Sandwich Panel Fastening Hole Reinforcement Against Resin Cracking
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Solution Overview
Problem
Existing panels with honeycomb or foam cores face issues with forming fastening holes due to core weakness under local loads, leading to resin cracking during heating and cooling processes, as the resin expands and contracts, compromising the reinforcement of the fastening hole periphery.
Innovation Solution
A method involving through-hole formation in the core, filling it with a resin containing reinforcing fibers, and bonding skins to both core surfaces, which includes steps like elastic body or adhesive agent use to manage resin expansion and contraction, ensuring the resin's toughness and suppressing cracking.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If the core is filled with resin to reinforce the fastening hole periphery, then the reinforcement strength is improved, but the resin cracks during heating and cooling processes
Solution Approach 1:
The patent uses a composite material consisting of resin and rubber particles dispersed within it. The rubber particles (1-50 μm diameter) are distributed in the resin matrix to form a composite structure that combines the adhesive properties of resin with the elasticity and crack-resistance of rubber, preventing resin cracking during thermal cycling while maintaining reinforcement strength
Solution Approach 2:
The patent modifies the physical and chemical parameters of the resin by incorporating rubber particles, which changes the resin's mechanical properties including its elasticity, tensile strength, and resistance to thermal stress. This parameter modification allows the resin to withstand expansion and contraction during heating and cooling without cracking
2Strength
If a through-hole is formed in the core for resin filling, then the fastening hole reinforcement is enabled, but the core structure is weakened
Solution Approach 1:
The patent applies local quality by forming through-holes only in specific regions where fastening holes will be located, rather than uniformly throughout the core. The resin-filled regions are localized to provide reinforcement exactly where needed (at fastening hole peripheries), while the rest of the core maintains its original structural integrity
Solution Approach 2:
The core is segmented into multiple regions: regions with through-holes filled with resin-composite for fastening reinforcement, and regions without through-holes that maintain the original core structure. This segmentation allows the core to provide reinforcement where needed while preserving overall structural strength
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 method enhances the resin's strength around fastening holes, preventing cracking and maintaining structural integrity by improving resin toughness and managing thermal stress through controlled expansion and contraction.
Implementation Method 1
when the panel filled with the resin is heated... as indicated by white arrows in the left diagram, a resin 220 is compressed on the lower skin 230 side, and the resin 220 expands on the upper skin 230 side. As illustrated in the left diagram, when the resin 220 expands, a through-hole 210a for resin filling formed in a core 210 is enlarged
Implementation Method 2
in the cooling process, although the resin 220 is contracted, after the heating process, the core 210 is bonded to the skins 230, and the shape of the through-hole 210a does not substantially change. As a result, as indicated by the white arrows in the right diagram, tensile stress is generated between the resin 220 and the core 210
Data Source
Figure 1~2
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AI summary
Provided is a panel in which it is possible to satisfactorily ensure the strength of a resin reinforcing the periphery of a fastening hole. This method for manufacturing a panel (100) in which outer plates (20) are fixed to both surfaces of a core (10) having a plurality of cavities comprises: a through-hole formation step for forming a through-hole (12) in the core (10) within a range including a formation position at which a fastening hole (30) is to be formed in the panel (100); a filling step for filling the through-hole (12) with a resin (13) containing a glass filler (14) as reinforcing fibers including at least short fibers; and a panel-formation step for positioning the outer plates (20) on both surfaces of the core (10), performing a heat treatment on the core (10) and the outer plates (20), and joining the core (10) and the outer plates (20) to form a panel.