Hybrid reinforced thermoset polymer composite in energy absorption tube application:A review

A.B.M.Supin,S.M.Spun,M.Y.M.Zuhri,E.S.Zinudin,H.H.Y

aDepartment of Mechanical and Manufacturing Engineering,Universiti Putra Malaysia,43400,UPM,Serdang,Selangor,Malaysia

bLaboratory of BioComposite Technology,Institute of Tropical Forestry and Research Products(INTROP),Universiti Putra Malaysia,43400,UPM,Serdang,Selangor,Malaysia

cDepartment of Mechanical Engineering,Universiti Teknologi Petronas,32610 Seri Iskandar,Perak,Malaysia

Keywords:Energy absorption tube Hybrid composites Collapse behavior Crash worthiness

A B S T R A C T The custom of hybridization fibre composite in energy absorption tube application has gained the attention of structural crash worthiness in composite material industry.Thus,the approach of this review is to understand the effect in hybridization within metal/synthetic fibre composite,synthetic/synthetic fibre composite and nature/synthetic fibre composite as energy absorption tube,which reflects on the energy absorption characteristics and crash worthiness behaviors in previous the study.By way of instance,a wide range of methodology and particular parameter in previous study such as the effect in fibre arrangement,matrix polymer,technique of fabrication, fibre treatment(natural fibre),design in geometry/cross-section and others mechanism of hybrid fibre composite tube are highlighted which to comprehend the capability of the mechanical performance and collapsible behavior as sacrificial structure in high-performance structure applications.Moreover,in the recently studies there have been many of the research regarding structural materials as energy absorption tube has been introduced such as metal/matrix composites,new alloy metals and polymer composites which intended to evaluate the performance of these materials into circumstance in loading and impact characteristic.Therefore,this review article is trying to explore the research articles related to the effect of hybridization fibres and thermoset polymer as reinforcement for energy absorption tube research and expected would provide an information and idea which to expend the knowledge in future study of hybridization effect for energy absorption tube,moreover the development for future potential as new hybrid composite fibre materials from the natural/synthetic fibres reinforced composite material in employing of high-performance energy absorption tube application is still less discover and highlighted.

1.Introduction

In early 1970 the awareness of thin-walled energy absorbing tube for crash worthiness applications has been growing due to the increase of the safety-conscious environment in major transportation industry such as automotive,airlines,and aerospace[1].The thin-walled tube structures in energy absorption tubes nowadays are fabricated from a various strong material such as metallic,synthetic fibre and hybrid composite fibre which reinforced with various type of polymer.Therefore,the applications of thin-walled structure in aviation industry has majorly applied as webbed fuselage structures[2],steering columns[3]and landing gears for helicopters[4],meanwhile the application in high performance motors port[3],automotive[5],marine[6]and aerospace application[7]and other vehicles,predominantly was dedicated as the nose cone for formula-one cars,the front rails in motor sport vehicles and the crush absorber of trains and cars[8,9]which has been known as frontal rail tube or frontal longitudinal tube[9]where it was function and ability in crash worthiness,deformations and structural stability,which will also exhibit in durability,strength and fatigue characteristics[3,4].The basic awareness into designing the hybrid energy absorption tube into certain criteria of engineering design is illustrated in Fig.1.There was no single material may be found that can meet the ultimate desirable of energy absorption tube properties,thus to combine them in ways that retain the desirable attributes of both is the way forward to minimizing mass or cost,or maximizing some aspect of performance.Therefore,in basic principle of composite structure,any two distinct materials can be combined to make a composite structure,they are also can be mixed in many geometries structure.(see Tables 1-3)

Energy absorption tube is generally deformed of its primary structure,besides the additional energy absorbers can be unified to improve the crash behavior,which can be created on different material and parameter.There are two main categorized of energy absorbers in transportation application,where the first is the reversible energy absorber which used as hydraulic dashpot or elastic damper,and anotherone is irreversible energy absorber,like thin-walled energy absorption tube where it functions to dissipation the absorbed energy and collapse into plastic or ductile mode behavior[12,14].In the normal behavior of metallic energy absorption tube materials such as mild steel and/or aluminum,the energy is generally absorbed by plastic deformation mechanism[4-7],and most of the studies of metallic thin-walled energy absorbing tube can be improved by using a filler material(foam filled component)[8-10].Meanwhile,the Polymer Matrix Composite(PMC) fibre composite is naturally brittle and able to dissipate energy through a different combination of collapse mechanism through inversion or splitting deformation modes[11-13].The collapse behavior for composite fibre materials in the energy absorption tube commonly collapses into progressive crushing and fracturing behavior modes[4,5].

