Energy Absorption Of Composites Research Articles

Pre-stressed thin tubular composite energy absorbers for improved impact energy absorption

The study proposes pre-stressing techniques as applied to CFRP based composite thin-walled tubes with the intent of increasing energy absorption capacity. The energy computations for the tube with and without pre-stressing are compared using finite element based methodology. The study reveals that the use of pre-stressing in the form of applied internal pressure for the tube induces forces in the direction opposite to that of impact which needs to be overcome when the actual impact happens. The study also demonstrates that the strain energy required for initiating the damage in the thin-walled tubes increases appreciably under the influence of pre-stress.

The crashworthiness performance of stacking sequence on filament wound hybrid composite energy absorption tube subjected to quasi-static compression load

This study investigates the energy absorption response of hybrid kenaf/glass fibre-reinforced epoxy when subjected to an axial quasi-static compression load with the effect of three stacking sequence of hybrid kenaf/glass reinforced epoxy. To characterise and evaluate the physical and mechanical properties, the hybrid composite tube was compared with synthetic glass fibre-reinforced epoxy. The hybrid and synthetic composites tube sampling were prepared by using automated filament winding technique which it provides the process with a proper fabricating procedure, quality control and stable process due to the mixture/ratio of the fibre and resin volume controlled by the winding speed and fibre tension. Crashworthiness mechanism of hybrid and synthetic composite tubes specimen were discussed to understand failure modes behaviour and energy absorption characteristics in term of quasi-static compressive response. Four different failure modes were observed in crushing tests as fibre/resin fracturing, local buckling, brittle fracturing and delamination. In the view of fibre stacking sequence aspect, fibre volume fraction in the hybrid specimen (HTS45-A) is a highest compared to other specimen and at the same time alleviates the capabilities in progressive failure with the significant increase 28% of initial peak load and 68% of the energy absorbed compared to the glass fibre-reinforced epoxy tube. Meanwhile, the glass fibre-reinforced tube showed the greatest specific energy absorption characteristics with the lowest initial peak load value with stability in progressive crushing behaviour. Also, experimental results have showed that kenaf fibre could be utilised as a potential reinforcement material in hybridisation with synthetic glass fibre composites as energy absorption tube application.

Modelling of composite energy absorbing structures for automotive load-bearing systems

Due to the increasing demands for environmental friendliness and fuel economy of cars, the task of reducing their weight is becoming topical. One of the promising ways to solve this problem is the use of composite materials for the manufacture of automotive body. The body of the car is subjected not only to static and slowly changing dynamic loads, but also can be subjected to impact loading. Therefore, it is necessary to assess the effectiveness of the use of composite materials for the manufacture of elements responsible for energy absorption. The paper analyzes the features of energy absorption during the destruction of composite structures, describes the ongoing processes and gives recommendations on the design of composite front rails. To assess the effectiveness of the composite front rail, a simulation of process of its crushing is carried out. To confirm the performance of the design, a crash test of a car with a composite energy absorbing structure is simulated. The applicability and high efficiency of composite energy absorber are confirmed

Multi-objective optimisation of a honeycomb-filled composite energy absorber for subway vehicles

To meet the requirements of passive safety protection during vehicle collision, a honeycomb-filled composite energy absorber (HFCEA) was designed in this study. A finite element model was established and effectively verified using experimental data. To evaluate the effects of the outer tube thickness, diaphragm thickness and honeycomb strength on the specific energy absorption (SEA) and the undulation of the plateau force (UPF), a polynomial response surface method was employed. To optimise the crash performance of the structure, i.e. to maximise the SEA and minimise the UPF, a multi-objective particle swarm optimisation was performed. A critical honeycomb strength was determined, beyond which the composite structure loses its weight efficiency. The UPF could be significantly reduced by increasing the honeycomb strength and reducing the outer tube thickness. This shows that the proposed composite structure can serve as an excellent crashworthy device for railway vehicles.

