to experimentally measured results.     

Crushing and energy absorption performance of different geometrical shapes of small-scale glass/polyester composite tubes under quasi-static loading conditions

This paper presents the quasi-static crushing performance of nine different geometrical shapes of small-scale composite tubes. The idea is to understand the effect of geometry, dimension and triggering mechanism on the progressive deformation of small-scale composite tubes. Different geometrical shapes of the composite tubes have been manufactured by hand lay-up technique using uni-directional E-glass fabric (with single and double plies) and polyester resin. Dedicated quasi-static tests (144 tests) have been conducted for all nine geometrical shapes with different t/D (thickness–diameter) ratios and two triggering profiles (45° chamfering and tulip pattern with an included angle of 90°). From this unique study, it was found that the crushing characteristics and the corresponding energy absorption of the special geometrical shapes are better than the standard geometrical shapes such as square and hexagonal cross sections. Furthermore, the tulip triggering attributed to a lower peak crush load followed by a steady mean crush load compared to the 45° chamfering triggering profile which resulted into a higher energy absorption in most of the geometrical shapes of the composite tubes.     

A study on crushing behaviors of composite circular tubes with different reinforcing fibers

In this study, the failure modes and energy absorption capabilities of different kinds of circular tubes made of carbon, Kevlar, and carbon-Kevlar hybrid fibers composites with epoxy resin have been evaluated. The relationship between the crushing parameters (specific energy absorption, maximum peak load, mean crushing load) and the material properties for different fibers and patterns was also investigated. The fabric carbon/epoxy tubes had the best energy absorption capability (specific energy absorption of 81.7%). In contrast, the tubes made of Kevlar showed the worst energy absorption capability. Based on the linear regression analysis results, the crushing parameters generally showed good correlation with the compressive strength and shear modulus. In particular, the specific energy absorption of the tubes with the brittle fracture mode revealed the strongest correlation with the compressive strength (R-square value = 0.90).     

Axial capacity and crushing behavior of metal–fiber square tubes – Steel,stainless steel and aluminum with CFRP

Composite metal-carbon fiber reinforced polymer (CFRP) tubes combine the benefits of the high strength to weight ratio of the fiber/resin composite and the stable, ductile plastic collapse mechanism of the metal, to form a composite tube with high strength and energy absorption capability. This paper investigates the axial capacity and crushing behavior of square hollow section (SHS) tubes composed of composite steel-CFRP, stainless steel-CFRP and aluminum-CFRP. Experiments of tubes with different metal SHS geometries and two different matrix layouts of carbon fibers are described, and a general theory to predict the compression buckling, axial capacity, axial collapse and mean crush load of metal–fiber square tubes is developed and validated against the experimental results. It is shown that carbon fiber may be successfully externally bonded to metal SHS, and such application may be provided to improve the performance of existing structures, or to design new structures with enhanced strength-weight and energy absorption-weight ratios. Comparisons are made between the performance of the different types of metals, SHS geometries and carbon fiber matrix layouts.     

Comparative research on the crashworthiness characteristics of woven natural silk/epoxy composite tubes

This study investigated the energy absorption response of triggered and non-triggered woven natural silk/epoxy composite rectangular tubes subjected to an axial quasi-static crushing test. The rectangular composite tubes were prepared by the hand lay-up technique using 12 layers of silk fabric with a thickness of 1.7 mm and tube lengths of 50, 80, and 120 mm. The parameters measured were peak load, energy absorption, and specific energy absorption (SEA). In both triggered and non-triggered tubes, the SEA values decreased with increasing length of the composite specimen. On the contrary, total energy absorption increased with increasing length of the composite specimen. The peak load in triggered specimens is nearly half of that in non-triggered specimens. Deformation morphology shows that the specimens failed in two distinct modes: local buckling and mid-length buckling. The non-triggered composite tubes exhibited catastrophic failure, whereas the triggered composite tubes only exhibited progressive failure.