Fiber-Reinforced Plastic Joining via Thermoplastic Surface Layer
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Solution Overview
Problem
Existing fiber-reinforced plastics face challenges in achieving high joining strength and reliability of the joining structure, particularly due to stress concentration and peeling issues at the interface between different resin layers.
Innovation Solution
A fiber-reinforced plastic composite structure is developed, featuring a thermosetting resin layer with a sea-island structure and a thermoplastic resin layer as the surface layer, where the interface between the two resin layers is positioned inside the reinforcing fiber group, enhancing mechanical bonding and toughness.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If a thermoplastic resin layer is disposed on the surface of fiber-reinforced plastic to enable joining without drilling or adhesives, then joining strength is improved, but stress concentration occurs at the interface between thermoplastic resin layer and thermosetting resin layer due to poor toughness of thermosetting resin
Solution Approach 1:
The patent applies local quality by creating a sea-island structure where thermoplastic resin islands are dispersed within the thermosetting resin matrix. This allows different regions to have different properties: the thermoplastic resin islands provide toughness and stress distribution, while the thermosetting resin provides structural integrity. The interface between resin layers is positioned inside the reinforcing fiber group, creating localized zones of enhanced bonding and stress distribution throughout the composite structure.
Solution Approach 2:
The patent uses composite materials by combining thermoplastic resin and thermosetting resin in a sea-island structure. This composite approach allows the material to exhibit both the toughness and stress-distribution capabilities of thermoplastic resin and the structural strength and rigidity of thermosetting resin, resolving the contradiction between joining strength and reliability.
2Strength
If mechanical joining methods by bolts, rivets, or screws are used to integrate fiber-reinforced plastics with other members, then joining is achieved, but strength of the hole is reduced and processability deteriorates due to pre-processing steps
Solution Approach 1:
The patent replaces mechanical joining methods (bolts, rivets, screws) with a thermal-mechanical bonding system. The thermoplastic resin layer is heated to melt and bond directly to the thermosetting resin layer, eliminating the need for mechanical fasteners and associated pre-processing steps like hole drilling. This substitution maintains joining strength while significantly improving ease of manufacture.
3Strength
If adhesives are used to join fiber-reinforced plastics to other members, then joining is achieved, but joining and adhesion failure occurs due to peeling at the interface
Solution Approach 1:
The patent changes the physical state parameter of the thermoplastic resin from solid to molten and back to solid through controlled heating and cooling. This phase transition enables the resin to flow and penetrate the interface region, creating a metallurgical-like bond between layers that is far more reliable than adhesive bonding. The resulting joint has superior adhesion reliability and resistance to peeling forces.
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 proposed solution achieves excellent joining strength and reliability by distributing stress evenly and preventing crack propagation, while also simplifying the joining process by eliminating the need for drilling or adhesives.
Implementation Method 1
it is possible to melt the thermoplastic resin layer to join another adherend to the fiber-reinforced plastic
Implementation Method 2
The thermoplastic resin present as a continuous phase in the adhesive resin layer acts as an anchor to firmly join the thermoplastic resin in the adhesive resin layer to the thermosetting resin
Data Source
AI summary
The present invention relates to a fiber-reinforced plastic that includes a reinforcing fiber group, a thermosetting resin layer, and a thermoplastic resin containing a first thermoplastic resin, wherein the fiber-reinforced plastic has the thermoplastic resin layer as the surface layer of the fiber-reinforced plastic, the interface between the thermoplastic resin layer and the thermosetting resin layer is located inside the reinforcing fiber group, and the thermosetting resin layer has a sea-island structure in which an island phase having a second thermoplastic resin or a rubbery polymer as the main component is dispersed in a sea phase having a thermosetting resin as the main component.