Investigation on Composite Energy Absorbers of a Composite Fuselage Section Subjected to Vertical Drop Test

In the aircraft industry, crashworthiness design and certification phases have been and are going to be the most attractive topics for designers, mostly because of the increasing use of composites for primary structural components. It is well known that the cargo subfloor elements of the fuselage structure play a crucial role in absorbing the kinetic energy during a crash. In particular, the stanchions, or struts, are important parts for the structural response; as a matter of fact, they connect the fuselage frames to the cabin’s floor and, ideally, are expected to crush under a compressive force in order to dissipate the impact energy in a controlled way and, consequently, to minimize the energy transferred to the passengers. The aim of this work is to demonstrate, experimentally and numerically, the energy absorption capability of the stanchions, made of both composite material and aluminium alloy, of a full-scale 95% composites made fuselage section under a critical load condition, such as an emergency landing. A Finite Element model allowing estimating the passive safety capabilities of the designed struts has been developed and herein proposed.

Investigation of Hybrid Natural Fibre Reinforced Composite for Impact Energy Absorption

In this paper, the low-velocity impact properties of jute/ramie fiber reinforced composites were tested by drop weight method, and the effects of mixing ratio on impact properties and energy absorption of composites were also studied. A series of impact energies ranged from 2 to 20 J were applied on five composites including jute fibre reinforced composite, ramie fibre reinforcement composite and three hybrid composites. When the jute fiber reinforced composite material is mixed with the ramie fiber reinforced composite material, energy absorption capacity of ramie fibre reinforced composites were enhanced with hybridizing this two fibre fabric together. The damage area was assessed using an ultrasound c-scan instrument. The results show that the hybrid laminate with a volume fraction of ramie fiber of 55% has better impact energy absorption and impact resistance. It was found that hybridizating different fiber together can effectively solve the problem of insufficient rigidity of jute fiber reinforced composite material and high ramie of ramie fiber reinforced composite material.

High velocity impact behavior of Kevlar/rubber and Kevlar/epoxy composites: A comparative study

This paper presents a comparison of behavior and energy absorption of neat Kevlar fabric and polymer matrix composites under high velocity impact loading. Two types of matrices including rubber and thermoset (epoxy) matrices were used in order to study the effect of a hard and brittle matrix compared with the soft and flexible matrix on energy absorption of the composite. Moreover, two types of rubber matrix with high hardness (HH) and low hardness (LH) were used in this study to investigate the effect of rubber matrix formulation on impact resistance of composites. Ballistic impact tests were performed by firing a 10 mm hemispherical projectile onto neat fabric and composites in a velocity range of 30–150 m/s for two- and four-layer samples. Results show that the matrix affects the ballistic performance of composites significantly. Rubber matrix enhances the energy absorption of the fabric by keeping composite flexibility. Increase the number of layers for Kevlar/rubber composite results in better ballistic performance. On the contrary, the thermoset matrix leads to an inflexible composite that restricts the fabric deformation and has a negative effect on the fabric’s ballistic performance. Finally, damage mechanisms were discussed in detail for each sample.

Ballistic performance of Kevlar fabric impregnated with nanosilica/PEG shear thickening fluid

This study presents the response of fiber reinforced composite material composed of woven Kevlar fabric impregnated with a colloidal shear thickening fluid (STF) under high velocity impact loading. The STF was made by dispersing silica nanoparticles at 15, 25, 35 and 45 wt.% loading in polyethylene glycol. The effects of silica nanoparticle loading on energy absorption and ballistic limit were studied experimentally. Rheological results revealed that shear thickening occurred at all four nanosilica loading and higher loading showing the higher shear thickening at lower shear rate. SEM images confirmed good dispersion of nanosilica particles in the suspension. The results of the pull out test show that by increasing nanosilica loading, the force required to pull the yarn out from the fabric impregnated by STF increases. Impact resistance performance of Kevlar fabric is significantly enhanced due to the presence of STF. Although high velocity impact results show that by increasing nanosilica loading, the energy absorption of composites increases, but in high loading of nanosilica, the effectiveness of STF decreases. For further investigation, the energy absorption at the ballistic limit was normalized by the areal density of the neat and impregnated fabrics to give the specific energy absorption (SEA). It is found that the SEA of 15 wt.% nanosilica loading is lower compared to the neat fabric. Also the highest SEA turn out in the case of 35 wt.% STF/Kevlar composites in which the SEA is 2.3 times larger than those of the neat fabric.