Consequently,several effects study of crash worthiness parameters on most of the composite thin-walled energy absorption tubes are focuses on cross-section tubes geometry[12,17],technique of manufacturing[19,20], fibre orientation[21,22],laminate stacking sequence[23,24],triggering mechanism[19,25]and wall thickness which significantly increase the initial peak load,lightweight,strong and also lower the stiffness of the structure under usual working situations[13].And numerous researchers aims improving their properties,therefore the light alloys is the best achieve of the single-material,even though alloys light but polymers have much lower densities.Due to a continuing research study of thin-walled tube, finding a new or alternative material from sustainable resource such as natural fibre to develop a high performance structure in term of hybridization effect as hybrid composite energy absorption tube are become more interesting and veryless in the previous study.Moreover,the hybrid composite in energy absorption tube study such as synthetic/synthetic fibre reinforced polymer and metal/synthetic fibre reinforced polymer are recognize that the hybridization effect will enhance the capability of crash worthiness and amount of energy absorbed,therefore the hybridization concept from other fibre such as hybrid nature/synthetic fibre composite will elevate the new chapter of development into high-performance energy absorption tube study.

Hence,in this review we will introduce the current findings on the hybridization effect of variety material and PMC composite and shown various crash worthiness behaviour and various optimal configurations affect in thin-walled energy absorption tube.Therefore,the hybrid composite in energy absorption tube study such as synthetic/synthetic fibre reinforced polymer and metal/synthetic fibre reinforced polymer are identify enhancing the capability of crash worthiness and amount of energy absorbed,therefore the future hybridization concept study from other fibre such as hybrid nature/synthetic fibre composite will elevate the new chapter in development of high-performance energy absorption tube study.Moreover,the future study of hybrid materials which consist the natural fibre appeared as a prospective environmentally friendly and cost-effective substitute to synthetic fibre reinforced composites[26-28,71].

2.Hybrid composite

Hybrid composite materials are consisting of two constituents at the nanometer or molecular level.In the study by Thomas[37]of hybrid compounds,he has specified commonly one of these hybrid composites is inorganic and the other one organic in nature.Thus,the constituents of traditional composites exhibit in macroscopic level,which leads to homogeneous material characteristics in concerning the two original phases or new properties.Therefore,the hybrid composite can be classified into properties of the mixture in a regular or random manner,the sandwich as core-shell,laminate/layering layer,and reinforcement(Fig.3)[30,38,93,135].Although a numerous research papers which currently dominated from metallic and polymer matrix composite(PMC)materials.Meanwhile the development of hybrid biocomposites which incorporation of several different types of natural fibres into a single matrix is less.Due to the performance of hybrid composites which is considered some of the individual component is more favorable balance between the inherent advantages and disadvantages.Therefore,the hybrid composite that contains two or more types of fibre will beneficially complement with what is deficient in the other.The hybrid composite strength depends upon the properties of the fibre content,length of distinct fibres, fibres orientation, fibre to matrix bonding and fibres sequence arrangement of both the fibres.Thus,the approach of developing new metal alloys,new polymer chemistries and new compositions of glass and other PMC materials it definite will reflect with additional cost and uncertain process.An alternative is to combine two or more existing materials to allow elevate the properties of hybrid energy absorption tube(Fig.2).

The failure strain of individual fibres will justify the strength of the hybrid composite and highly strain compatible fibres will determine the maximum hybrid results.Consequently,the concern for major applications in composites structural is the reduction in the cost of production and factor in the weight-to-strength are the main reason researchers are exploring the possibility of using hybrid synthetic and natural fibres[39,84].The hybridization method for altering the balance mechanical properties structures that include both types of material,for instance,metallic and Fibre Reinforced Polymer(FRP).The hybrid structure is a mixture of the required properties of each material,such as the ratio of strength to weight,strain to the displacement of the composites and ductility and stable plastic deformation mode of the metals and the goal was to increase the failure strain,ductility,and toughness.Therefore the problem of selecting the type of compatible fibres and the level of their properties is a most prominent aspect when designing and producing hybrid composites[33,102,106,110].

Table 1 Material properties of hybrid energy absorption tube study under axial compression load.

Table 2 A comparative study of the properties of polyester,epoxy and vinlyester resin.

Table 3 Fabrication technique of the Hybrid bio fibre composite thermoset in energy absorbing tube study.

