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![Example of typical bumper beam and tubular front rail assembly [2].](profile/Paolo-Feraboli/publication/229309226/figure/fig15/AS:668419288477715@1536374985490/Example-of-typical-bumper-beam-and-tubular-front-rail-assembly-2.png)
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![Fig. 1. Example of typical bumper beam and tubular front rail assembly [2].](profile/Paolo-Feraboli/publication/229309226/figure/fig15/AS:668419288477715@1536374985490/Example-of-typical-bumper-beam-and-tubular-front-rail-assembly-2_Q320.jpg)
![Fig. 2. Comparison of specimen geometry on the measured SEA [5] in J/g...](profile/Paolo-Feraboli/publication/229309226/figure/fig14/AS:668419288477712@1536374985457/Comparison-of-specimen-geometry-on-the-measured-SEA-5-in-J-g-for-two-different_Q320.jpg)
Carbon/epoxy square tubes and channel sections have been used in modern automotive and aircraft structures, respectively, as dedicated components designed to dissipate energy under controlled collapse. However, there are currently no specialized test methods for the characterization of Specific Energy Absorption (SEA) of composite materials. A syst...
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... Furthermore, the overall response is highly dependent on a number of parameters, including the geometry of the structure, material system, lay-up, and impact velocity. Tubular structures are used by the motorsport and automotive industries as dedicated members to absorb energy in the event of a crash, including automotive-sized front rails ( Fig. 1). Prepreg or fabric can easily be formed to tubular shapes and is the material of choice for the motorsport industry. Although no standard shape or dimension exists, either circular or square tubes have been tra- ditionally employed, the latter having rounded corners ...
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... manner, Figs. 7-11b, exhibiting frond formation and bending, particularly spec- imens II-V. The square tube, specimen I, exhibits an accordion- type of crushing, comprised of a succession of local segments folding on each other. It should be observed that the predominant failure mode at the corner is tearing fracture of the woven fiber tows (Fig. 10b), while in the flat segments it is lamina bending of the fronds. The load-displacement curves recorded show a rela- tively stable sustained force forming after the initiation of the crush, particularly for the corner element (Fig. 13). Stroke efficiency for all shapes varies between 1.38 and 1.65, which are right around the ...
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... It should be observed that the predominant failure mode at the corner is tearing fracture of the woven fiber tows (Fig. 10b), while in the flat segments it is lamina bending of the fronds. The load-displacement curves recorded show a rela- tively stable sustained force forming after the initiation of the crush, particularly for the corner element (Fig. 13). Stroke efficiency for all shapes varies between 1.38 and 1.65, which are right around the traditionally recommended value of 1.5 for effi- cient crushing. The load-stroke trace for one of the corner elements is shown in Fig. 14, from which the EA and SEA curves can be cal- culated. The results are normalized to their respective ...
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... a rela- tively stable sustained force forming after the initiation of the crush, particularly for the corner element (Fig. 13). Stroke efficiency for all shapes varies between 1.38 and 1.65, which are right around the traditionally recommended value of 1.5 for effi- cient crushing. The load-stroke trace for one of the corner elements is shown in Fig. 14, from which the EA and SEA curves can be cal- culated. The results are normalized to their respective maximum values in order to be plotted in one chart. The EA curve is nearly perfectly linear, and the SEA curve shows a relatively smooth and rapid increase up to its horizontal asymptotic value (in a fashion similar to what in metals ...
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... general, it can be seen from Fig. 15 that the small corner ele- ment exhibits a much higher SEA than the other specimens, fol- lowed by the small and large C-channels, the square tube and, lastly, the large corner element. The small corner, exhibiting the least amount of flat segments in its cross-section, is therefore the most efficient in dissipating energy per unit ...
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... most efficient in dissipating energy per unit mass of material crushed, and this can be attributed to the tearing failure mecha- nism observed. On the other hand, the large corner is the least effi- cient, exhibiting the most amount of flat segments in its cross- section, and this can be attributed to the frond bending failure mechanism observed. Fig. 16 shows the variation of SEA for all five shapes (denoted SEA i , where i = I-V) normalized to the SEA of the corner element (denoted as SEA IV ) as it varies as a function of DS, which is given by Eq. ...