Comparison of the impact damage resistance of non-hybrid and intra-ply hybrid carbon/E-glass/polypropylene non-crimp thermoplastic composites

This study aims to compare the low-velocity impact and post-impact properties of intra-ply hybrid carbon/E-glass/polypropylene non-crimp thermoplastic composites with non-hybrid carbon/PP and E-glass/PP non-crimp thermoplastic composites. Impact test was performed at four energy levels as 15 J, 30 J, 45 J and 60 J. Post-impact properties of hybrid thermoplastic composites were tested by compression after impact method for each energy level to understand the impact damage tolerance of intra-ply hybrid carbon/E-glass/PP non-crimp thermoplastic composites. The effect of hybridization on energy absorption of composites was not significant, while C-scan results showed that the intra-ply hybrid non-crimp thermoplastic composites had smaller impact damage areas in comparison to the non-hybrid samples. Compression and compression after impact tests results confirmed that the intra-ply hybridization increased the toughness of the composite laminates. Also, the residual compression strength/modulus increased with hybridization which indicated to damage tolerance.

An experimental investigation on high velocity impact behavior of hygrothermal aged CFRP composites

In order to obtain the effect of hygrothermal aging on the high speed impact resistance of carbon fiber reinforced composites (CFRP), ballistic impact tests using flat blades projectile were conducted on the T700/TDE-85 laminates subjected to artificial accelerated hygrothermal aging (70 °C, RH95%) for different durations. Short beam shear tests were conducted on the aged specimens to evaluate the interfacial properties degradation. The effect of hygrothermal aging on the energy absorption and ballistic limit of composites were discussed. It is shown that the moisture absorption rate of the composites is in agreement with Fick law, with an equilibrium moisture absorption rate of 0.74% at 1369 h. The interlaminar shear strength (ILSS) descends rapidly with aging time and the retention rate of interlaminar shear strength was 50.6% after 2000 h. The ballistic limit and the critical energy absorption of the composites declined notably with the increase of aging time. Due to the weakened fiber/matrix interface, the delamination failure area in rhombic shape is of increasing severity with aging time. The matrix cracking and fiber/matrix interface debond due to long-term exposure to hygrothermal environment reduce the high velocity impact resistance of the composites.

Can Plant-Based Natural Flax Replace Basalt and E-Glass for Fiber-Reinforced Polymer Tubular Energy Absorbers? A Comparative Study on Quasi-Static Axial Crushing

Using plant-based natural fibers to substitute glass fibers as reinforcement of composite materials is of particular interest due to their economic, technical, and environmental significance. One potential application of plant-based natural fiber reinforced polymer (FRP) composites is in automotive engineering as crushable energy absorbers. Current study experimentally investigated and compared the energy absorption efficiency of plant-based natural flax, mineral-based basalt, and glass FRP (GFRP) composite tubular energy absorbers subjected to quasi-static axial crushing. The effects of number of flax fabric layer, the use of foam filler and the type of fiber materials on the crashworthiness characteristics, and energy absorption capacities were discussed. In addition, the failure mechanisms of the hollow and foam-filled flax, basalt, and GFRP tubes in quasi-static axial crushing were analyzed and compared. The test results showed that the energy absorption capabilities of both hollow and foam-filled energy absorbers made of flax were superior to the corresponding energy absorbers made of basalt and were close to energy absorbers made of glass. This study, therefore, indicated that flax fiber has the great potential to be suitable replacement of basalt and glass fibers for crushable energy absorber application.

Low-velocity impact behavior of weft-knitted spacer fabrics reinforced composites based on energy absorption

Spacer fabrics are prefered to other types of textile fabrics in energy absorption applications due to existence of pile yarns. The particular geometry of spacer fabrics induce to increase resisting out of plane forces such as impact along their thickness. In order to investigate the low-velocity impact behaviour of composites reinforced with spacer fabric, weft-knitted spacer fabrics with different types of pile orientation and pile length were produced using E-glass yarns. Using produced fabrics and epoxy resin, composites samples were provided by hand lay-up method. Low-velocity impact test was carried out on the prepared samples based on a drop-weight method using spherical steel projectile. The indentation at maximum force was extracted as - comparative criteria used to calculate absorbed energy.The results show that the energy absorption of composites increases by increasing the pile density and pile length.

