Analysis of conventional and composite leaf spring using ANSYS

In the present scenario, strength of the structures has been the main focus of automobile manufacturers. The suspension leaf spring is one of the potential items for higher strength in automobiles as it accounts more than two times stronger than the conventional steel leaf spring. This helps in achieving more damping capacity, less fuel consumption and resistance against impact loads in the vehicle. The introduction of composite materials made it possible to avoid catastrophic damage due to sudden impact loads that are transferred to the chassis of light passenger vehicle through the leaf spring. In this work, an attempt has been made in replacing the design of a conventional multileaf leaf spring by a composite multileaf leaf spring based on strength ratio without any modification of the existing design of a light passenger vehicle. The materials adopted in the analysis of composite multileaf leaf spring are glass/epoxy, glass jute /epoxy, carbon jute/epoxy. The optimum material combination is determined based on the maximum induced bending stress, material availability and the contact pressure generated between each and every laminate which will influence the unsprung weight of the light passenger vehicle. Due to impact loads acting on the multileaf leaf spring damage tolerance work is also carried out in the composite material that has minimum contact pressure by creating artificial hemispherical damage for varying proportions. The optimum composite multileaf leaf spring is fabricated using filament winding technique. Modeling and contact analysis were carried out for both conventional and composite materials using ANSYS 8.1 software. From the investigations undergone, it is well proved that composite multileaf leaf spring made of glass/epoxy is found to be of higher strength comparing strength ratio, induced bending stress, contact pressure as well as with respect to cost, than the conventional leaf spring and the optimum damage radius due to sudden impact loads is also predicted in the composite multileaf leaf spring.

Design and analysis of composite mono leaf spring for passenger cars

Conventional materials used for an automotive suspension system are one of the key parameters which influence the vehicle weight. Hence the use of composite material for suspension system would offer a significant benefit of being light in weight also have a high life span compared to existing materials, without compromising the load-carrying capacity and stiffness. The primary emphasis of this paper is on gaining a finite element-based performance analysis of advanced composite materials as a substitute for conventional materials used for the application of leaf spring suspension of an automobile. The leaf springs were modeled using CATIA, to replace the existing material of steel alloy and carbon alloy leaf springs with a composite material (Carbon Fiber-reinforced polymer) for a pickup truck and Finite Element Analysis (FEA) was performed using ANSYS for static load condition and the results were compared with conventional leaf spring materials to determine the structural characteristics. Furthermore, vibrational characteristics were also presented by modal analysis for the designed leaf springs. It was inferred from the results that advanced composite materials are light in weight, optimal, and ideal material for the leaf spring offering better structural & mechanical behavior.KeywordsANSYSCATIAComposite materialsFinite Element AnalysisLeaf springsNatural frequencyStatic analysis

This paper presents an approach for the design optimisation of suspension springs, such as coil springs, torsion bar springs, steel leaf springs and composite leaf springs, using a Simulated Annealing algorithm. Around 14.39% of coil spring mass and 7.12% of torsion bar spring mass are reduced. In the case of steel leaf springs, 14.40% of mass, under two variables condition and 16.58% of mass, under three variables condition are reduced. Similarly, 22.93% of mass under two variables condition and 29.28% of mass under three variables condition are reduced in the optimisation process of composite leaf springs. When the composite leaf spring is compared with the conventional steel leaf spring, the mass reduction obtained before optimisation is 83.52% and mass reduction obtained after optimisation is 85.16% in the case of two variables condition and 86.03% in the case of three variables condition for the same load carrying capacity and stiffness.