Besides reinforcing solitary fibre composites,there was a several improvement of fibres were combined to a matrix leading to the development of hybrid composites where the properties of the composites are the mixture of properties of individual fibres.In an instance,hybridization in natural/synthetic fibres gives advantages to the utilization of properties the distinct fibre to enhance the properties in composites structure[22,23].Which the properties of the hybrid composite influenced by not only on the properties of the distinct fibre but also contribute by the possessions of the matrix as interfacial adhesion of fibre and matrix in the hybrid system[42].From study by Sanjey et al.[43]the natural fibre reinforced composite require low maintenance,high stress to weight ratio,high corrosion,impactresistance [15],nonconductive,avoid electrical hazards,reduced cost,easy installation due to light weight and fire retardant which it can adapt to be an excellent composition in the hybrid composite.

In general,the purpose of bringing two fibre types in a single structure composite such nature/synthetic hybrid fibre would bring an improvement of both fibres and mitigate some disadvantages[30,33].As well knows,the composites fibres are used in varies major industry for aerospace as a part in tails,wings,propellers,in sport equipment's such as bicycle frames,boat hulls, fishing rods,storage tanks,baseball bats,ice skating boards,door panels,for automobile industry,in construction material for buildings,and marine application forhull and superstructure[43-47].The natural fibre composite materials in the hybrid composition are used in a number of consumable goods and it was possible extensively will use in aerospace industry,body armor equipment,and ballistic composites components for the military when bond with the aramid fibres which strong synthetic fibres and class of heatresistant[28,30].

3.Crash worthiness criteria for energy absorption tube

The major criteria of thin-walled energy absorption tubes are derived as lightweight and having crash worthiness ability.Generally,to design the best crash worthiness tube of energy absorption as well as lightweight,there are several criteria must be fulfilled at the same time,thin-walled tube requires the specific energy absorption,post crushing integrity,and energy of the constituent materials( fibre and matrix).Therefore,different study and methods have been offered and produce various kinds shape and geometry design to reduce the initial peak load thus enhance the crush force efficiency[12,31].Generally,energy absorbing systems should be cost-effective,minimal weight,and support simplicity of manufacture and installation,meanwhile to measure the energy absorbing characteristics in collapsed under axial compression,the following parameters are obtained with reference to Fig.4.Substantial amounts of energyare absorbed in both progressive folding and progressive crushing[16,32-36].However,it is essential to understand the basis of a measure of the collapsibility that was the dependence of either mode on geometrical,microstructural and testing parameters.Therefore,the definitions below are the definition and technical terms based on the main features of crushing in composite tubes.

3.1.Absorbed energy

The total work is done or absorbed energy,EAabseither of progressive crushing or folding in crushing under static or dynamic compression load.The total absorbed energy,Eabsis equal to the area under the load-displacement curve,where:

respectivelyFandδare the crushing force and crush distance[20].

3.2.Mean crush load

The mean crushing load is the average crushing load over an energy absorber that deforms in a stable manner,which is defined by averaging the absorbed energyEabsover the crush displacement(δ).

3.3.Crush force efficiency

The Crush Force Efficiency(CFE)is the ratio mean for crushing force(Pm)which is divided by the peak crushing force or initial peak load(Pmax):

3.4.Specific energy absorption(SEA)

The area under the load-displacement curve(Fig.5),is the total energy absorbed which has been known asSEA.This criterion is used in the design of structures and most important characteristics of energy absorbersEAabs.The total energy absorbed can be plotted into two regions(pre-crushing and post-crushing)with different masses and it can be calculated by:

where m is total mass of the specimen/structure undergoes deformation.

4.Mechanical properties of hybrid composite tube

Performance of the hybrid interface study by Zhang et al.[56]was performed an investigation of the mechanical behaviors on the hybrid effects of the natural and synthetic fibres composites with the content of glass fibre in the mixture of unidirectional flax and glass fibre reinforced,Zhang et al.[56]has found that the stacking sequence effect obviously stimulated the mechanical properties and the performance in fracture toughness and shear strength.Meanwhile,a study of banana fibre in jute/epoxy composites by Boopalan et al.[57]shows that banana fibre in jute/epoxy composites of up to half percentage by weight has resulted increasing the mechanical and thermal properties and decreasing the moisture absorption property.In general,the purpose of hybrid composite fibre concept is to maintain the advantages of both fibres and improve some disadvantages.With respect to the above aspects,the hybrid composite materials represent an excellent possibility to design hybrid nature/synthetic reinforced polymer as absorption tube with requirements in dynamic behavior[21,34,64-66].

