It’s one month until industry, academia, government and regulatory bodies and standards organizations gather at the Suburban Collection Showplace in Novi, Michigan, for Automotive Testing Expo North America 2025 (October 21, 22, 23) to accelerate innovation and form new strategic partnerships in fast-evolving areas such as EV production.
During The Future of Automotive Testing Conference on October 22, Prasad Kulkarni, manager of body structures engineering at Mahindra North America, will contribute to the critical dialogue on EV safety and its evolving testing landscape through his presentation, ‘Engineering and testing safer EV structures: the next frontier in body-in-white design’.
ATTI spoke with Kulkarni to find out how Mahindra approaches engineering safety through advanced testing methodologies – from high-fidelity CAE simulations to rigorous physical validation.
How does body-in-white (BIW) design underpin crash energy management, stiffness, weight efficiency and compliance with evolving global safety standards?
As an experienced automotive structural engineer, I see the BIW as the foundation of a vehicle’s performance. It’s the primary load-bearing structure that enables all core functions.
BIW design is the cornerstone of crash energy management. Through meticulous CAE, we strategically design load paths and crumple zones (typically in the front and rear) to deform in a predictable, controlled manner, absorbing kinetic energy before it reaches the occupant cell. Conversely, the passenger safety cage is engineered for maximum rigidity, utilizing high-strength steel (HSS), press-hardened steel (PHS) and, increasingly, aluminum and carbon-fiber composites to preserve survival space. This same structural integrity directly translates to global stiffness (torsional and bending), which is critical for vehicle dynamics, handling precision, refinement (NVH) and the effective deployment of ADAS that rely on precise sensor alignment.
We achieve weight efficiency using a systems engineering approach. This involves optimizing geometries, using multimaterial strategies and employing advanced joining techniques like flow-drill screws and structural adhesives.
Finally, compliance with global safety standards – from Euro NCAP and China’s C-NCAP to the US IIHS small overlap protocol – is integrated into the BIW’s architecture from the start. We are now designing BIW structures that are safe for occupants and pedestrians, including features like active hoods, while also addressing the unique safety requirements of electric vehicle battery packs.
Why does BIW matter in EVs?
The BIW is the single most critical system for holistic crash safety, as its purpose expands beyond protecting occupants to also safeguarding the high-voltage battery system, which can fail in unique and severe ways.
The BIW forms an essential protective fortress around the battery pack. In a side collision, for example, the BIW’s rocker sections and crossmembers must be engineered to prevent intrusion far more aggressively than in an ICE vehicle. A breach could lead to a catastrophic short-circuit, thermal runaway and fire.
The immense weight of the battery pack also drastically changes crash dynamics. The BIW must manage this added mass and prevent excessive deceleration from reaching the occupants. The structure itself is different; the rigid battery pack is often integrated as a stressed member, which significantly boosts overall torsional stiffness. This requires new design approaches, such as aluminum casting nodes, which reduce part count and create more predictable load paths.
The BIW must manage crash energy without compromising the battery’s integrity. This often means creating strengthened load paths around the pack using ultra-high-strength steel crossmembers to absorb impact. The structure must also provide secure, protected mounting for all other high-voltage components, preventing post-crash electrical hazards, coolant leaks or fires. In short, the EV BIW is a holistic safety system whose design dictates the vehicle’s performance and its ability to meet the most stringent safety protocols.
How do you prevent battery intrusion?
Preventing battery pack intrusion is the top priority for an EV’s BIW in a crash. We achieve this with a multilayered defense strategy.
Reinforced side sills are the first line of defense in a side impact. They are now a combination of ultra-high-strength steel and aluminum extrusions, sometimes filled with structural foam. This creates a massive, strong barrier against pole or barrier impacts.
Staged crush zones in the front and rear are calibrated through CAE to collapse in a specific sequence. This managed deformation absorbs the majority of the crash energy before forces can propagate inward toward the rigid safety cell and the battery.
Finally, seamless load paths are continuous networks of high-strength materials that channel these immense forces around the battery compartment, diverting them into the rockers, A-pillars and floor crossmembers. The synergy of these three elements ensures that crash loads are managed and dissipated by the BIW structure itself, leaving the battery pack isolated and intact.
How do crash regulations across the US, Europe and Asia drive BIW design choices and compliance challenges?
Navigating the global regulatory landscape is one of the most complex aspects of BIW design. It often requires a ‘design-for-all’ approach that incorporates the strictest requirements from each region.
The US (IIHS and NHTSA) drives innovation with extreme test protocols like the small overlap frontal test. These tests require robust lateral load paths at the outermost edges of the vehicle’s front end, which directly influences the design of the front rails and A-pillars. FMVSS 305 also specifically mandates electrical system integrity after an EV crash.
