Composite Prepreg With Segmented Resin Regions For Joining
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Solution Overview
Problem
Current joining techniques for thermosetting fiber-reinforced composite materials face challenges in achieving strong and reliable bonds, particularly when using thermosetting resins, as they tend to have insufficient joining strength due to curing reactions that prevent remelting and bonding with other members.
Innovation Solution
A composite prepreg is developed with distinct regions of thermosetting resins having different gel times and heat generation starting temperatures, allowing for controlled curing and improved bonding strength by maintaining the thermosetting resin (b) in an uncured state while thermosetting resin (a) is cured, ensuring excellent joining strength and heat resistance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If thermosetting resin is sufficiently heated and cured to achieve heat resistance, then heat resistance is improved, but joining strength deteriorates because the cured resin does not remelt and bond with other members
Solution Approach 1:
The prepreg is divided into two distinct regions: a first region containing thermosetting resin (a) that cures at lower temperature, and a second region containing thermosetting resin (b) that remains uncured during the same heating process. This segmentation allows different parts of the same material to have different curing states, enabling heat resistance in the first region while maintaining joinability in the second region.
Solution Approach 2:
Different regions of the prepreg are given different local properties through the use of different thermosetting resins with different gel times. The first region has fast-gelling resin for heat resistance, while the second region has slow-gelling resin for joining. This local differentiation resolves the contradiction by allowing each region to optimize for its specific function.
2Temperature
If thermosetting resin is used to maintain heat resistance, then heat resistance is improved, but ease of manufacture deteriorates because joining to multiple members becomes difficult when curing has sufficiently proceeded
Solution Approach 1:
The prepreg is segmented into first and second regions with different curing characteristics. The second region with slow-gelling resin remains workable and can be joined to multiple members even after the first region has cured. This segmentation enables multi-member joining operations to proceed without being constrained by the curing of the heat-resistant region.
Solution Approach 2:
The first region cures in advance during the initial heating stage, establishing heat resistance before the second region is needed for joining operations. This preliminary curing action allows subsequent joining steps to be performed on the uncured second region without compromising the already-cured first region.
3Ease of manufacture
If adhesive joining method is used to join fiber-reinforced composite materials, then ease of manufacture is improved, but reliability deteriorates due to joining failure from peeling at the boundary surface
Solution Approach 1:
The invention changes the fundamental parameter of the joining interface from adhesive-bonded to thermally-bonded through remelting. By using thermoplastic resin at the joining surface, the material transitions from a chemical bond (adhesive) to a physical bond (thermal fusion), eliminating peeling failures and improving reliability while maintaining ease of manufacture.
Solution Approach 2:
The prepreg combines thermosetting resin (for heat resistance and structural integrity) with thermoplastic resin (for reliable joining). This composite material structure allows the thermosetting resin to provide heat resistance while the thermoplastic resin provides reliable, peel-resistant joining through thermal fusion.
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 composite prepreg enables easy and strong joining of thermosetting fiber-reinforced composite materials to other members, enhancing the degree of freedom in design and productivity while maintaining excellent heat resistance and joining strength.
Implementation Method 1
a first region (6) containing a thermosetting resin (a) and a reinforcing fiber (3), and a second region (7) containing a thermosetting resin (b) and a reinforcing fiber (5)
Implementation Method 2
a joint surface is remelted and peeled off at a high temperature
Data Source
AI summary
Provided is a composite prepreg including a region (A) containing a thermosetting resin (a) and a reinforcing fiber and a region (B) containing a thermosetting resin (b) and a reinforcing fiber, the composite prepreg satisfying conditions (i) and (ii) or satisfying conditions (ii) and (iii):(i) The thermosetting resin (b) is a resin having a gel time Tb longer than a gel time Ta of the thermosetting resin (a), and in at least a part of a temperature range of 40° C. or more and 180° C. or less, satisfy Ta/Tb≤0.8;(ii) A ratio of the region (A) on a surface of the composite prepreg is 20 to 80%; and(iii) The thermosetting resin (b) is a resin having a higher heat generation starting temperature Eb than a heat generation starting temperature Ea of the thermosetting resin (a), and in a differential scanning calorimetry chart obtained by measuring at 5° C./min with 40° C. as a starting temperature, satisfy Eb−Ea≥30.