Characterization and Investigation of Mechanical Properties of Composite Materials used for Leaf Spring

Composite leaf springs with variable stiffness function (‘shape memory alloy (SMA) hybrid composite leaf springs’) were constructed by embedding three-dimensional SMA actuators into a multi-material composite system. Bench test of dynamic stiffness and fatigue characteristics revealed that epoxy resin matrix leaf springs exhibit the highest initial strength/stiffness but suffer rapid long-term decay due to brittle fracture and Joule thermal softening. Although SMA phase transformation enables temporary crack closure, the interplay between thermal damage and cyclic repair restricts durability. Thermoplastic polyimide (TPI) matrices exhibited outstanding fatigue resistance under actuation, attributed to superior thermal stability and molecular chain reconstruction, while SMA activation effectively inhibited crack propagation. Polydimethylsiloxane (PDMS) matrix leaf springs are suitable for long-term active control scenarios due to hyperelastic interfacial slip and modulus mismatch. However, while the short-term increase in stiffness and strength after energization is high, interfacial delamination triggers catastrophic failure after 5000 cycles, making PDMS matrix leaf springs suitable for short-term deformation requirements only. The TPI-SMA synergistic architecture provides a theoretical foundation for resolving the intrinsic trade-off between active stiffness tunability and fatigue resistance, thereby demonstrating the substantial potential of intelligent structural composites for advanced automotive applications.

Design, analysis and optimization of a composite leaf spring for light vehicles

Suspension behaviour of kenaf and hemp fibre composites leaf spring using finite element analysis

Composite leaf springs constructed of glass fiber reinforced polymeric materials have been recognized as viable replacements for steel springs. Experience gained in the use of composite leaf springs in passenger vehicles is encouraging and clearly demonstrates the utility of glass fiber reinforced composites for leaf spring applications. This paper dis cusses a study on the use of glass fiber reinforced composite leaf springs for commercial vehicles, particularly for heavy tank trailer suspension systems. A general discussion on the analysis and design of constant width, variable thickness composite springs is pre sented. An example is given for the design of a composite spring for one of a tank trailer fleet. This spring is three inches wide with a maximum thickness of about two inches. Several dozen springs were fabricated according to the design and road tested on tank trailers. In general, the road test results demonstrated the applicability of glass fiber rein forced composite springs for trailer suspensions. The composite leaf springs were well received by the trailer operators.

In this report, we will describe a magnetic-spring-type balancer utilizing an effect of a magnetic spring in place of a balancer using either a conventional leaf spring or bar spring. A quite low spring constant can be easily realized by a magnetic spring utilizing a pair of permanent magnets and a steel ball. In addition, there is no vibration mode of higher degree as found in the leaf spring of the bar spring, and a stable measurement can be performed even if the number of revolutions is increased. We have applied this magnetic-spring-type balancer to a VTR cylinder and obtained a measurement accuracy of less than ±5% and a minimum resolution of 2×10 kg-m.

The Automobile Industry has shown increase interest for replacement of steel leaf spring with that of composite leaf spring. Substituting composite materials for conventional metallic materials has many advantages because of higher specific stiffness, strength and fatigue resistance etc. This work deals with the replacement of conventional steel leaf spring with a hybrid Composite leaf spring using E -Glass/Carbon/Graphite/Epoxy. The hybrid composite is obtained by introducing more than one fiber in the reinforcement phase. The hybrid composite is fabricated by the vacuum bag technique. The result shows that introduction of carbon and graphite fiber in the reinforcement phase increases the stiffness of the composite.

Suspension systems are automotive parts whichabsorb sudden impacts caused by roads and providing comfort have an essentialrole in the automotive sector. Reducing weight is a fundamental way to decreaseenergy consumption and emission release. This study establishes improvementconditions by analysing layered composite springs which have differentcompositions and different support angles under various weights. Ten plaqueswhich made with various compositions chitosan and carbon nanotubes, alsoone-way glass fiber/epoxy composite plaques with prepreg method and oneunalloyed plaque were produced. Standard samples were extracted by water jetand pull&push test were applied to identify mechanical properties. Fivestandard samples were used to identify each mechanical property. Mechanicalproperties of samples with different compositions were compared.Identified mechanical properties were used asmaterial properties at the ANSYS ACP PRE&POST analysis program. Compositespring thicknes were 12 mm and it is composed of 60 layers. Static analysis ofcomposite springs modelled with five different layer orders was done byapplying 1000 N, 2000 N, 3000 N and 3750 N force. Collapse, stress and shapechanges of composite springs were examined at static analyses.Analysis show that unalloyed composite leafspring is more resistant than its counterparts. When Layer Order 1 (TD1) [0°)]60 with the same direction for fiber and horizontal axis of composite leafspring is compared with others, it is seen that composite spring with TD1 ismore rigid against bending. Damage analysis was done with ACP POST programaccording to Tsai-Wu and Hashin standards and it is seen that end points ofsprings were mostly damaged. Most damaged one is the TD5 leaf spring with [(0°5/90°5/45°10/-45°10)]slayer order under 3750 N according to Tsai-Wu standard. In addition tothat, composite leaf springs were %49,84 lighter than mostly used one leafsteel counterparts.