Flatwise Compression and Flexural Behaviour of Perlite/Sodium Silicate Composite Foam

Flatwise compression and flexural behaviour of perlite/sodium silicate composites made of expanded perlite and sodium silicate is studied using a new manufacturing method for applications of sandwich foam core materials. Sodium silicate content in composites (a perlite particle size of 2-3mm) was varied for a range of 0.1 - 0.3 g/ml and compaction ratio for moulding for a range of 2.0 - 3.0. Specimens under flatwise compression were found to be more capable for energy absorption than those previously reported for lengthwise compression, ascribing to appearance of densification stage following the initial cracking. Also, under flexural loading, energy absorption in composites after the initial cracking was found to be in operation, supporting their candidacy for wide applications where gypsum boards are dominant. It was deduced from both flexural testing results and fracture mechanism that compressive strength is higher than tensile strength, suggesting the future directions of mechanical performance improvement.

Mechanical characterization of novel latania natural fiber reinforced PP/EPDM composites

Novel natural fiber-reinforced polypropylene (PP)/ethylene-propylene-diene-monomer (EPDM) composites containing 0–30 wt% of short latania fibers (SLFs) were fabricated and tested. Measured ASTM standard tensile and Charpy impact properties were compared to those for PP/EPDM composites containing short jute fibers (SJFs) [1]. SLF composites displayed somewhat better tensile properties than analogous SJF composites. Moreover, as the SLF weight fraction was increased, there was a profound increase in composite energy absorption capability (EAC). In contrast, increasing SJF weight fraction resulted in a marked decrease in the composite EAC. Good qualitative agreement was found between measured EAC values for both PP/EPDM/SLF and PP/EPDM/SJF composites and calculated fracture toughness values. Scanning electron microscopy images of PP/EPDM/SLF composite fracture surfaces were used to characterize the relevant failure mechanisms and damage morphology. This study suggests that latania fibers hold promise as a composite reinforcement phase for applications where both tensile properties and energy absorption are important.

Effect of through-the-thickness areal density and yarn fineness on the mechanical performance of three-dimensional carbon–phenolic composites

An experimental investigation was performed to study the mechanical performance of 3D carbon/phenolic composites subjected to bending and impact forces. T300-3 k dry preforms were tufted using carbon threads of 396, 800, and 1600 tex. Also, the tufting densities varied from sparse density (tufted 16 × 16: areal density = 0.37 cm−2) to moderate density (tufted 11 × 11: areal density = 0.82 cm-2) and high density (tufted 5.5 × 5.5: areal density = 3.30 cm−2). The tufted preforms were then infiltrated by phenolic resin through the vacuum pressure infusion process. The three-point bending tests results revealed that the flexural strength loss of tufted composites ranged from 17 to 34%. In untufted composites, the specified crack grew quickly along the composite while through-the-thickness reinforcements stopped the crack growth and led to crack branching along the thickness of composite. With the presence of through-the-thickness yarns, damage behavior changed and the tufted composites exhibited a slower rate of decrease in the level of stress. These composites also showed higher levels of after-failure stress values. The experimental results of the impact test demonstrated that tufting had different effects on the energy absorption of composites. In a number of tufted composites, the energy absorption increased by 14.6% and in the other ones, it reduced by 8%.

Crush responses of composite cylinder under quasi-static and dynamic loading

Despite the abundance of studies investigating the performance of composite structures under crush loading, disagreement remains in the literature regarding the effect of increased strain rate on the crush response. This study reports an experimental investigation of the behaviour of a carbon–epoxy composite energy absorber under static and dynamic loading with a strain rate of up to 100s-1. Consistent damage modes and measured force responses were obtained in samples tested under the same strain rate. The energy absorption was found to be independent of strain rate as the total energy absorption appeared to be largely associated with fibre-dominated fracture, which is independent of strain rate within the studied range. The results from this study are beneficial for the design of energy absorbing structures.

