Crush Load Efficiency Research Articles

Investigation on the temperature dependent out-of-plane quasi-static compressive behavior of metallic honeycombs

Abstract This study investigates the effect of temperature on the out-of-plane quasi-static compressive behavior of metallic honeycombs by numerical and theoretical methods. Adopting a temperature dependent elastic-perfectly plastic constitutive relation, the temperature dependent out-of-plane quasi-static compressive mechanical performance of Al5052 honeycomb is studied with the finite element method. The results show that the plateau stress, peak stress and specific energy absorption (SEA) of Al5052 honeycomb decrease gradually with increasing temperature, while the crush load efficiency (CLE) and deformation pattern are temperature insensitive. Then, based on the numerical results in this study and super folding element theory, the temperature dependent theoretical models without fitting parameters for the plateau stress and SEA of metallic honeycombs are developed, respectively. These theoretical models are successfully verified against numerical simulations and experiments. Based on these theoretical models, the effects of parent material properties on the plateau stress and SEA at different temperatures are discussed. The results in this study provide useful guidelines in optimizing the choice of parent materials to fabricate metallic honeycombs with better energy absorption efficiency at different temperatures.

Effect of cut-outs on the axial crushing response of cap and open-end hybrid frusta tube

The present paper presents the computational analysis of the crushing response of AA-1080 cap and open end hybrid frusta tube, with and without circular cut-outs subjected to the quasi-static axial loading. The two concentric frusta tubes placed co-axially having different heights of 91.6 mm and 85 mm of inner and outer tubes respectively were considered as hybrid frusta. The frusta tubes thickness and semi-apical angle were assigned constant value as 1.15 mm and 5.71˚ respectively. The effect of radial distance (2.94 mm, 4.44 mm, and 6.94 mm) between two concentric tubes as investigated. The numerical simulations were carried out using finite element code LS-DYNA.The crushing behavior of hybrid frusta tubes was examined based on the response of the peak force (PF), mean force (MF), crush load efficiency (CLE), and energy absorbing capacity (EAC). The radial distance was found to have a major impact on the deformation behaviour and with an increase in radial distance, the CLE decreases. Moreover, the response of cut-outs on the performance of hybrid frusta was presented and analysed. Through having a cut-out on both sets of hybrid frusta, the CLE increased by 3% to 10% whereas the radial distance R3 was insignificant as per CLE perspective. Further, the reduction in PF was found 13% to 23% for cap end while 8% to 19% for open end hybrid frusta.

Crashworthiness performance of hybrid kenaf/glass fiber reinforced epoxy tube on winding orientation effect under quasi-static compression load

This research was aimed to study the effect winding orientation on the crashworthiness performance of hybrid tube. The specimens tested under quasi-static compression load involve of three winding parameters (θ = 30°, 45° and 70°) of hybrid kenaf/glass fiber reinforced epoxy and glass fiber reinforced epoxy as contrast specimen. The automated filament winding technique has been used in fabrication of hybrid and non-hybrid composite tube and crashworthiness performance was investigated experimentally. The effects of winding orientation on energy absorption capabilities and crashworthiness characteristic were investigated through quasi-static compression load and the result are compared with the glass fiber composite tube to justify the capability of hybrid natural/synthetic as energy absorption application. Hybridized samples proved to enhancing the progressive crushing capability as combination of local buckling, delaminate and brittle fracturing as progressive crushing modes.In the view of winding orientation aspect, the results of high winding orientation of hybrid composite tube elevated the crush load efficiency, specific energy absorption and energy absorption capability compared to glass composite tube (GFRP). The hybrid kenaf/glass composite tube with high winding orientation showed the best winding orientation to enhance the energy absorber characteristics as energy absorption application.

An experimental study on intraply fiber hybridization of filament wound composite pipes subjected to quasi-static compression loading

Abstract This paper aimed to explore the failure modes and crashworthiness characteristics of intraply hybridized fiber reinforced pipes (FRP) made of basalt and glass fiber reinforcements subjected to quasi-static compression loading. Experimental investigations were performed on various fiber orientation angles (±40°, ±55°, and ±70°) of the basalt FRP, glass FRP and hybridized basalt/glass FRP, fabricated by filament winding technique. Fracture mechanisms of pipe samples were discussed to understand failure modes. Three distinct failure modes as transverse shearing, lamina bending, and local buckling were observed in crushing tests. Hybridized samples proved to fix instability deficiency of pipes by exhibiting the progressive failure as combination of transverse shear and lamina bending crushing modes. Also, experimental results belong them within the range of pipes made of glass and basalt fiber data's as expected. In the view of fiber orientation aspect, decrease in winding angle resulted with the significant increase of energy absorption capability of all pipes. The pipes made of glass fiber showed the best specific energy absorption characteristics with the lowest crushing load efficiency.