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... Eq. (6) is solved for the unknown value of SEA f since all other quantities are either known or can be measured experimentally, it is possible to extrapolate the in situ value of the SEA associated with flat sections, like the ones that form the fronds observed in splaying failure. The average value obtained this calculation is SEA f = 16.3 J/g (Fig. 17), which is much lower than the average SEA IV = 62 J/g recorded during the crushing of the corner elements. Although there is evident variation in the results, it is consistent with the CoV measured between repetitions. In conclusion, although the corner element exhibits a higher measured SEA than any of the other shapes tested, the ...
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... validate these observations, a limited number of tests are performed using the special fixture developed by the authors [7]. As seen in Fig. 18, the SEA measured using the flat specimen varies greatly according to the value of unsupported height used. For 0 in. (0 mm) of unsupported height, which means for a fully constrained specimen as in the case of the original NASA fixture, the SEA mea- sured greatly overestimates the real SEA of the material. As the unsupported height is ...
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... an asymptotic value of 22.9 J/g. Although slightly higher, this value is relatively close to the one determined in situ through Eq. (6). At the same time, it suggests that the flat plate test meth- odology tends to overestimate the SEA, possibly due to unknown fixture effects, such as friction. A typical flat specimen before test- ing is shown in Fig. 19, left, where the sawtooth trigger is clearly visible. A typical post-crush specimen is shown in Fig. 19, right, for an unsupported height of 0.5 in. (12.5 mm). From the study it is possible to note that the degree of curvature greatly influences the energy absorption behavior: the more con- toured the specimen cross-section, the higher ...
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... in situ through Eq. (6). At the same time, it suggests that the flat plate test meth- odology tends to overestimate the SEA, possibly due to unknown fixture effects, such as friction. A typical flat specimen before test- ing is shown in Fig. 19, left, where the sawtooth trigger is clearly visible. A typical post-crush specimen is shown in Fig. 19, right, for an unsupported height of 0.5 in. (12.5 mm). From the study it is possible to note that the degree of curvature greatly influences the energy absorption behavior: the more con- toured the specimen cross-section, the higher the energy dissi- pated per unit mass of material. This observation becomes evident in Fig. 20, which ...
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This paper proposes a systematic strategy to determine the mechanical behaviour of composite materials up to failure using numerical and experimental approaches in parallel. A multiscale virtual design/testing strategy is presented that takes into account the physical mechanisms of damage at the different length scales, so the influence of the micr...
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... Otherwise, the effects of geometry design parameters have been studied and can be found in some literature. Feraboli et al. [7] investigate the effect of geometry design parameters on the crush behaviour of the carbon fibre epoxy tubes and C-channels. The results show that the small corner has presented the most efficient design in absorbing energy. ...
During an evacuation, the tsunami lifeboat should be able to withstand the possible external loads that might be occurred, such as collisions, violent crashes, and capsizing events. Special structural reinforcement and improvement, such as a crash absorber, are attached to prevent damage due to the impact load. Therefore, this article focuses on the crushing behaviour of the tsunami lifeboat crash absorber made of the multi-cell glass fibre-reinforced composite panel. The effect of the cross-section geometry design of the cell on the damage mechanism and energy absorption behaviour was investigated. The explicit dynamic finite element method was used to identify the multi-cell configuration’s crashworthiness performance. Experimental studies such as tensile and three-point bending tests were conducted to define the material properties and validation of the FE model. The simulation results showed that the explicit dynamic finite element method has effectively estimated the crash absorber crushing damage. The circular cross-section has shown the most significant crash absorption capability compared to the others, namely the honeycomb, the square, and the triangular cell. Furthermore, the 4CSM laminate type has revealed a lower energy absorption than the 4WRC45 and 4WRC laminates. Otherwise, the study exhibits that the cross-sectional geometry and the laminate type significantly influence the crash absorber performance for improving the tsunami lifeboat crashworthiness.
... 34,35 The mechanical response of the composite channel structure subjected to quasi-static crushing has been studied, and it is found that the failure modes of the structure are mainly corner damage and buckling failure. 36,37 The buckling of CCSS under axial compression is also studied, and the buckling mode and buckling load are obtained by experiment and numerical simulation. 38 In addition, the relationship between the boundary conditions and the buckling behavior and critical load of CCSS under pure bending is also discussed in detail. ...
... The CCSS is manufactured of carbon fiber/epoxy fabric. 37 The material properties of this fabric and the damage parameters used for numerical modeling are shown in Table 1. 40,41 The crushing model is developed based on the user subroutine VUMAT in ABAQUS/ Explicit. ...
