Folded Core Compression Modulus via Resin Optimization
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Solution Overview
Problem
Existing folded core structures in sandwich panels lack sufficient compression modulus, which is crucial for applications like aircraft and train flooring where weight and cost savings are essential, and traditional honeycomb structures are less economical.
Innovation Solution
A folded core structure with a nonwoven sheet impregnated with a thermoset resin, where the resin content is at least 50% of the total weight, and the nonwoven sheet has high modulus fibers and a specific apparent density, optimized for improved compression modulus and shear strength.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If traditional honeycomb structures are used, then compression modulus is insufficient, but weight and cost savings are reduced
Solution Approach 1:
The patent applies parameter changes by optimizing the resin content to at least 50 wt% and controlling the nonwoven sheet apparent density within a specific range (0.3-0.7 g/cm³). This resolves the contradiction by achieving high compression modulus through precise parameter control rather than increasing overall structure weight
Solution Approach 2:
The patent uses composite materials by combining high modulus fibers (modulus ≥ 200 g/denier) with thermoset resin in a nonwoven sheet structure. This composite approach achieves superior compression modulus compared to traditional honeycomb structures while maintaining weight efficiency
2Strength
If resin content is increased to improve compression modulus, then material cost increases, but structural integrity is improved
Solution Approach 1:
The patent optimizes resin content to a minimum of 50 wt% of combined weight, balancing compression modulus improvement with material usage. This parameter optimization resolves the contradiction by achieving high performance without excessive material consumption
Solution Approach 2:
The patent applies local quality by concentrating resin in specific regions where it provides maximum structural benefit for compression resistance. The resin is strategically distributed within the folded core structure to enhance stiffness where most needed
3Strength
If nonwoven sheet density is increased to improve compression properties, then manufacturing complexity increases, but compression modulus is enhanced
Solution Approach 1:
The patent controls nonwoven sheet apparent density within an optimized range (0.3-0.7 g/cm³) to achieve high compression modulus without excessive manufacturing complexity. This parameter control resolves the contradiction by finding the optimal density window that balances performance and manufacturability
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 optimized folded core structure achieves double the compression modulus compared to traditional methods while maintaining similar compression strength, providing enhanced stiffness and potential weight and cost savings.
Implementation Method 1
a nonwoven sheet and a cured resin in an amount such that the weight of cured resin as a percentage of combined weight of cured resin and nonwoven sheet is at least 50 percent
Implementation Method 2
fibers having a modulus of at least 200 grams per denier (180 grams per dtex) and a tenacity of at least 10 grams per denier (9 grams per dtex) wherein the optimized folded core structure achieves double the compression modulus
Data Source
Figure 1
AI summary
This invention is directed to a folded tessellated core structure having a high compression modulus. The core structure comprises a nonwoven sheet and a cured resin in an amount such that the weight of cured resin as a percentage of combined weight of cured resin and nonwoven sheet is at least 50 percent, The nonwoven sheet further comprises fibers having a modulus of at least 200 grams per denier (180 grams per dtex) and a tenacity of at least 10 grams per denier (9 grams per dtex) wherein, prior to impregnating with the resin, the nonwoven sheet has an apparent density calculated from the equation Dp = K x ((dr x (100 - %r)/%r)/(1 + dr/ds x (100 - %r)/%r), where Dp is the apparent density of the sheet before impregnation, dr is the density of cured resin, ds is the density of solid material in the sheet before impregnation, %r is the cured resin content in the final core structure in weight %, K is a number with a value from 1.0 to 1.5, Further, the Gurley porosity of the nonwoven sheet before impregnation with the resin is no greater than 30 seconds per 100 milliliters. The invention is also directed to composite structures incorporating such folded core.