Crushing behavior of a unit cell of CFRP lattice core for sandwich structures’ application

Sandwich structures made of composites are designed mainly for higher and efficient load capacity. Mostly, the use of composite materials in lattice core sandwich structures is limited to the face sheet; whereas, the core is usually made of metals due to the difficulty in producing the FRP lattice shape. A sandwich with a core made of FRP is believed to be lighter and better in terms of specific strength and absorbed energy. In order to manufacture the sandwich core, several methods and techniques were developed based on the designed core profile. In this paper, the core was extracted (using laser cutting) from the standard flame retardant carbon fiber hat stiffener. Four values of the strut angle α were considered (α=45, 60, 75, and 90°). Crushing tests were performed using Instron Compression machine and a load cell of 5kN capacity. Similar post crushing profiles were obtained for all the specimens. However, the peak load is being shifted upward. Improvements of 75% and 54% were recorded for the peak and the average crushing loads respectively. It is worth remarking that the crush load efficiency was kept constant during the tests. The energy and the specific energy absorption showed that the unit cells with 90° are at advantage since it is almost 53% higher than that of the 45°. For the effect of filler, the tests results show how important it is to fill such thin skeletal structures.

The effect of FRP thickness on energy absorption of metal-FRP square tubes subjected to axial compressive loading

Hybrid square tubes made from S2 glass/epoxy composites and 304 stainless steel with different fiber orientation, stacking sequence, and thickness are tested under quasi-static loading. The thickness of composite section is identified as an important parameter that can change the crushing mode of stainless steel tubes and also, in some cases, lower its energy absorption due to change in plastic deformation. In addition, a new triggering design is introduced that can increase the crushing load efficiency (ratio of mean crushing to maximum load) up to 13% compared to a chamfered trigger.

An experimental investigation into crushing behavior of radially stiffened GFRP composite tubes

State-of-the-art studies of the crushing of composite tubes reveal different factors affecting their crashworthiness. Of those factors, the geometrical property of the tube is of great interest. In the current study, four different categories of tube cross-sectional geometrical properties were tested under a quasi-static crushing scenario to investigate the best cross-section in terms of the crushing load and the energy-absorption capacities. A woven GFRP consisting of eight layers was used to manufacture the tubes. The results showed that reinforcing the circular tube with radial GFRP webs could improve both the load-carrying capacity and the specific energy-absorption capability. The stability of the crushing process is of great interest in automotive applications. It was found that introducing the geometrical reinforcement inside the tubes could have a positive effect on the stability of the crushing during the loading, the average crush load, and the crush-load efficiency.

On a new crush trigger for energy absorption of composite tubes

A new crush trigger, called crown trigger, is introduced at one end of carbon-fibre-reinforced polymer circular tubes. Quasi-static compression tests are performed on the tubes to investigate their energy absorption characteristics. It is observed that all tubes are crushed in a brittle fracturing mode. Both crown trigger and bevel trigger can effectively control the position of crushing initiation, reduce the peak load and increase the crushing stability. It is also found that the tube wall of each specimen is delaminated mainly into three layers. The relatively intact exterior layer may constrain the axial splits of the middle layer, make the lamina bundles break off near the base, slow down the central wall crack propagation and thus eliminate a low-performance failure mode. As compared with the bevel trigger, the crown trigger provides nearly the same specific energy absorption but 18.4% lower specific triggering stress and 21.2% higher crushing load efficiency.

Effect of the SMA Trigger on the Energy Absorption Characteristics of CFRP Circular Tubes

Quasi-static compressive tests were performed on carbon fiber reinforced polymer (CFRP) circular tubes to examine their axial crushing behaviors. Stable progressive crushing processes with brittle fracturing crushing mode were observed during the experiments. It is found that the crushing triggers including the ply drop off trigger and the shape memory alloy (SMA) trigger introduced in the specimens can efficiently initiate a stable progressive crushing process and significantly improve the specific energy absorption (SEA) as well as the crushing load efficiency (CLE) of the specimens. It is important to mention that the SMA trigger provides 37.2% increase of the SEA and 28.0% increase of the CLE, respectively, as compared with the specimens without a crushing trigger. Moreover, the SEA and the CLE of the composite tubes with the SMA trigger are 22.8% and 4.3% higher than those of specimens with the ply drop off trigger. In addition, the significant improvement of the SEA and the CLE is achieved with only a little increase of the initial peak-specific crushing stress.