Composite Crashbox Assembly for Progressive Impact Energy Absorption
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Solution Overview
Problem
Existing metal energy-absorbing devices used in motor vehicles for frontal impacts are heavy and do not align with the trend of making vehicles lighter, as they are made of metal materials that are not compatible with the goal of increasing lightweight construction in the automotive industry.
Innovation Solution
An assembly comprising a bumper beam and energy-absorbing devices made of plastics material with composite inserts, featuring regions of mechanical weakness such as slots, which are filled with compatible plastics material, to absorb impact energy without peak force transmission, thereby reducing repair costs and maintaining vehicle integrity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If metal energy-absorbing devices are used, then impact energy absorption capability is improved, but vehicle weight increases
Solution Approach 1:
The patent employs composite materials consisting of a plastics matrix reinforced with glass fibers or carbon fibers. This composite structure provides high strength-to-weight ratio, enabling effective impact energy absorption while significantly reducing the weight compared to traditional metal energy-absorbing devices. The composite material is molded into the energy-absorbing device body with integrated reinforcing ribs that enhance structural strength during impact.
Solution Approach 2:
The patent changes the material parameters by transitioning from metal to composite materials, and further optimizes the energy absorption characteristics by introducing regions of mechanical weakness with specific geometric parameters. The reinforcing ribs are designed with specific thickness ratios (between 0.5mm and 2mm) and the regions of weakness have controlled dimensions to ensure predictable breakage patterns that absorb impact energy efficiently.
2Strength
If energy-absorbing devices deform during impact, then impact energy is absorbed, but force peaks occur that can damage the vehicle behind the bumper
Solution Approach 1:
The energy-absorbing device is segmented into multiple regions of mechanical weakness distributed throughout its structure. These regions are designed to break sequentially during impact, dividing the force absorption into multiple stages rather than a single sudden deformation event. This segmentation prevents force peaks by creating a progressive collapse mechanism where each broken region absorbs a portion of the impact energy.
Solution Approach 2:
The regions of mechanical weakness are pre-designed and positioned in advance within the energy-absorbing device structure. These predetermined weak points are strategically located to ensure they break in a specific sequence during impact, cushioning the force transmission to the vehicle structure behind the bumper. The breaking of these regions occurs before the force can propagate to critical vehicle components, thereby protecting the vehicle.
3Force
If regions of mechanical weakness are added to the insert, then force peak is reduced, but device complexity increases
Solution Approach 1:
The regions of mechanical weakness are merged with the insert structure itself, eliminating the need for separate components. The weak regions are integrated directly into the molded composite insert, combining the functions of structural support and controlled breakage initiation into a single unified component. This integration reduces assembly complexity while maintaining the force peak reduction benefit.
Solution Approach 2:
The use of composite materials allows for the creation of regions of mechanical weakness through variations in fiber distribution, resin content, or local material composition rather than requiring separate mechanical features. The composite structure can be molded with varying densities and reinforcement patterns to create predetermined weak points, achieving force peak reduction through material heterogeneity rather than complex geometric features.
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 absorbs maximum impact energy during frontal collisions without damaging the vehicle behind the bumper, reducing repair costs and maintaining vehicle integrity while being compatible with lightweight vehicle designs without additional production costs.
Implementation Method 1
these energy-absorbing devices are made of a metal material due to their strength thereof... to absorb the maximum amount of impact energy throughout the impact
Implementation Method 2
at least one insert made of a composite material comprising a plastics material and a reinforcing filler embedded in this plastics material of the insert
Implementation Method 3
The insert preferably comprises a region of mechanical weakness that is arranged to promote initiation of the energy-absorbing device breaking... to avoid/reduce the force peak that could occur
Data Source
AI summary
The invention relates to an assembly (10) for absorbing impact energy, comprising a bumper beam and at least one energy absorbing device (1), interposed between this bumper beam (2) and a side member (3) of a motor vehicle, this energy absorbing device, also referred to as a crashbox, comprising a body comprising a plastic material and at least one insert (12) made from composite material comprising a plastic material and a reinforcing filler embedded in this plastic material of the insert, the plastic body and the composite insert being connected in particular by welding, bonding, thermoforming, the insert comprising a region of mechanical weakness (15) arranged to help initiate the breaking of the absorbing device.