Plastic Tailgate Reinforcement for Impact Integrity
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Solution Overview
Problem
Current plastic material-based motor vehicle tailgates fail to simultaneously meet the requirements of not separating from the vehicle, remaining intact as a single entity, and continuing to block the opening during high-speed impacts, due to limitations in mechanical reinforcement materials like textiles and cables which lack sufficient rigidity.
Innovation Solution
A motor vehicle sub-assembly comprising a thermoplastic material with a Young's modulus between 500 MPa and 3000 MPa and a coefficient of elongation at break greater than 20%, specifically designed for the internal structure with mechanical reinforcements in identified rupture zones, ensuring the integrity and rigidity of the tailgate during impacts.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If a complementary part made of steel is used to hold together broken pieces, then the pieces are held together, but the cost and weight become incompatible with the interest of using plastic material
Solution Approach 1:
The patent changes the material parameters by using a thermoplastic reinforcement instead of steel, accepting lower strength properties in exchange for weight reduction. The reinforcement has specific mechanical properties (Young's modulus between 500-3000 MPa, elongation at break greater than 20%) that are optimized for the application.
Solution Approach 2:
The patent creates a composite structure by combining the plastic material of the opening panel with a thermoplastic reinforcement. This composite approach allows the reinforcement to provide structural support while maintaining compatibility with the plastic matrix, achieving both weight reduction and adequate strength.
2Strength
If a woven textile reinforcement is used to hold together broken pieces, then the pieces are held together, but the assembly lacks sufficient rigidity to block the opening during high-speed impact
Solution Approach 1:
The patent changes the material parameters by selecting a thermoplastic reinforcement with specific mechanical properties: Young's modulus between 500-3000 MPa (higher than textile) and elongation at break greater than 20%. This parameter optimization provides both holding strength and sufficient rigidity to maintain blocking function during impact.
3Strength
If rigid plastic materials are used for the inner box to guarantee geometrical strength during normal use, then the geometrical strength is guaranteed, but the material stretches very little in case of high-speed impact
Solution Approach 1:
The patent creates a composite structure combining the rigid plastic inner box with a thermoplastic reinforcement. The rigid plastic provides geometrical strength for normal use, while the thermoplastic reinforcement (with elongation at break greater than 20%) provides ductility and stretching capability during high-speed impact, allowing the assembly to absorb impact energy.
4Strength
If cables or reinforcement fibre braids with play are used to hold together broken pieces, then the pieces do not fall onto the road, but the pieces remain separated by 5 to 10 cm and are almost free due to flexibility
Solution Approach 1:
The patent changes the material parameters by using a thermoplastic reinforcement with Young's modulus between 500-3000 MPa and elongation at break greater than 20%. This provides sufficient rigidity to minimize separation distance between broken pieces while maintaining adequate holding strength, eliminating the 5-10 cm separation gap that occurs with flexible cables and braids.
Data Source
AI summary
Motor vehicle sub-assembly (10) comprising a first part (20) made of plastic material forming an outer bodywork skin, and a second part (30) made of plastic material forming an internal structure to which said first part (20) is attached, characterised in that the second part (30) comprises at least one mechanical reinforcement (40) made of thermoplastic material having a Young's modulus less than that of the plastic material of the second part (30), and a coefficient of elongation at break greater than that of the plastic material of the second part (30).