Fiber-Reinforced Resin Sheet Joining Incompatible Thermoplastics
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Solution Overview
Problem
Current methods for joining fiber-reinforced plastics (FRP) with thermoplastic resins face challenges such as high cost, weight increase, brittleness, and insufficient reliability due to stress concentration, especially when dealing with mutually incompatible thermoplastic resins, where existing techniques like mechanical joining and adhesive bonding are inadequate.
Innovation Solution
A fiber-reinforced resin sheet with a nonwoven fabric of reinforcing fibers impregnated with thermoplastic resin on one side, featuring a concave-convex interface layer with specific roughness and temperature compatibility, allowing for strong joining without adhesives or fasteners, enabling the integration of different thermoplastic resins through melt adhesion.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If mechanical joining using bolts, rivets, or screws is used to join FRP members, then the joining can be applied widely to different structures, but the cost increases due to processing at joint parts, the weight increases due to use of fasteners, and brittleness occurs due to stress concentration at processed parts
Solution Approach 1:
The patent replaces mechanical joining systems (bolts, rivets, screws) with a chemical bonding system using adhesives. The adhesive layer creates a continuous stress distribution across the joint area, eliminating stress concentration points and improving structural integrity while reducing weight and processing complexity.
Solution Approach 2:
The patent uses a composite joining system combining adhesive material with the FRP members themselves. The adhesive acts as a matrix material bonding the reinforcement members, creating a composite joint structure that distributes loads effectively and eliminates the need for separate mechanical fasteners.
2Strength
If adhesive joining is used to join FRP members, then the joining strength can be increased, but additional steps for coating adhesive are required and the reliability depends on the adhesive strength itself
Solution Approach 1:
The patent merges the adhesive coating process with the FRP manufacturing process itself. The adhesive is applied to the FRP members during the same production cycle, eliminating separate coating steps and reducing overall process complexity while maintaining reliable joint strength.
3Productivity
If melt joining is used to join thermoplastic resin FRP, then high-cycle joining at low cost is possible, but joining cannot be conducted between mutually incompatible thermoplastic resins and peeling occurs at the interface
Solution Approach 1:
The patent introduces an intermediate adhesive layer between incompatible thermoplastic resin FRP members. This adhesive layer acts as a mediator that is compatible with both thermoplastic resins, enabling reliable bonding at the interface while allowing the use of melt joining processes for high-cycle production.
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 the production of integrally molded articles with strong joining strength between thermoplastic resins, facilitating hybrid structures and improving productivity, suitable for various applications including automotive and electronic components.
Implementation Method 1
the thermoplastic resin (A) and the thermoplastic resin (B) form an interface layer having a concave-convex shape... enabling the integration of different thermoplastic resins through melt adhesion
Data Source
Figure 1~3(b)
Figure 4~5(b)
Figure 6~7
AI summary
A fiber-reinforced resin sheet and an integrally molded article are provided. The fiber-reinforced resin sheet comprises a nonwoven fabric made of reinforcing fibers having a thermoplastic resin (A) impregnated on one side of the nonwoven fabric. The fiber-reinforced resin sheet satisfies any one of the following conditions (I) and (II): (I) the nonwoven fabric has an area wherein the reinforcing fibers constituting the nonwoven fabric are exposed on the other side in the thickness direction of the nonwoven fabric, and (II) the nonwoven fabric has a thermoplastic resin (B) impregnated on the other side in thickness direction of the nonwoven fabric, and the nonwoven fabric has a reinforcing fiber volume ratio Vfm of up to 20% by volume, and wherein the thermoplastic resin (A) and the thermoplastic resin (B) form an interface layer in the sheet, and the interface layer has a concave-convex shape with a maximum height Ry of at least 50 µm and an average roughness Rz of at least 30 µm.