Effect of fiber surface texture on the mechanical properties of glass fiber reinforced epoxy composite

The effect of fiber sizing and surface texture on the strength and energy absorbing capacity of fiber reinforced composites has been evaluated at two length scales using the macromechanical quasi-static punch shear test and the micromechanical microdroplet test methods. E-Glass/SC-79 epoxy composite laminates with four different fiber sizing formulations with various degrees of chemical bonding and surface texture have been investigated. The failure modes during perforation and different energy dissipating damage mechanisms were identified and quantified. The punch shear strength and the total energy absorption per unit volume of composite with hybrid sizing have increased by 48% and 100% over the incompatible sizing. These results showed linear correlations with the interphase properties reported earlier by the authors (Gao et al., 2011) and provided a methodology for developing new sizing by tailoring chemical bonding and the fiber surface texture at the fiber–matrix interphase for improving both strength and energy absorption of composites.

The effect of different boundary conditions on crushing behavior of hat-shaped polymer composite energy absorber

Side-door impact b eams are widely used in car doors to improve the passenger’s safety during the side impact. Fiber-reinforced polymer composite materials have a high specific strength and stiffness and are considered suitable candidate for this application. The aim of this study was to investigate energy-absorbing capacity of hat-shaped structures made from fiber-reinforced polymer composite materials at different boundary conditions. A finite element analysis model was developed using ABAQUS/Explicit code to achieve optimized fiber orientation and stacking sequence. Unidirectional E-glass fiber/polyester resin was used to construct hat-shaped beam energy absorber. Finite element analysis has revealed the optimized fiber orientations of [75/0/0/−75], [−75/0/0/75], [60/−30/30/-60], [−75/−30/75/30], [30/60/−30/−60] for quasi-static loadings, and [60/45/−45/−60], [45/−45/−60/60], [75/60/−60/−75], [−30/30/45/−45], [−75/−60/75/60] for impact loadings. Quasi-static bending as well as pendulum type impact test was carried out on specimens made with fiber orientation adopted from numerical analysis. Quasi-static bending test demonstrated that in fully clamped boundary conditions, composite layup orientation of [−75/0/0/75] showed maximum energy-absorbing capacity, but in other boundary conditions, composite layup orientation of [60/−30/30/−60] had the maximum energy-absorbing capacity. Contrarily, pendulum impact test for similar boundary conditions showed the highest energy absorption happened in fiber orientations of [−30/30/45/−45] and [−75/−60/75/60]. It was postulated that different modes of loading were the reason for this discrepancy.

Development of Composite Energy Absorber

This paper presents experimental investigation and numerical prediction of the deformation behaviour of several types of composite deformation elements, whose potential use is in public passenger transport. Experiments were conducted on two types of samples. First, on filament wound composite tubes with thermoset polymer matrix and on moulded thermoplastic corrugated plates. Tests have shown that the absorbed deformation energy of elements made from filament wound composite tubes depends on the laminate layup. Deformation elements made from moulded thermoplastic carbon sheets are also promising for parts of composite absorbers. The full-scale crash-test simulations (in the PamCrash software) showed that applied deformation boxes in the front bumper of the city bus can effectively absorb large percentage of the impact energy in the initial stage of the crash.

Analysis and Application of the Impact Absorption Behavior of the Composite Tube

Composite tube is one new kind of multi-material shell structures. It has both of metal and composite energy absorption advantage. In order to find the energy absorption characteristic of composite tube and put it into use, the Drop-Weight Tear Test (DWTT) was carried out. The LD2Y aluminum was chosen as the inner metal material which was wrapped fiberglass epoxy composite outside. During the test, the displacement signal and velocity signal, acceleration signal were got by piezoelectric acceleration transducer. Furthermore, the DWTT test of the composite tube was simulated in LS-DYNA, and proved the validity of the model by comparing the simulation results with the experiment results. We established the vehicle front longitudinal beam model with the material type of the composite tube, and carried out the simulations of whole car collisions in LS-DYNA according to FMVSS 208. Through the analysis of occupant head injury got from the simulations, we got the result that using the composite tube material could not only elevate the cars safety but also reduce front longitudinal beam weight effectively.