Composite Motor Vehicle Floor Resolving Peduncle Strength and Weight
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Solution Overview
Problem
Existing motor vehicle rear floors made of composite materials with reinforcing fibers and polymer resin are not strong enough to retain seat belt peduncles during vehicle impacts, requiring a heavy steel cradle for support, which increases vehicle weight.
Innovation Solution
A rear floor design featuring a hollow body created by linking two parts, one made of Sheet Molding Compound (SMC) and another produced via Resin Transfer Molding (RTM), providing enhanced rigidity and mechanical resistance to tensile forces without the need for a metal cradle, while allowing deformation to absorb energy in impacts.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If a steel cradle is added under the floor to retain the peduncle during impact, then the peduncle retention strength is improved, but the vehicle weight increases
Solution Approach 1:
The floor is constructed using composite materials (SMC and RTM) that provide high strength-to-weight ratio, enabling the structure to withstand impact forces without requiring additional steel reinforcement. The composite material composition allows achieving the required peduncle retention strength while maintaining lower vehicle weight.
Solution Approach 2:
The floor is divided into two distinct parts: a first part made of SMC and a second part made of RTM. This segmentation allows each part to be optimized for specific functions - the SMC part provides overall structural strength while the RTM part provides localized reinforcement at the peduncle attachment zone, eliminating the need for a separate steel cradle.
2Strength
If the floor is made rigid to withstand tensile forces from seat belt peduncle, then the peduncle retention capability is improved, but the floor's ability to absorb impact energy is reduced
Solution Approach 1:
The floor exhibits different mechanical properties in different zones: the central zone containing the peduncle attachment point is designed with high rigidity and tensile strength to retain the peduncle during impact, while the peripheral zones are designed with greater ductility to absorb impact energy through deformation. This local differentiation resolves the contradiction between needing rigidity for retention and ductility for energy absorption.
Solution Approach 2:
The use of composite materials (SMC and RTM) with carefully selected fiber orientations and resin matrices enables the floor to achieve both high tensile strength in critical areas and controlled deformability in non-critical areas. The composite structure allows simultaneous optimization of both retention strength and energy absorption capacity.
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 design reduces vehicle weight by eliminating the steel cradle while maintaining the ability to withstand high tensile forces and absorb energy during impacts, thus protecting rear passengers and preventing damage to critical systems like fuel systems.
Implementation Method 1
injecting under vacuum and under low pressure a liquid polymer resin into the mold so as to impregnate the fibrous preform. The fibrous preform thus impregnated with resin is then heated to cause the crosslinking of the resin
Data Source
Figure 1~2
Figure 3~5
AI summary
The invention relates to a floor (30) comprising a first part (32) consisting of a composite material comprising a mixture of at least reinforcing fibres and a polymer resin, such as a sheet moulding compound (SMC). According to the invention, the floor (30) comprises a second part (60) which is injection-moulded by a polymer resin in a fibrous preform (RTM), the first (32) and second (60) parts being shaped and interconnected in such a way as to form a hollow body. Preferably, said floor (30) is shaped in such a way as to hold at least one element (72) for holding inside equipment of the motor vehicle (10).