Lightweight Design and Structural Analysis of Air Intake Manifold Using Composites

Abstract

This research presents a finite element analysis (FEA)-based investigation into the structural performance of an air intake manifold made from four different materials: Aluminum, Polyamide 6 (PA6), Polypropylene (PP), and Carbon Fiber Reinforced Polymer (CFRP). In response to the automotive industry\'s increasing demand for lightweight, fuel-efficient, and high-performance vehicles, the study explores alternative materials that can reduce component weight without compromising structural integrity. The air intake manifold was selected due to its significant impact on engine performance and efficiency. A 3D model of the manifold was developed using CATIA software and imported into ANSYS Workbench for simulation. Material properties were assigned, boundary conditions applied, and an internal pressure of 7 bar was used to simulate operating conditions. Fixed supports were applied at the mounting flanges. The analysis focused on key structural outputs: total deformation, equivalent (von Mises) stress, maximum principal stress, and factor of safety, allowing a comparative evaluation of each material\'s mechanical behavior. Results showed that Aluminium performed reliably with moderate deformation and adequate stress handling. PA6 exhibited slightly higher deformation but remained within acceptable limits, making it viable for medium-performance applications. PP, however, displayed excessive deformation and poor safety margins, suggesting its unsuitability for structural use. CFRP outperformed all other materials, demonstrating minimal deformation, low stress, and the highest safety factor, making it ideal for high-performance and weight-sensitive applications. This study confirms the utility of FEA in optimizing material selection during the early design stages of automotive components. It emphasizes the potential of composites like CFRP to meet modern performance and sustainability goals while offering insights for broader applications in lightweight vehicle design and advanced mechanical systems.

Introduction

The air intake manifold (AIM) is crucial in internal combustion engines for evenly distributing intake air, impacting combustion efficiency, emissions, and performance. Traditionally made from cast aluminum, AIMs are evolving towards lightweight composite materials like glass-fiber-reinforced polyamide (PA6) and carbon fiber reinforced polymer (CFRP) to reduce vehicle weight and improve thermal efficiency. Manufacturing methods include injection molding, resin transfer molding, and additive manufacturing.

AIMs are categorized as passive (fixed geometry, simple, cost-effective) or active (variable geometry controlled by the ECU for optimized performance across engine speeds). Active systems offer improved torque and power but are more complex; composites help mitigate weight concerns.

The manifold’s function starts with air intake, flowing through sensors, the plenum chamber, and runners, with active systems adjusting runner length to optimize engine output. AIMs also provide sealing, gas recirculation, fuel delivery, and airflow management, integrating components like EGR valves and injectors.

A literature review highlights the automotive industry’s shift towards lightweight materials for AIMs, emphasizing composite polymers’ advantages in strength, weight, and manufacturability. Key studies focus on vibration welding, noise and vibration performance, and dynamic behavior analysis of plastic manifolds, establishing testing standards and validating plastics like polyamide for automotive use.

The research methodology involves CAD modeling and finite element analysis (FEA) to optimize AIM designs using aluminum, PA6, polypropylene, and CFRP. Topology optimization created organic internal structures subject to load conditions. FEA assessed deformation, stress, strain, and safety factors under pressure. Analytical hand calculations verified simulation results. The study aims to identify materials and designs that balance lightweight construction with structural integrity for advanced composite or hybrid AIMs.

Conclusion

This research focused on the structural evaluation of an air intake manifold using a lightweight design approach with four different materials: Aluminium, Polyamide 6 (PA6), Polypropylene (PP), and Carbon Fiber Reinforced Polymer (CFRP). The main objective was to compare the structural behavior of these materials under identical operating conditions, using simulation-based finite element analysis (FEA) to determine their suitability for automotive applications. The manifold was first modeled in CATIA software to accurately reflect real-world geometry and then analyzed in ANSYS Workbench under standardized conditions, including a fixed support at the cylinder head flange and an internal pressure of 7 bar to simulate engine working conditions. The structural analysis used four critical evaluation metrics: total deformation, equivalent (von Mises) stress, maximum principal strain, and factor of safety. These parameters helped assess each material\'s stiffness, strength, and mechanical performance. The results revealed distinct performance characteristics for each material. Aluminium exhibited balanced performance with moderate deformation, low strain, and an adequate safety factor, making it a reliable and traditional choice with a good balance between weight and mechanical integrity. PA6 demonstrated higher deformation and strain compared to Aluminium but remained within acceptable limits. It was identified as a lightweight and cost-effective option suitable for medium-load applications, offering a good compromise between weight savings and mechanical performance. On the other hand, Polypropylene showed excessive deformation and low structural resistance, resulting in the lowest factor of safety. This suggests PP is not suitable for high-stress applications like intake manifolds in internal combustion engines, though it may be viable for non-structural, low-load components where cost reduction is prioritized. CFRP significantly outperformed all other materials, showing minimal deformation, very low stress and strain levels, and the highest factor of safety. This indicates its superior mechanical efficiency and validates it as the most suitable material for high-performance or weight-sensitive automotive applications. Despite its higher production costs and complex manufacturing requirements, the advantages offered by CFRP, particularly in racing or performance vehicles, justify its use where weight reduction and high strength are crucial. The study also highlighted the effectiveness of the Finite Element Method (FEM) as a simulation tool for evaluating the structural integrity of automotive components. FEM enabled detailed analysis through pre-processing (mesh generation and boundary condition setup), solution computation, and post-processing of results. It allowed for early detection of high-stress regions, design optimization, and rapid material comparison without the need for extensive physical prototyping. This virtual testing approach is especially valuable in accelerating the development process and reducing production costs. This study underscores the critical role of material selection in the structural design of automotive components. Aluminium remains dependable but heavier; PA6 offers moderate performance benefits; PP is limited to non-critical uses; and CFRP emerges as the most advanced material for future-ready, high-performance applications. With the support of robust simulation tools like FEM, lightweight and high-strength composite designs can be successfully developed to meet the evolving demands of the automotive industry.

References

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Copyright © 2025 Rajkumar ., Gyanendra Singh Yadav. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.