Conical Load Spreader for Composite Fan Platform
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Current mechanical attachment methods for securing composite fan platforms to metal disks in low radius hub designs limit the reduction of fan hub radius, restricting airflow and overall engine performance.
Innovation Solution
A bolted joint using a conical metal load spreader and filler ring to secure a composite fan platform to a metal disk, with a mounting feature featuring increased section thickness, conical countersinks, and dual platform mounting holes, allowing for a low radius hub design while enhancing strength and fatigue life.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Length of moving object
If traditional mechanical attachment methods are used to secure composite fan platforms to metal disks, then the joint strength is sufficient for basic operation, but the fan hub radius cannot be reduced further, limiting airflow and engine performance
Solution Approach 1:
The conical load spreader concentrates the bolt load into a localized conical area on the composite platform, distributing stress locally rather than across the entire joint interface. This localized stress distribution allows the joint to maintain sufficient strength while enabling the overall hub radius to be reduced, as the critical stress concentration points are controlled and managed through the conical geometry.
Solution Approach 2:
The solution utilizes a composite fan platform made of carbon fiber reinforced polymer (CFRP) materials that can be molded with integrated conical countersinks and mounting features. The composite material provides high strength-to-weight ratio and allows complex geometries to be formed in a single manufacturing process, enabling the reduced hub radius design while maintaining joint strength through material properties rather than increased joint size.
2Productivity
If the fan hub radius is reduced to improve airflow and engine performance, then airflow area increases and performance improves, but the space for platform interface and mounting features is limited
Solution Approach 1:
The conical load spreader introduces a third dimension (conical depth) to the mounting interface, allowing the joint to develop strength through axial compression and radial distribution rather than relying solely on the limited radial interface area. This dimensional transformation enables sufficient joint strength with minimal radial space, facilitating the reduced hub radius design.
Solution Approach 2:
The mounting feature is segmented into distinct functional zones: the conical countersink for load distribution, the through-hole for bolt insertion, and the reinforced transition portion for structural integrity. This segmentation allows each zone to be optimized independently, maximizing the utility of the limited interface area while maintaining overall joint strength.
3Ease of manufacture
If conventional joint designs are used, then the assembly is simple to manufacture, but performance penalties occur due to joint interference in the airflow path
Solution Approach 1:
The conical load spreader, mounting hole, and reinforcement features are merged into a single integrated composite platform component manufactured in one molding operation. This eliminates the need for separate metal reinforcement plates, multiple assembly steps, and complex fastening procedures, maintaining ease of manufacture while creating a smooth aerodynamic surface that eliminates airflow interference.
4Strength
If the transition portion thickness is increased to provide sufficient material for mounting holes and countersinks, then joint strength improves, but the overall platform mass increases
Solution Approach 1:
The use of carbon fiber reinforced polymer composite materials provides exceptional strength-to-weight ratio, allowing the transition portion to be sufficiently thick for mounting features while keeping the overall mass low. The composite material's anisotropic properties can be optimized during molding to provide enhanced strength precisely where needed for the mounting holes and countersinks, rather than uniformly increasing thickness throughout the platform.
Data Source
AI summary
Composite fan blade platform includes forward and aft portions and transition portion therebetween. Platform mounting holes extend through increased section thickness in transition portion and conical countersinks centered about centerlines of mounting holes extend into transition portion. Bolts include bolt shanks extending away from boltheads through center bolt holes in conical load spreaders in conical countersink. Boltheads engage conical load spreader. Bolthead is disposed entirely within cylindrical counterbore into top of load spreader and engages shoulder at bottom of cylindrical counterbore. Radial gap between bolthead and cylindrical counterbore surface of cylindrical counterbore may be filled by filler or filler ring. Bolts may join platform supports to disk hooks attached, fixed or joined to, or integral with disk posts of disk. Nuts threaded on threaded inner end of bolt shank may secure bases attached to platform supports to fan blade platform.