Europe (Euro NCAP) focuses on occupant and pedestrian safety. Its emphasis on side-impact protection, including far-side impact, drives the reinforcement of B-pillars, door structures and center consoles. Its strict pedestrian protection protocols also influence the design of the front end and the integration of active hood systems.
Asia, including India’s Bharat-NCAP and China’s C-NCAP, often adopts and sometimes anticipates European protocols. It also adds unique elements like whiplash testing and rigorous EV-specific safety checks. The challenge is that a BIW designed for one region may not perform well in another. Therefore, the industry trend is to design a global BIW platform that is over-engineered to meet the highest standards of all these regions. This adds complexity and mass, making weight efficiency even more critical to achieve.
How do you balance strength and weight?
The modern EV BIW is a masterclass in multimaterial design, where we use the right material in the right place with the right joining technology to optimize strength, weight and safety.
Advanced high-strength steel (AHSS/UHSS/PHS) remains the workhorse for the passenger safety cage and critical impact zones. The latest generations, such as press-hardened steel (PHS) with strengths up to 2,000MPa, are essential for A- and B-pillars and roof rails – areas where maximum strength and minimal deformation are required. Their high strength-to-weight ratio and low cost make them ideal for protecting occupants and the battery in a side intrusion.
Aluminum alloys are favored for their excellent strength-to-weight ratio and are used in large, energy-absorbing components. High-pressure die-castings, like Tesla’s giga-castings, reduce the number of parts and create incredibly rigid nodes. Aluminum extrusions are perfect for crash management systems and battery enclosure sides, as their complex cross-sections can be designed for optimal energy absorption.
The hybrid structure is where the real engineering happens. We join these dissimilar materials using self-piercing rivets, flow drill screws and structural adhesives. This balance is achieved by using steel for the highest-strength components and aluminum for larger, stiffness-critical or crushable zones. This approach lowers the vehicle’s center of gravity and achieves the required stiffness and safety performance, ultimately extending range without sacrificing occupant protection.
Which BIW design trends are shaping the future of EV safety?
We are entering a new era of BIW design, driven by manufacturing and a proactive approach to safety.
Functional integration and giga-casting: The trend toward massive, single-piece castings for the front and rear is revolutionary. By reducing the number of components and joints, we create more predictable and robust load paths. This enhances torsional stiffness and improves crashworthiness by eliminating potential failure points.
The battery as a stressed member: We are moving beyond simply protecting the battery to fully integrating it into the vehicle’s structure. Technologies like cell-to-chassis (CTC) embed battery cells directly into a platform that becomes a fundamental stress-bearing element of the BIW. This eliminates redundant mass and significantly boosts overall rigidity.
AI-driven topology optimization: The design process itself is evolving. We now use AI and machine learning to run millions of simulations, creating organic, lightweight structures that meet all stiffness and safety targets with minimal material. This allows us to design structures that were previously impossible to conceive or manufacture.
Proactive safety integration: The future BIW will be a ‘smart structure.’ This involves designing mounting points for sensors that can detect an imminent crash (e.g. radar/lidar) and prepare the structure accordingly. Imagine a BIW that can tension seatbelts and adjust airbag deployment parameters milliseconds before impact, moving us from passive to predictive safety. This deep integration of active and passive safety systems is the ultimate frontier for vehicle safety.
Why did Mahindra Automotive North America choose to speak on this topic at The Future of Automotive Testing Conference?
We want to contribute to the critical dialogue on EV safety and its evolving testing landscape. By presenting our advanced testing methodologies – from high-fidelity CAE simulations to rigorous physical validation – we aim to showcase how a global OEM engineers safety from the ground up.
Ultimately, our presence here is a statement of intent. It signals that Mahindra is not just observing the global EV transition; we are actively shaping it with world-class engineered products. By sharing our insights, we aim to forge the partnerships necessary to successfully launch our next generation of global EVs.
Prasad Kulkarni is the manager of body structures at Mahindra Automotive North America, with over 25 years of experience in body-in-white (BIW) structural design. His expertise includes crashworthiness, lightweighting and advanced manufacturing for passenger and electric vehicles. He has led programs across the vehicle development cycle, supporting platforms aligned with Bharat NCAP, Euro NCAP and FMVSS standards, and has pioneered the use of hot-stamped steels, aluminum and AI-driven optimization in structural topology.
Hear from Kulkarni at 1:55pm during The Future of Automotive Testing Conference on October 22. Visit the Automotive Testing Expo North America website to find out more about this year’s event and to secure your attendance.