To induce the progressive crushing of composite channel section structure (CCSS), the bevel and steeple trigger are proposed and designed. A nonlinear damage model considering both damage initiation and evolution of intra-ply and inter-ply is developed. The damage initiation and stiffness degradation processes of intra-ply are predicted by the maximum stress criterion and an exponential evolution law, respectively. The adhesion behavior between adjacent plies is modeled following the surface-based cohesive contact method, and the delamination failure behaviors of inter-ply are predicted using the traction-separation model. The effects of different configurations of bevel and steeple trigger on the energy absorption characteristics of CCSSs subjected to quasi-static axial loading are compared and analyzed. The results show the initial peak load of CCSS using the bevel and steeple trigger has a negative correlation function with the bevel angle. The steeple trigger can induce progressive crushing of the structure and significantly enhance the specific energy absorption (SEA).
... In the open literature, many experimental investigations related to composite crashworthiness studies have been reported, such as different types of fibres [17][18][19] and resin [20,21], laminate design [19,22,23], trigger configurations [24], geometry [25][26][27], etc. However, most of these studies used synthetic fibre composites or natural fibre composites, leaving a huge gap in justifying the crashworthiness capability of eco-hybrid composites. ...
... Because of the fuselage subfloor application, it is normally designed with self-supporting web profiles [29]. Besides that, one of the notable advantages of this structure is its ability to self-support without the need for a dedicated test fixture [30], and it is robust to the trigger design [26]. In terms of failure modes, the self-supporting web profiles generally experienced a mixed mode failure, which includes both splaying and fragmentation that could absorb high crash energy. ...
This study investigates the quasi-static axial crushing tests of eco-hybrid composites based on flax and E-glass fibres strengthened with polyester resin. Five different configurations of self-supporting webs were fabricated to investigate the crushing behaviours of this eco-hybrid composite with different stacking sequences based on intercalation and sandwich-like sequences. The effect of different open-section web profiles was also investigated. The results were plotted in load-displacement curves and the specific energy absorption (SEA), as well as the crushing force efficiency (CFE), were calculated to evaluate the crushing response of each configuration. The test results verified the crushing mechanisms related to the energy absorption depending on the stacking sequence as well as the frontal profile. In this study, all specimens with the intercalation stacking sequence have achieved higher SEA and CFE than specimens with a sandwich-like stacking sequence. In terms of the frontal profile, the sine wave hat shape had the highest CFE, up to 80% compared to other web profiles. Thus, it demonstrated the capability of a sine wave hat-shape eco-composite based on flax fibre to be applied as a crashworthy material.
... The damage morphologies of the tested specimens showed that each side of the tube wall was again compressed into two parts. One part opened to the outside and the other part folded to the inside of the tube, forming a "frond bending failure" [48]. The broken material powder covered the crush surface, making it flat and smooth. ...
In this study, the structural regularity of staggered and overlapped aragonite tiles in nacre was used to design novel carbon/epoxy composite tubes with improved energy absorption behaviors. Dynamic drop hammer impact tests were performed on both continuous square tubes (QC) and nacre-inspired composite (QD) tubes under different impact energies. The data suggested that impact energy of 1059.63 J resulted in an average crushed length of 49.87 mm for QC tubes and 37.86 mm for QD tubes, equivalent to 24% reduction. Moreover, the specific energy absorption (SEA) of QD tubes was about 36% higher than that of QC tubes. The fractographic analyses of the QD tubes revealed that the improved energy absorption performances were attributed to the crack deflection and parallel propagation of multiple cracks during the crushing process. These findings look promising for the design and fabrication of future passive security devices with advanced properties.
... Bolukbasi and Laananen (1995) studied the energy-absorbing performance of composite flat plates, angle, and channel sections under axial compression and proposed a semi-empirical analysis method for predicting energy absorption based on the research data. Feraboli et al. (2009) studied the energy-absorbing performance of composite specimens of different cross-section geometries and found that the small corner element has the highest SEA, and tensile fracture and tearing of fibers at the corner are the main energy absorption modes . Zhenyu et al. (2019) found that the failure mode of composite thin-walled composite channel section structures under low-speed axial compression is mainly composed of local buckling, corner cracking, and delamination. ...
... The material of the composite channel section specimen is TORAYCA T700/2510 (Toray Composites of America, Frederickson, Washington) carbon fiber/epoxy fabric. The results of a crush experiment on this specimen can be obtained from Feraboli et al. (2009). The composite channel section specimen was 63.5 mm in length and 45.5 mm in width, having 4.45 mm in inner radius and 1.65 mm in total thickness, as shown in Fig. 1. ...