Thus,researchers are continuing to explore the hypothetically of using hybrid synthetic and natural fibres in composites for structural in major applications[41-43].The most used of synthetic fibres in hybrid composite reinforced are carbon,aramid,and glass.Fibreglass is a lightweight,heavy-duty and robust material,besides the material is characteristically far less brittle and its raw materials are too much cheaper,though strength characteristics are somewhat lower than carbon fibre[49,53].From previous study,there are numbers of factors that could affected the energy absorption capability of composite tubes such as fibres material[5,44]type of resin[45,46], fibre orientation[68,69],geometry/tube design[48-50]and technique of fabrication[72].The method in the study of crushing characteristics of composite tubes in static or dynamic crushing will help to understand the behavior and collapse integrity of composite tubes effectively[73].Besides,there have a number of studies have been showed on the hybrid composite material to understand the effect of hybridization of varies fibres and the mechanical properties to the application of energy absorption tube[39,40,51,53-56,108,109,138].The tensile strength of hybrid natural/synthetic fibre reinforced composites has been studied to understand the function of volume fraction and fibres orientation.The concept of hybridization of the reinforcement in nature/synthetic fibre composite demonstrate in several studies have obtain greater tensile strength due to the low density of the natural fibres when compared to individual type of natural fibres reinforced[39,57-63].There has wide hypothetically of using hybrid synthetic and natural fibres in composites for energy absorption,which will influence various mechanisms in the energy absorption as sacrificial tube.

There was always known that natural fibres and synthetic fibres are quite matched as a reinforcement to produce the hybrid composites.The hybrid composites usually demonstrate a significant improvement in any area of strength.A study by Yahaya et al.[87]has reported that variety of hybrid structure such as kenaf that already being used in hybrid with synthetic materials such as glass,carbon,and polyethylene terephthalate(PET).Meanwhile,a hybrid study by Athijayamani et al.[53]has given a proof by experiments on Roselle/sisal-polyester composites which the result achieve have resulted in an improvement in properties of the composites structure by adding the carbon fibre[41].Otherwise,for mechanical property analysis,the study by Ahmed et al.[88]was carried out woven jute/glass fabric hybrid composite and properties of another hybridizing of synthetic glass- fibre with natural fibres such sisal,bamboo,coir,oil palm and banana fibres in thermoplastic and thermoset matrices has significantly enhanced the mechanical,thermal,moisture absorption and weathering properties[61].Furthermore,the dynamic study by Hani et al.[89]has explored of hybrid(woven coir/Kevlar)composites in high-speed impact penetration,hence the data concluded that hybridization in the dynamic impact has signification contribution through the structure strength and resistance through impact forces.

4.1.Effect of fibre and resin

The mechanical performance of an FRP's composite materials basically depends on three major factor such as strength and modulus of the fibre,strength and chemical stability of the resin,and the effectiveness interface bonding between resin and fibre[73-75].To achieve the effective stress transfer,the length of the fibre is also should be in above the critical length which it also represents a decent interfacial bonding effect between fibre and matrix.The resin is known as a solid and highly viscous substance which originate from plant or synthetic which typically transformable into polymers.A polymeric material is an adhesive of polymeric substance with viscoelastic behavior,capable of joining adherents together by surface attachment where strength,stiffness and fatigue life must be maximized at a minimum weight.It can categories into thermoplastics,thermosetting resins,elastomeric compounds,and natural adhesives such as bio-based resins,or bioblends,obtained by replacing part of a petroleum-based resin with natural bio-resin.Commonly known thermoset polymers as polyester,epoxies,and phenolic.And for thermoplastics have known by name polyethylene,polystyrene,polypropylene,and many others and those polymers have different properties of chemical structure[73,75,76].Commonly numerous kinds of polymers have been applied in natural fibre composites as matrices.Therefore,the reinforcement effect of the fibres and resin/matrix may vary widely in application.

There are more study[90,91]prior an optimizing the fibre/matrix adhesion,treatment and others modification treatment on physical fibres to improved fibres in composite structures to have better properties than untreated composite fibres.Meanwhile,a study by Sreekummar et al.[103]has focused on chemical and physical modifications of sisal fibre to improve the interfacial bonding of sisal with the polyester matrix.Finally,the combination of the excellent chemical resistance,thermal and mechanical properties of epoxy resin system known as Vinyl Ester resins.It has better moisture resistance than epoxy where it also widely used for new applications in thermoset resins because of several factors such as better mixture with nontoxic catalysts like polyester resins,excellent wetting characteristics,sustain a high elongation at moderate and high heat temperatures,and very good heat aging properties[90].

4.2.Effect of fibre orientation

Besides the important resin system in the composition of the composite structure,other major properties of fibrous composite materials are also must be considered.The main major properties of fibrous composite materials are strongly hooked on several important parameters such as fibre diameter, fibre length,the volume fraction of fibres and alignment and arrangement of fibres orientation, fibre length and fibre content determining their mechanical performance[37,80,95-98,125].Alterations in fibre form will contrast in specific energy with the alterations in fibre form,e.g.chopped random swirl and oriented unidirectional continuous fibres[4,94,99].Numerous experimental studies in composite thin walled tube structure design and energy absorption relationship was indicated the most basic design parameters are measured from tube wall thickness and fibre orientation.Thus,the study of the energy absorption composite structure shows that increase in energy absorption performance of composites tube due to the fibres oriented in circumference direction has to affect various failures mechanism[30,36,47,82,91,92].

