Hybrid Plastic Metal Bonnet Panel Thermal Deformation Control
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Solution Overview
Problem
Existing motor vehicle bonnet manufacturing techniques face challenges in weight reduction and aesthetics due to the use of hybrid plastic-metal materials with different thermal expansion coefficients, leading to deformation and visible seams during high-temperature processes like cataphoresis and painting.
Innovation Solution
A motor vehicle body panel comprising a plastic frame and an aluminium alloy skin panel, where the frame features a teardrop-shaped connecting portion with a recess and a calibrated external sealant to mask the seam, allowing separate processing of components and preventing thermal expansion issues, while maintaining an aesthetically pleasing finish.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Weight of moving object
If a frame made of plastic material and an aluminium alloy skin panel are used to reduce weight, then the weight of the body panel is reduced, but the different coefficients of thermal expansion cause unwanted and uncontrollable deformation phenomena during high-temperature cataphoresis and painting processes
Solution Approach 1:
The patent applies preliminary action by performing the joining operation before the high-temperature cataphoresis and painting processes. The frame and skin panel are joined using mechanical interlocking and adhesive bonding in advance, so that during subsequent thermal processing, the already-joined structure maintains its integrity despite differential thermal expansion, thereby preventing shape deformation.
Solution Approach 2:
The patent employs composite materials by combining plastic frame material with aluminium alloy skin panel through a hybrid joining system that includes both mechanical interlocking features and adhesive bonding. This composite construction allows the dissimilar materials to be securely joined while accommodating their different thermal expansion characteristics during high-temperature processing.
2Strength
If adhesives are used to prevent relative movements between the frame and panel during crimping, then the structural integrity is improved, but the different expansions of the two materials deform the shape of the bonnet compared to the design stage
Solution Approach 1:
The patent applies preliminary action by performing the joining operation before the high-temperature cataphoresis and painting processes. The frame and skin panel are joined using mechanical interlocking and adhesive bonding in advance, so that during subsequent thermal processing, the already-joined structure maintains its integrity despite differential thermal expansion, thereby preventing shape deformation.
Solution Approach 2:
The patent employs parameter changes by carefully selecting and optimizing the adhesive properties and the mechanical interlocking geometry to accommodate the differential thermal expansion between plastic and aluminium materials. The joining system is designed with specific dimensional parameters that allow for controlled movement and stress distribution during thermal processing, maintaining both structural integrity and shape accuracy.
3Reliability
If a second adhesive is applied to cover the crimping region to improve adhesion and protect from corrosion, then the protective function is improved, but a visible and protruding seam is created along the peripheral edge of the bonnet
Solution Approach 1:
The patent applies the taking out principle by removing the need for a second adhesive layer that creates visible seams. Instead, the design extracts the sealing and protective functions to be achieved through properly positioned structural elements and a single adhesive application that does not create aesthetic defects, thereby eliminating the protruding seam problem while maintaining protection.
Solution Approach 2:
The patent employs color changes by ensuring that the adhesive used is color-matched to the skin panel or frame material, making the adhesive line invisible or imperceptible from the exterior. This allows the single adhesive layer to provide both protective function and aesthetic appearance without creating visible seams along the peripheral edge.
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 enables a lightweight, deformation-free bonnet with an aesthetically enhanced appearance by avoiding thermal expansion issues and concealing the seam, thus improving both functionality and appearance.
Implementation Method 1
a layer of adhesive (19) joining the tab (17) to the surface (8)
Implementation Method 2
The outer surface of the connecting portion (18) and the end edge of the tab (7) define between them a gap (22), which is filled by a sealant (23)
Data Source
Figure 1~2
AI summary
A motor vehicle body panel (1), and in particular a bonnet, has a supporting frame (2) which is made of plastic material, equipped with a perimetric tab (7) and fixed to a skin panel (3) made of metallic material; the skin panel (3) has a shoulder portion (16) and its own perimetric tab (17), which is folded onto the shoulder portion (16) and joined to the latter by means of a connecting portion (18); the perimetric tab (17) of the skin panel (3) is arranged between the shoulder portion (16) and the perimetric tab (7) of the supporting frame (2) and is glued to the latter; the skin panel (3) is subjected to cataphoresis and/or painting before being joined to the supporting frame (2).