... The damage parameters used for numerical simulation of intra-layer and inter-layer are listed in Table 2 ( Sokolinsky et al. 2011). The bottom of the composite channel section specimen was put into an epoxy resin base to ensure stability during the crushing process, as shown in Fig. 6 (Feraboli et al. 2009). Thus, a constraint was established between the fixed plate and the specimen, to simulate the same constraint conditions as the experiment. ...
A nonlinear progressive damage model was adopted to study the energy absorption mechanism of fabric composite channel section structures under axial quasi-static crushing loading. Based on continuous damage mechanics (CDM), intralayer and interlayer failure were initiated by the maximum stress and quadratic nominal stress criteria, respectively. The damage process of the material is described using the progressive damage evolution law based on the stiffness degradation method. The different failure modes exhibited by the composite channel section structure under different crushing displacements are analyzed in detail. The effects of geometric sizes and stacking sequences on the initial peak value, specific energy absorption (SEA), mean load, and failure mode are analyzed and discussed. The results show that thickness has a positive effect on the specific energy absorption and induces progressive failure of the structure. The initial peak force is a positive correlation function with respect to thickness and flange length. The flange length and stacking sequence have a significant effect on the crushing load response of the structure, and a reasonable stacking sequence can improve the crushing behavior of the structure.
... In the crashworthiness study of vehicles, optimization of bumper beam geometry is not a new topic. Over the past decade, numerous researchers have devoted time and effort to this development and the cross-sectional shapes of bumper beams can be diverse: closed-section, open-section, C-section, D-section, L-section, rectangular, and circular [14]. Hambali et al. [15] proposed a series of steps to help engineers with bumper designing, they stated that an optimal cross-sectional shape design of the bumper beam can improve structural stability and deformation resistance, and at the same time, it can increase the energy absorption rate of the bumper beam during impact. ...
The objective of this work is to analyze the influence of the cross-section of a bumper beam made of fully biodegradable composites. Flax/PLA bumper beams were manufactured with four types of cross-sections with different degree of roundness. Specimens were subjected to low velocity impacts and the post-impact behavior is evaluated under three-point bending tests. Results indicate that different cross-sections can be selected if the objective is to maximize the impact performance or the post-impact residual properties. The bumper beam with the higher roundness exhibits the best impact performance, while an intermediate section exhibits the best after impact residual mechanical properties.
... Thin-walled structures are widely used as energy absorption devices in automobiles, railway vehicles [1][2][3] and aircraft [4] to protect passengers from traffic accidents. Composite structures have attracted widespread attention due to their high specific strength, high specific stiffness and strong design ability compared to conventional metallic structures [5][6][7]. ...
Composite tubes have been widely used as the energy absorption device. In order to realize the fine crashworthiness design, it is necessary to perform multiple iteration calculations by the finite element analysis. However, the high-fidelity calculation of the composite damage model is time-consuming (a model with about 320000 elements requires 32 to 40 h of computation). Therefore, a novel equivalent method for crashworthiness analysis of composite tubes (namely EMCA) is proposed to improve the computational efficiency. The EMCA involving the failure mechanism of the composite can predict the total energy only based on the calculation in the limited progressive stage of a composite tube. Compared with the experimental and numerical results, the computational efficiency of EMCA can be greatly improved by 62-86%. Additionally, the illustrative examples are carried out to prove the effectiveness.
... They found that the flat plates could yield superior than angle and channel ones under the same progressive failure mode. However, Feraboli et al. [20] found that the small corner element was the most efficient in terms of SEA. In addition, Yang et al. [21] studied the crushing responses of 3D braided composite tubes with different radius of corners under compression and concluded that the energy absorption capabilities of square or rectangular tubes can be improved by using a reasonable design of the corner geometry. ...
... This led to the fact that the of entire tube was slightly lower than that of 4-corner tube. Similar finding was also reported in the studies of Feraboli el al [20]. The of the sum of flat side and corner (76.68 J/g) was lower than that of entire tube (85.6 J/g). ...
... Compression testing fixtures for flat side specimens[20]. ...
