Application of stiffness geometries in the lightweight design and optimization of automotive monolithic deep-drawn hard-shell rooftops

Hard-shell rooftops are camping accessories that are mounted on top of vehicle roofs for quick, convenient, and comfortable shelter during outdoor activities such as camping and overlanding. The designs that are currently available in the market rely on multi-part (polylithic) structures that are manufactured separately and joined using mechanical fasteners (bolts, nuts, rivets), adhesives, or welding. This leads to design, manufacturing process and quality limitations such as excessive weight as reported by customers, a high number of individual parts, multiple process operations, a risk of leakage at joints requiring rework, long production times, and increased operational costs. These challenges motivate the need for a lightweight, monolithic and manufacturable alternative. This research investigated the application of stiffness geometries, that is, the strategic geometric features that enhance structural rigidity without adding weight, in the lightweight design and optimization of an automotive monolithic (one piece) deep-drawn hard-shell rooftop. A monolithic design framework was developed to integrate geometric design, material selection, parametric optimization, numerical simulation and manufacturing feasibility within a unified approach. The monolithic hard-shell rooftop CAD model was developed alongside a decision support system that guided the material selection process. The stiffness geometries were parameterised in terms of length (L), width (W), and height (H), and were optimized to maximize stiffness subject to geometric, spacing, manufacturing, and material properties and material thickness constraints. The optimized design was evaluated for stiffness through Finite Element Analysis (FEA) and for deep drawing feasibility simulations. The prototype was manufactured using the deep drawing process. The deep-drawn prototype was experimentally tested for material distribution and stiffness. Material distribution was uniform and closely matched the simulation results, with a difference of < 1% for thickness and 3.74% stiffness. Compared to the existing polylithic design, the monolithic hard-shell rooftop achieved substantial improvements. Stiffness per unit weight was increased from 2.25∗105 𝑚−1 to 3.26∗105 𝑚−1. Part count was reduced from twenty-three (23) single parts (polylithic) to one (1) part (monolithic). Weight was reduced by 30%, process routes were reduced from eight (8) to three (3), production time was reduced by 120 mins, and leaking was eliminated. The original contributions of this research include the demonstration, for the first time, that an aluminium hard-shell rooftop can be fully monolithic, deep-drawn from a single sheet, with integrated stiffness geometries, and validated for structural integrity and manufacturability. Additionally, a new methodology was developed for determining the optimum stiffness parameters for the monolithic hard-shell rooftop. The stiffness geometries were parameterised in terms of length (L), width (W), and height (H), and were optimized to maximize stiffness subject to geometric, spacing, manufacturing, and material properties and material thickness constraints. This research also introduced a novel and holistic framework that integrates monolithic design, material selection, stiffness geometry optimization, and deep drawing feasibility simulations into a single decision-making framework. The research further contributed a validated methodology for reducing weight, part count, manufacturing operations, production time, and eliminating leakage risk in aluminium hard-shell rooftops through monolithic design. Finally, a web-based, scalable, automated, and data-driven material selection decision support system was developed and tailored to the unique requirements of hard-shell rooftop design and manufacturing.

Grantor dc:publisher

Stellenbosch : Stellenbosch University

Year dc:date.issued

2026

Author dc:creator

• Chirinda, Gibson Pasbel

Advisors dc:contributor.advisor

• Matope, Stephen
• Sterzing, Andreas

Language dc:language.iso

en

Repository record dc:identifier.uri

https://scholar.sun.ac.za/handle/10019.1/135686

OAI identifier oai:identifier

oai:scholar.sun.ac.za:10019.1/135686