In this study, a statistical approach was developed to predict fatigue failure of laminated composite leaf springs prepared with carbon nanotube (CNT) filled epoxy/woven glass fibers. Electrical resistance change method and the Weibull analysis were adopted to develop a statistical approach. The electrical conductivity for successful application of health monitoring of leaf springs was achieved by dispersing 0.4 wt% of CNTs into epoxy resin. In‐situ monitoring of damage in composite leaf springs during fatigue tests applied as cyclic flexural deflection was carried out at nine different displacement ratios. The critical fatigue cycle and the corresponding change in electrical resistance were determined at each displacement ratio. Then, the critical electrical resistance change to cyclic fatigue was found 0.15% with 95% reliability by the Weibull analysis. The average fatigue life and the average strength loss corresponding to the 0.15% resistance change ratio were found to be 48.33% and 9.88%, respectively. The reported statistical concept based on the monitoring of change in electrical resistance during deflection can be successfully employed as a useful tool to predict safety limits of composite structures subjected to fatigue loading, especially in aerospace industry.

Composite leaf springs represent a key application of composite materials in the field of automotive lightweight materials. Stiffness, as a critical parameter of composite leaf springs, is closely related to the handling stability and ride comfort of automobiles. Therefore, this paper proposes an explicit theoretical model, which can consider the anisotropy of composite materials and detailed structure of the leaf spring, to predict the stiffness based on the law of energy conservation. The obtained results are verified against the results of the finite element method and bench test of basalt/epoxy samples. Moreover, the influence of the relevant design parameters on the stiffness is analyzed to provide guidance for the stiffness matching of composite leaf springs. The thickness of the composite leaf spring considerably influences its stiffness. As a key parameter representing the bearing capacity, the strength is closely related to the reliability of leaf springs. Based on the Tasi-Wu strength failure criterion, the influence of the relevant design parameters on the strength ratio of a composite leaf spring is analyzed under the constraint of stiffness. An increase in the width of the composite leaf spring enhances its bearing capacity when the stiffness is required to be within a certain range.

The present work investigates the fatigue performance of fibre-reinforced injection-moulded leaf springs. Twenty per cent discontinuous long, short glass fibre-reinforced polypropylene (SFPP) and unreinforced polypropylene (UFPP) materials are used for manufacturing constant-thickness, varying-width, mono leaf spring. Fatigue tests are performed on moulded leaf springs at various alternating loads under the pulsating compression mode at 0.5Hz frequency with the aid of in-house developed fixtures integrated with the servo-hydraulic fatigue machine. During fatigue testing, cyclic load—deflection of the test leaf spring of each and every cycle is measured; the energy dissipation ratio and spring rate of the test leaf springs are reported as an index for the accumulated damage at various stages of its life. Test leaf springs are subjected to fatigue load up to 2×105 cycles or failure, whichever is earlier. SFPP and UFPP leaf springs exhibited drops in the spring rate, whereas long glass fibre-reinforced polypropylene exhibited fracture as leaf spring failure. Fatigue performance as well as failure morphology of the leaf springs confirmed the role of reinforced fibre length in the thermoplastic composite leaf spring.