The effect of fibre orientation study in energy absorption tube was investigated by Spenser and Hull[112]have found the composite pipes wound at 35°,45°,65°,and 75°have shown that the deformation and failure mechanisms which were strongly dependent on winding angle due to micro-mechanisms associated with deformation,wee page,and fracture.Meanwhile,a study by Mahdi,Hamouda and Sebaey[68]in several different fibre orientation(0°/90°,15°/-75°,30°/-60°,45°/-45°,60°/-30°and 75°/-15°)in unidirectional wrapping mat of thin-walled tube composite has achieve the fibre orientation 15°/-75°and 75°/-15°are being best result in load capacity and energy absorption.Meanwhile,Swolfs,Gorbatikh,and Verpoest[30]and Lee et al.[113]have reviewed about basic mechanisms of hybrid effects which to determine of mechanical properties is challenging due to the synergistic effects of both fibres.Thus,many configurations of the low elongation and high elongation fibres of hybrid effects can be described as state-of the-art models or optimize the design in hybrid composites.Moreover,the study by Mahdi,Hamouda,and Sebaey[68]of capability energy absorption FRP tube in designs geometries with wet wrapping E-glass weaved fabric and epoxy resin has been reported shows different fibre orientation significantly influenced the energy absorption capabilities.

4.3.Effect of fabrication technique

There are numerous methods for fabricating composite components.The selection of the method in fabrication for a particular part is the most crucial prior to the part design and end-use or application.Hand layup is the most basic fabrication method for thermoset composites.Subsequently,the structure or component from composite material or hybrid composite materials have developed the evaluation of new modern techniques of fabrication such as vacuum bagging[114],autoclaves[75],Resin Transfer Molding(RTM),Vacuum-Assisted Resin Transfer Molding(VARTM),Resin Film Infusion(RFI),injection molding[115], filament winding[116,117],pultrusion[31],and many other to produce a strong and reliable composite structure or component in major composite fibres[52,96].Throughout the process of design and evaluation of new structural into energy absorption tube,the component tests are often conducted prior to fabrication of the entire structure has focused on the effect ply orientation and different composite materials[118].The behavior of the energy absorption properties due to collapsible modes of composite materials are basically can be tailored,thus making the tube appealing is an option a substitute,it was of more important in applications is the value of energy has been absorbed is crucial[119].Though in composite energy absorption tube the capability and advantage of technology in the fabrication of thin-walled tubes a less discuss[120,122].

Filament winding is a continuous fabrication method which has emerged as the primary process for composite cylindrical structures and can be highly automated and repeatable,with relatively low material costs.Previously,the processes for fabricating energy absorption tube are initially selection of type continuous reinforcements( filament,wire,yarn,tape,or other)with a matrix material(see Fig.6).Warrior et al.[67]have studied the effects of boundary conditions on the energy absorption of thin-walled polymer composite tubes under axial crushing where the specimen of the thin-walled tube was fabricated with continuous filament random mat glass/polyester composite.Meanwhile,Xu et al.[73]have a study of five types of Carbon Fibre Reinforced Composites(CFRPs)tubes were manufactured by filament winding method and investigated their crash worthiness performance and from the conclusion,it found that fibre arrangement in tubes fabrications was helpful to obtain higher in energy absorption.

Different kinds of circular tubes made of carbon,Kevlar,and carbon-Kevlar hybrid fibres composites with epoxy resin have been investigated by Kim,Yoon and Shin[121].The tubes were fabricated by wrapping the prepreg material around a circular steel pipe crushing to observe the behaviors of composite circular tubes with different reinforcing fibre.In wet winding process of cylindrical and corrugation geometry of composite tube has been fabricated by Abdewi et al.[116]found that the comparison of cylindrical composite tube and corrugation geometry radial corrugated composite tube exhibited good energy absorption capability than circular composite tube due to radial corrugated composite tube design have high positive effect in eliminating of sliding of the structure.

