Composite Filler With Non-Bondable Core
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Solution Overview
Problem
Composite fillers in aircraft structures are prone to cracking due to tensile forces caused by differential thermal expansion, which reduces the structural performance and increases the cost of rework or replacement.
Innovation Solution
A composite filler is designed with a non-bondable core and spirally wrapped composite layers to reduce stress concentrations and absorb thermal and chemical shrinkage strains, preventing cracking, and the core is removable to reduce weight after curing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of moving object
If the cross-section of the filler is increased to fill larger gaps, then the gap-filling capability is improved, but the propensity to crack increases due to higher tensile forces from differential thermal expansion
Solution Approach 1:
The filler is segmented into multiple layers with different material properties. The inner layer uses a material with thermal expansion properties matching the substrate, while outer layers use composite materials. This segmentation allows each layer to handle different stress conditions, preventing crack propagation through the entire filler structure.
Solution Approach 2:
Different regions of the filler have different material compositions tailored to local requirements. The inner layer near the substrate uses materials optimized for thermal matching, while outer layers use composite materials optimized for structural strength and gap-filling. This local quality optimization allows the filler to simultaneously handle thermal stresses and provide structural support without cracking.
2Ease of manufacture
If composite material layers are applied directly to each other to form the filler, then manufacturing simplicity is improved, but manufacturing precision deteriorates due to difficulty in achieving consistent layer bonding and uniform thickness
Solution Approach 1:
An intermediate layer or interface treatment is introduced between composite material layers to improve bonding consistency. This intermediary layer ensures uniform adhesion between layers, preventing delamination and ensuring consistent mechanical properties throughout the filler structure, thereby improving manufacturing precision without complicating the application process.
Solution Approach 2:
The manufacturing process controls parameters such as layer thickness, curing temperature, and pressure to ensure consistent bonding between layers. By precisely controlling these parameters, the process achieves uniform layer integration and consistent filler properties, resolving the contradiction between ease of manufacture and manufacturing precision.
3Strength
If the filler is made from solid composite material to ensure structural strength, then strength is improved, but weight increases which contradicts the lightweight design goals of composite aircraft structures
Solution Approach 1:
The filler uses composite materials consisting of reinforcing fibers embedded in a polymer resin matrix. This composite structure provides high structural strength-to-weight ratio, maintaining the lightweight advantage of composite aircraft structures while ensuring the filler has sufficient strength to withstand thermal and mechanical loads without cracking or failing.
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 solution effectively reduces the likelihood of cracking in composite fillers, enhancing structural performance and reducing costs associated with rework or replacement, while also minimizing weight by removing the core post-curing.
Implementation Method 1
absorb thermal and chemical shrinkage strains
Implementation Method 2
absorb thermal and chemical shrinkage strains
Implementation Method 3
spirally wrapped around a core
Data Source
AI summary
A method and apparatus is presented. The composite filler comprises a number of layers of composite material and a core comprising a material which is non-bondable with the composite material.