Fan Blade Adhesive Bond Segmentation for Impact and Durability
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Solution Overview
Problem
Existing adhesives for bonding aluminum fan blades in geared turbofan engines either lack flexibility for impact resistance or durability at elevated temperatures, making it difficult to achieve high bond strength, environmental durability, and resistance to bond-line damage growth simultaneously.
Innovation Solution
A dual-adhesive system is employed, where a first adhesive region near the blade tip provides flexibility and impact resistance using a polyurethane elastomer, and a second adhesive region near the blade root offers enhanced environmental durability with a polyepoxide adhesive, with the second adhesive being less susceptible to moisture.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If an elastomer-based adhesive is used to bond the aluminum cover to the aluminum blade body, then flexibility and impact resistance are improved, but bond strength at elevated temperatures and environmental durability deteriorate
Solution Approach 1:
The adhesive bond is segmented into two distinct adhesive regions: a first adhesive region containing an elastomer-based adhesive for impact resistance, and a second adhesive region containing an epoxy-based adhesive for environmental durability. This segmentation allows each adhesive type to be applied where its specific properties are most beneficial, resolving the contradiction between flexibility and durability.
Solution Approach 2:
Different adhesive compositions are applied to different locations on the blade cover bond. The elastomer-based adhesive is applied in the first adhesive region where impact resistance is prioritized, while the epoxy-based adhesive is applied in the second adhesive region where environmental durability is prioritized. This local differentiation of material properties resolves the contradiction by optimizing each region for its specific functional requirements.
2Reliability
If an epoxy-based adhesive is used to bond the aluminum cover to the aluminum blade body, then bond strength at elevated temperatures and environmental durability are improved, but flexibility and impact resistance deteriorate
Solution Approach 1:
The adhesive bond is divided into two adhesive regions with different epoxy-based adhesive compositions. The first adhesive region uses an elastomer-based adhesive for impact resistance, while the second adhesive region uses an epoxy-based adhesive for environmental durability. This segmentation allows the epoxy-based adhesive to provide its superior durability where needed without requiring it to provide impact resistance everywhere.
Solution Approach 2:
The epoxy-based adhesive is applied locally in the second adhesive region where environmental durability is the primary concern, rather than uniformly across the entire bond area. This local application allows the epoxy to excel at providing temperature and moisture resistance without the penalty of reduced flexibility affecting the entire blade assembly.
3Device complexity
If a single adhesive type is used for the entire blade cover bond, then device complexity is reduced, but the ability to achieve high bond strength, environmental durability, and impact resistance simultaneously deteriorates
Solution Approach 1:
Rather than using a single adhesive type uniformly, the bond is segmented into two adhesive regions with different adhesive compositions. This segmentation increases performance reliability by matching adhesive properties to functional requirements in different locations, accepting the moderate increase in application complexity as necessary for achieving the required overall bond performance.
Solution Approach 2:
The adhesive system uses a composite approach by combining two different adhesive compositions (elastomer-based and epoxy-based) in a single bond joint. This composite adhesive system leverages the complementary strengths of each adhesive type to achieve overall bond performance that neither adhesive could provide alone, resolving the contradiction between simplicity and performance.
Data Source
AI summary
Disclosed herein is a blade for a turbine comprising a blade cover; a blade body; and a layer of adhesive disposed between the blade cover and the blade body; where the layer of adhesive comprises a first adhesive region and a second adhesive region; where the first adhesive region comprises an adhesive that is chemically different from an adhesive used in the second adhesive region.