The cross-sectional configuration is one of the factors influencing the energy absorption performance of composite tubes under axial compression. Flat sides and corners are basic elements for the configuration. However, their contributions to the energy absorption have not been systematically compared. This paper presents a “press and cut” approach which allows to investigate the energy absorption of flat side and corner elements in a condition closely resembling axial crushing of a tube. Using this method, the crushing responses and energy absorption behaviors of flat side and corner elements in carbon fiber reinforced plastics (CFRP) square tube under axial quasi-static compression were investigated experimentally. The results showed that the corner elements had higher specific energy absorption (SEA) values than the flat side elements. The higher SEA value is attributed to the additional axial tearing fracture of the fronds developed at the corner and the suppression to delamination by the hoop tension force in the round corner. A modified analytical model based on Hussein’s analytical model was established to predict the mean crushing force of the flat side and corner elements. Finally, axial crushing experiments were performed for CFRP tubes with a cross section consisting 12 corners. The 12-corner tubes exhibited an about 18% higher SEA value than the square tubes while maintaining a similar peak force.
... The driving forces behind the widespread use of composite structures in thin-walled applications are their high strength, low specific weight and tailored fibre directionality which allow them to meet high performance requirements in applications for aerospace, naval, construction and automotive industries. Thin-walled structures can be designed with open or closed cross-sections (a few examples are given in references [1][2][3][4][5][6][7][8][9][10]). Those geometrically complex components are typically subjected to various loads, such as axial compression, bending, torsion and most often combinations of these. ...
... Motivated by the widespread use in marine engineering, the hydroelastic effect of flexible stiffened composite panels used in ship design under different slamming water impact velocities [15][16][17] has been studied extensively both experimentally and numerically. Undoubt-edly, the utilization of thin-walled structures as energy-absorbers through controlled damage processes under impact or crushing events has received by far the most attention [2,5,9]. The energy absorption capability for crashworthiness applications in automotive and aircraft structures has been investigated extensively, both experimentally and numerically, for various specimen geometries, materials, fibre arrangements and loading rates [18][19][20]. ...
Testing of carbon fibre epoxy hollow beam components was undertaken using digital image correlation and acoustic emission techniques. Static and fatigue testing was used to characterise the damage mechanisms of the components under two separate compressive loading cases. Firstly, the load was transferred via simple contact of a rectangular pusher plate, whilst in the second case the plate was bolted to the top surface of the beam. Digital image correlation determined the full field deformation and strain on the beams’ side while strain gauges validated the accuracy of the measurements during testing. Acoustic emission analyses provided a more in-depth inspection of the failure location as the first damage event was not visible from an external visual inspection. Acoustic emission captured a precise map of damage events which indicated the failure location at a point under the loading plate edge and centred at the corner of the beam structure. While DIC gives a full field view of strains on the component surface before and after failure, the acoustic emission analysis shows a higher sensitivity to the characterisation of damage, providing a more conservative and accurate estimate of the failure behaviour.
... The main focus is on reducing fuel consumption and thus emissions while increasing the safety of drivers, passengers, and pedestrians [5,7]. The need to meet such conflicting requirements increased the interest in lightweight materials [1,4,5,[7][8][9][10][11]. For example, reducing the mass of a BEV vehicle frame has a direct influence on the capacity and, thus, the mass of the batteries [1,4,5,7,10,12]. ...
... However, due to the occurrence of buckling, these results are not comparable. A comparison of the results of the flat-plate specimen and the profiles seem not relevant, as stated by Feraboli et al. [11]. The results obtained from crushing profiles can be different even from each other due to the profile shape, dimensions, and wall thickness. ...
... Moreover, the SEA calculation from the crushing component of the measured load leads to width-independent and consistent results. Even though the energy absorption determined here of the SEA M for flat-plate specimens and those for the profiles, as in Ref. [41][42][43][44], are different, as stated in Ref. [11], the general trend seems to be similar, which adds to the credibility of the results and the utilized method. ...
This study presents an investigation of the effect of fiber length, fiber mass content, in-plane fiber distribution, plate thickness, and loading rate on the energy absorption mechanism of discontinuous carbon fiber composite flat-plate specimens utilizing the crush property isolation technique. Similar crushing morphology is obtained for flat-plate testing as for discontinuous carbon fiber tubes. Fiber length and fiber mass content showed only a minor effect on the specific energy absorption (SEA). Results obtained for the in-plane fiber distribution showed to be consistent. SEA-values increased substantially with increased plate thickness. Loading rate dependency could be observed as a decrease in SEA when increasing plate thickness.