4.4.Effect of geometry

To design the hybrid composite components varies of the factor must be considered such as properties of the fibre,matrix,and interfacial adhesion between the fibre and matrix.Furthermore,to fulfill safety and lightweight requirements criteria in energy absorption tube,the extensive study has been carried out to evaluate the highest value of energy absorbed and collapse behavior into the various cross-sectional tube such as square tubes,conical,corrugated and many others[50,56,85,101].The attributes or criteria in determine the superior value in designing of the energy absorption tube are conflicting numerous objective functions where it can defined in varies criteria such as the highest energy absorption value,initial peak load,crush force efficiency(the ratio of mean load to maximum load),mass of the structure and deformation.Therefore,to optimize design majorly in thin-walled structures for energy absorption tube from various types of materials requires understanding their main weaknesses,which predominantly in high initial peak load of local static force or dynamic impact force.

In view of this,the hybrid thin-walled tubes in composite materials with different geometry such as circular,square,rectangular and conical tubes[29]have been widely explored as energy absorber due to the contribution of tube design and excellent energy absorption structure instead ofsolid beam structure[4,14,82,90,91].The study of metallic energy absorption tube,by Souzangarzadeh,Rezvani,and Jahan[123]have performed the design of the conical aluminum tube where the result has indicated design variables included wall thickness,lengths of sections,and taper angle mechanism are proportional to increasing and optimization of the energy absorption capability.Moreover,Thronton Harwood et al.[73]has indicated thatSEAof the sequence of energy absorption in FRP tube is obviously increase upon the relative density which the rectangular are less affected compared with square and round is a highest effected.

Meanwhile,the research study by Cheol et al.[75]study were comparing energy absorption characteristics of the hybrid tube with those of pure aluminum and composite tubes shows that the hybrid tube,which is lighter weight than the aluminum tube,showed a good energy absorption capability.And from Reuter and Tr?ster[132]study on the crash worthiness of circular hybrid Aluminium/CFRP tubes have found the mixture of energy absorption mechanisms of its pure materials and the specific energy absorption is higher than a pure aluminum structure.Moreover,in the study of Mahdi and Sebaey[124]and Sebaey et al.[133]have designs of hexagonal/octagonal composite energy absorption tube and conducted an experiment of the crash worthiness,shows that failure mechanism in both designs has attribute significant various failure mechanism collapse of carbon/epoxy and aramid/epoxy composite materials which affect the improvements in the stroke efficiency,the crush load stability,the average crushing load,the energy absorbed and the specific energy absorption as well.Otherwise,the strength of polymer composites can be achieved while reinforcing natural fibres under different conditions,such as using various chemical treatments on the fibres and hybridization with synthetic fibres.

5.Collapse behavior

Various types of composites materials and structures which occupied with passengers or transported cargo have significantly experienced the forces of progressive deformation and stable collapse[111-113].In the previous research,there is numerous attention focused the crushing behaviour of non-hybrid shell composites and can be derived that the composite materials absorb high energy,and behave fracture as a failure mechanism rather than plastic deformation[137].Basically,there are exist two types of failure mode mechanisms in normal composite FRP tubes where the response to the progressive crushing under axial compression which it will suit with the hybrid composite fibre capability of tailoribility as the hybrid fibre material to required structural applications[114,115].The first mode observes is called a progressive folding which similar to ductile metal and plastic tubes.

The second mode is the combination of fracture,where most of the energy absorption composite tubes fail initially into microfracture and propagate to macro-fracture at the post-crushing stage of collapse which called a progressive crushing mode[24].Meanwhile study from Mamalis et al.[136]have identified three distinct modes of collapse where it referred to the properties of the fibres,matrix and fibres arrangements related with tothe geometry of the shell tubes:(Mode I)end-crushing or delamination mode,(Mode II)mid-length collapse mode,and(Mode III)mixed mode of collapse.And the study by Weaver and Ashby[140]of several anisotropic materials cross-sections shapes,has conclude that the three main failure mechanisms of tubular structure under load or force,which was local buckling,global buckling and yield/fracture(Fig.7,Fig.8)[129,139].

5.1.Crash worthiness

Crash worthiness is the term that uses in major safety testing of aircraft and vehicle structure,which the term is the ability of a structure to protect its occupants during an impact.A number of criteria are used to evaluate crash worthiness prospectively,including the deformation patterns of the energy absorption.Crash worthiness of metal tubes has been studied by the vast majority of researchers[104,105,116,126].Energy absorption mechanism in metal tubes normally behaves with plastic deformation mode due to the progressive folding formation[142].Consequently,FRP composites have absorbed energy unlike metals which absorbs energy by plastic deformation,but normally dominated through failure modes of progressive end-crushing mode,unstable local tube wall buckling mode and mid-length collapse fracture,frond bending, fibre fracture and extensive micro cracking development[5,48]and Zhu et al.[143]has performed in the study of CFRP crushing behavior and observed the CFRP composite is likely associated with the highest energy absorption in failure mode progressive end-crushing.

