Rocker Assembly with Pultruded Composite Insert
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Solution Overview
Problem
Current energy absorbing structures in vehicles, such as rocker assemblies and side sill structures, face challenges in minimizing intrusion into the passenger compartment and maximizing energy absorption during collisions while maintaining minimal weight and accommodating large battery packs, especially in side impacts where crush space is limited.
Innovation Solution
A rocker assembly featuring a reinforcement panel with an elongated bar made of polymer resin embedded with continuous fiber roving, divided into sub-cavities filled with structural expanded foam, providing localized strength and ductility, and designed to absorb impacts effectively.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If traditional metal rocker assemblies are used to absorb impact energy, then energy absorption capability is improved, but vehicle weight increases
Solution Approach 1:
The rocker assembly employs a composite structure consisting of a polymer resin matrix reinforced with continuous fiber roving (such as carbon, glass, or basalt fibers). This composite material provides high strength and energy absorption capability comparable to metal structures while significantly reducing the overall weight of the rocker assembly, directly resolving the contradiction between strength and weight.
Solution Approach 2:
The elongated bar is designed with non-uniform fiber distribution, concentrating reinforcement strands in specific areas where higher strength is needed for impact absorption, while other areas have reduced fiber content to minimize weight. This localized quality variation optimizes the strength-to-weight ratio by placing material only where structurally necessary.
2Strength
If crush zones are increased to absorb impact energy, then energy absorption is improved, but space available for battery packs decreases
Solution Approach 1:
The composite rocker assembly achieves superior energy absorption in a compact form factor due to the high specific strength and toughness of the fiber-reinforced polymer. The continuous fiber roving embedded in the polymer matrix allows the structure to absorb substantial impact energy through fiber pullout, matrix deformation, and delamination mechanisms, all within a smaller volume compared to traditional metal crush zones.
Solution Approach 2:
The invention changes the material parameters by using advanced composite materials with tailored mechanical properties. The polymer resin matrix provides ductility and energy absorption, while the continuous fiber reinforcement provides structural integrity and strength, enabling effective impact energy absorption in a compact design that preserves battery pack space.
3Weight of moving object
If rocker assembly weight is reduced to improve fuel economy, then fuel efficiency is improved, but collision safety may be compromised
Solution Approach 1:
The fiber-reinforced polymer composite material provides collision safety comparable to or exceeding traditional metal structures despite the weight reduction. The continuous fiber roving (carbon, glass, or basalt) embedded in the polymer matrix creates a high-strength structure that effectively absorbs impact energy and maintains structural integrity during collisions, ensuring safety standards are met while achieving weight reduction for improved fuel economy.
Solution Approach 2:
The reinforcement strands are strategically positioned within the elongated bar to provide localized strength enhancement in critical areas subjected to impact loads, while maintaining overall weight reduction. This targeted reinforcement ensures collision safety is maintained in key structural regions without adding unnecessary weight throughout the entire assembly.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The solution effectively distributes load along multiple paths during collisions, enhancing energy absorption and minimizing weight penalty, thus improving vehicle safety and compliance with safety standards without compromising space for battery packs.
Implementation Method 1
A structural expanded foam polymer composition having a density of between 0.2 g/cc to 0.9 g/cc may be used to fill the sub-cavities
Implementation Method 2
The elongated bar is formed of a polymer resin that includes reinforcement strands of continuous fiber roving that are embedded in the polymer resin
Data Source
AI summary
A rocker assembly includes a rocker reinforcement panel attached to a side inner panel to define a cavity and an elongated bar disposed within the cavity. The elongated bar is formed of a polymer resin that includes reinforcement strands of continuous fiber roving that are embedded in the polymer resin and extend along a full length of the bar. The elongated bar has a constant cross-section perpendicular to the length of the bar that may define at least one elongated opening. A method of making a rocker assembly includes pultruding a polymer resin and a continuous fiber roving to form a reinforced elongated bar that is assembled into a cavity defined between the rocker reinforcement panel and the side inner panel.