FRP Reinforcing Member for Crack-Resistant Bolt Hole Joints
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Solution Overview
Problem
There is a need to suppress the generation and progression of cracks in bolted portions, rivet joints, and bent portions of fiber-reinforced plastic (FRP) molded bodies, which are prone to high-stress loads and low strength, especially around bolt holes and areas with small bending radii.
Innovation Solution
An FRP reinforcing member is created by integrating multiple laminated fiber layers with a resin, including spiral and lattice-patterned fiber layers, which are attached to the FRP molded body to cover bolt or rivet holes, using materials like glass, carbon, or aramid fibers, and connected using bolts or rivets with metal materials like iron-based or aluminum alloys.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Weight of moving object
If FRP molded bodies are made thinner and lighter to improve fuel efficiency, then weight is reduced, but strength and crack resistance in bolted portions deteriorate
Solution Approach 1:
The invention applies a reinforcing member with a thickness greater than the base FRP molded body specifically at the bolted portion, creating local reinforcement without increasing the overall thickness of the entire molded body. This allows the bulk of the structure to remain thin and lightweight while the critical connection areas gain enhanced strength and crack resistance.
Solution Approach 2:
The reinforcing member is constructed as a composite structure with a resin layer and a fiber layer, where the fiber layer contains fibers extending in multiple directions (radially and circumferentially) to provide multi-axis reinforcement. This composite approach optimizes strength-to-weight ratio by strategically placing high-strength fibers only where needed for crack resistance.
2Strength
If fiber layers are added to reinforce bolt holes, then strength around bolt holes is improved, but device complexity increases
Solution Approach 1:
The reinforcing member is designed as a separate, pre-fabricated component that can be independently manufactured and then attached to the FRP molded body. This segmentation allows the complex multi-directional fiber structure to be created once during reinforcing member production, rather than requiring complex layering operations during the main molded body manufacturing process.
Solution Approach 2:
The reinforcing member is prepared in advance with the appropriate fiber orientation and resin saturation before being attached to the FRP molded body. This preliminary preparation includes forming the fiber layers in the correct configuration (with radially and circumferentially extending fibers) and saturating them with resin prior to attachment, simplifying the overall manufacturing process.
3Reliability
If multiple fiber layers are laminated to suppress crack progression, then crack resistance is improved, but manufacturing complexity increases
Solution Approach 1:
The reinforcing member structure nests multiple fiber layers within a resin matrix, where the fiber layer is embedded within the resin layer. This nested configuration allows multiple layers to be integrated into a single unified component that can be manufactured as one piece through molding processes, rather than requiring separate attachment of multiple independent layers.
Solution Approach 2:
The invention specifies that the fiber layer should have fibers extending in multiple directions (radially and circumferentially) rather than a single direction, and that the thickness of the reinforcing member should be greater than the base FRP molded body. These parameter changes optimize crack resistance by distributing stresses in multiple directions and providing sufficient material depth to arrest crack propagation.
Data Source
AI summary
An FRP reinforcing member configured to be used by being attached to an FRP molded body is provided with a plurality of laminated fiber layers being integrated with a resin. An FRP connecting structure includes FRP molded bodies being connected to each other or an FRP molded body and a member made of a material different from the FRP being connected to each other, by a bolt or a rivet. The FRP reinforcing member is attached to the FRP molded body so as to cover a periphery of a bolt hole or a rivet hole of the FRP molded body. An FRP molded body includes a recess or a hole formed on a surface. The FRP reinforcing member is mounted to the FRP molded body so as to cover an opening of the recess or the hole. An FRP reinforcing member producing method includes charging a plurality of fiber layers composed of glass fibers, carbon fibers, or aramid fibers and a resin into a mold, pressing the plurality of fiber layers and the resin at 300° C. or less for 60 minutes or less, and removing a load pressure, cooling, and then demolding after the pressing.