The exploiting synthetic composites in crash worthiness applications due to its properties to withstand the applied load,higher specific strength and stiffness,corrosion resistance and the ability to tailor.Despite the failures of constituents in the synthetic composite are brittle in nature but the interest currently in most of the composite material application is the new combination of high efficiency materials for crash worthiness[69,83,124].Therefore,a numerous amount of crashworthystudy,experiments,and computer simulations is conducted crushing outcome and evaluate the crushing behavior.For example,Lu et al.[145]study was introduced different configurations of foam and wall thickness gradients of thin-walled structure,which resulted graded foam material and tube wall thickness have shown the certain benefit of theSEAvalues.

Extensive volumes of energy are absorbed in both progressive folding and progressive crushing are displayed in Fig.9(a),(b)and(c)which has described the combination of collapse behavior of hybrid energy absorption tube.The study by Othman et al.[31],R.Kalhor,S.W.Case[144],and Guohua et al.[85]have shown in the deformation pattern of hybrid tube which consists multiple crash worthiness behavior in combination of collapse modes.Thus,the example of collapse mode of hybrid tube component from metal and PMC fibre shown the collapse of hybrid tube are more stable compare to the other single component material(homogeneous/anistropic),therefore in the Fig.9 also depicted the crushing of hybrid tube are rigid at final crushing condition,which the crushing tube are intact whereas of each component in the collapse tube are contribute into collapse mode within their own collapse mode behavior capability[18].Therefore,the strength and energy absorbed are higher when compare into single component material but crushing integrity of hybrid tube from Fig.9 showed that the hybrid tube at final stage are rigid and justify the main function of energy absorption tube as sacrificial structure where the energy absorption tube are literally shown the ability in crushing integrity to minimize the impact forces.

5.2.Progressive folding

A brief explanation by Hull[24]of the progressive folding is illustrated in Fig.10(a),where it describes the main features of the progressive folding mechanism that exists in three-phase regions in the load-displacement curve.The model of progressive folding in Fig.10(b)by Guohua et al.failure modes and energy absorption of the braided composite tubes are influenced by the fibre types and their hybrid kind and the indicated three different crush failure modes occurring in the[85]resembles the mode observed in ductile metal tubes,which reflect to the Fig.10(a)progressive folding curve.Thus,in the study by Chin,Tsai,and Huang[146]have observed that the crush crushing process experiment,which are splaying mode for tubes with carbon braiding yarn,a folding mode for tubes with Kevlar braiding yarn,and a spiral-curling mode for tubes with both carbon and Kevlar braiding yarns.And from the results,it indicated that the folding mode is the lowest crush energy absorbed compared with other two modes.

Meanwhile,the study by Zhu et al.[85]on the crushing characteristics of hybrid aluminum/CFRP which was compared with empty aluminum tube and CFRP tube to explores similar configurations energy absorption and damage behaviors of the tube under quasi-static axial loading(Fig.10 and Fig.11).A study by Thornton and Edwards[147]of collapse mechanism to a variety of synthetic composites tubes from glass,graphite,and Kevlar fibre composites.From the results and data Thornton and Edwards[147]have concluded that the fracture collapse mechanism is complex despite the folding collapse mechanism is more stable upon the thin walled tube and the tube retains intact at the final stage of crushing(Fig.10(b)).

5.3.Progressive crushing

Naturally,the FRP composite tubes are experienced the several types of crushing mechanism,moreover in hybrid composition tube the collapse behavior will associated with circumferential of lamina bending, fibres fracture,delamination,and axial cracking in static or dynamic compression loads.Many aspects can dominate the failure modes in progressive crushing characteristics such as the thickness of the tubes,material properties,tube geometry,as well as techniques of fabrication and fibre orientation.The progressive crushing consists of the formation of a region of microfracture at one side of the tube which then propagates along the tube.Considerable volumes of energy are absorbed in both progressive folding and progressive crushing.However,more energy is usually absorbed in progressive crushing[134,147].

In Fig.11 Hull[24]have illustrated the main features in the normal progressive crushing process of the chamfering of PMC tube.Fig.11(b)has described the sequence of events where it reflects to the schematic load-displacement curve in Fig.5.From the real crushing condition study by Guohua et al.it was shown the tube partially crushed and at the final stage of crushing the debris are accumulating at the bottom of the tube and compacting to prevent further crushing.Refer to the Fig.10(a),the crushing process occurs at the top of the tube with initial slope due to chamfer mechanism and reaches pointPmaxand sudden drop,which call relaxation process and followed by the formation of non-linear fluctuation,which called the progressive crushing behaviour along at displacement Si.While the constant load occurs at crush zone and the fluctuated until the displacement reaches the final displacement,and the load increases rapidly due to compacting of debris and eventually block the process of crushing and it was also indicate the end of progressive crushing.

The study of Kim,Yoon,and Shin[121]have focused on the failure modes and energy absorption capabilities of different kinds of circular tubes FRPs(carbon,Kevlar,and carbon/Kevlar FRP)has found that the specific energy absorption of the tubes with the brittle fracture mode revealed the strongest relationship with the compressive strength.Meanwhile,the variety of geometrical designs and triggering effect which goes with failure modes of FRP tube as energy absorber tube have been studied by Lau,Said,and Yaakob[107]and Rabiee and Ghasemnejad[141]have mentioned the most of anisotropic materials are tailor ability,where these factors of tailor ability is an advance where the structure can be modified in certain design which allows for enhancing the peak load and specific energy absorption significantly according to the application.Meanwhile,Bisagni et al.[3]have described the numerical study of energy absorbers for Formula One side impact and steering column impact using finite element model LS-DYNA which are comparing the numerical data with experimental results has found that the total differences of progressive collapse energy absorption are around 10%.

6.Application

Back to couple decades ago,a few composite materials already introduce since 1908,such as melamine and glass fibre,which the first composite materials were linked for the manufacture of extensive amounts of applications and daily life application gadget and advanced military equipment's.Meanwhile,efficiency of a material in load bearing application such as energy absorption tube in composites fibres are considered as replacements for metallic materials.For example,a composite energy absorption tube has been used in the sandwich panel as the core,aircraft landing gear as energy absorption tube and several parts in motorsport as a monocoque in Formula One.Meanwhile,hybrid composite materials into energy absorption tube or crash box have it possible to be utilized and designed for a particular type of load into the various major structure for high-performance application and safety equipment in major transportation industries such as aerospace,automotive and marine industry(Fig.12,Fig.13)[2,9,10].It also offers a number of advantages over conventional synthetic composite materials,such as resistance to chemicals and thermal and electrical insulation properties and product sustainability.

7.Summary

This paper reviewed the development of hybrid energy absorption tube application in approach of anistrophic and homogeneous material.Normally,the energy absorbing tubes have been designed in any types of FRP composite because of it canprovide an excellent collapse behavior and possess good load carrying ratio when compared to metallic material.Therefore,the previous results of the hybrid energy absorption tube study have shown that the hybridization effect in composite energy absorption tube could be an effective way to enhance the energy absorption capacity and response of such tubes applications into crash worthiness is significant to compare to other homogeneous materials in the previous study.Besides,in this paper,the exploration into a new design concept and technique of fabrication from varies of research study also have brought together and extended the knowledge of crash worthiness in energy absorption tube as a safety device.Moreover,the concept hybridization in composite fibre materials into technique fabrication have considerably more controllable if adequate attention into various parameters and matrix constituents,plus it also improvised the mechanical properties and collapse characteristic other than heterogeneous material as energy absorption tube application.Likewise,the effect of hybridization in composite tubes exhibited a more desirable according to type failure mode,therefore they are considered to be more suitable candidates as energy absorbing structural members in service conditions.Furthermore,the incorporation of different natural fibre polymers with synthetic fibres which can lead to enhance the applications of natural fibres and supersede the non-biodegradable materials in the field of engineering and technology.

Therefore,in the recent experimental study of hybrid composite on energy absorption application shows the capability of renewable and biodegradable(Biocomposite)composite materials corresponding to high-performance energy absorption tube into various safety devices products.Therefore,many of hybrid energy absorption tube study apply the combination of materials such as synthetic-synthetic fibre composite polymer[148],synthetic fibre metallic composite polymer,nature fibre-metallic composite polymer[149],and nature fibre-concrete composite polymer[150],meanwhile,a hybrid composite from nature-synthetic fibre composite polymer is less study in energy absorption application.Furthermore,composite of glass fibre and natural fibres,such as flax,hemp,kenaf,and jute,are gaining increasing reputation in automotive,aerospace,container and many other industrial applications.Plus,with the market scenario of composite applications is changing due to the price are sky-rocketing of synthetic composite and environmental issue,thus the introduction of newer biodegradable fibres or hybridization is the one solution into contributing sustainability of the application in the composite and able to determine the qualitative effect and providing an insight in to the general response which has not focuses only inpreliminary design.

Acknowledgement

The authors would like to show appreciation to Universiti Putra Malaysia for financial support via the Graduate Research Fellowship(GRF)scholarship through the School of Graduate Study(UPM/SPS/GS47054)for providing a scholarship to the principal author to carry out this research project and HiCOE grant(6369107)from Ministry of Higher Education Malaysia.