Interlocking Tooth Bond for Composite Laminate Assembly
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Solution Overview
Problem
Fiber composite laminates have low damage tolerance and are challenging to join efficiently, leading to bulk, weight, and cost issues due to their susceptibility to interlaminar failures and delamination, especially in bonded and bolted joints.
Innovation Solution
A method of joining fiber composite laminates through a low-profile adhesive bond using interlocking or non-interlocking teeth that eliminates peel and reduces interlaminar stresses, allowing for end-to-end joining without additional laminate build-up, with optional cover plies for added strength and damage indication, and providing energy absorption and failsafe capabilities.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If bonded joints are used to join fiber composite laminates, then the joint can be formed with adhesive bonding, but the joint loads the laminates across weak interlaminar interfaces causing delamination and interlaminar failures
Solution Approach 1:
The end of the laminate is segmented into multiple teeth (e.g., 3-6 teeth per end) that interlock with corresponding teeth on the adjacent laminate. This segmentation creates multiple discrete bonding points distributed along the joint length, eliminating the continuous weak interlaminar interface that causes delamination in conventional bonded joints. Each tooth creates a localized bond that is stronger than the surrounding laminate, preventing crack propagation through the joint.
Solution Approach 2:
The joint configuration transitions from a conventional planar bonded interface to a three-dimensional interlocking tooth structure. The teeth extend through the thickness of the laminate, creating bonds in the longitudinal dimension while distributing loads across multiple discrete points. This dimensional change transforms the failure mode from interlaminar delamination to tooth root failure, which is more reliable.
2Device complexity
If single lap joints are used to join fiber composite laminates, then the joint structure is simple, but tension loads cause the laminates to peel away resulting in interlaminate delamination
Solution Approach 1:
The simple lap joint configuration is enhanced by segmenting the bonding interface into discrete interlocking teeth. This segmentation prevents the continuous peel propagation that occurs in conventional single lap joints by creating multiple discrete bond points that must fail sequentially under tension loads, thereby maintaining laminate integrity.
Solution Approach 2:
The joint combines adhesive bonding materials with a mechanical interlocking tooth structure. This composite approach merges the simplicity of adhesive bonding with the peel resistance of mechanical interlocking, creating a joint that is both structurally simple and highly resistant to tension-induced delamination.
3Strength
If double lap joints with cover plies are used to join fiber composite laminates, then the joint can carry tension loads, but the outermost layers bear most of the load resulting in adhesive failure or interlaminar shear failure at the ends of cover plies
Solution Approach 1:
The load-bearing structure is segmented into multiple discrete teeth distributed along the joint length, eliminating the concentration of load at the ends of cover plies. Each tooth independently carries a portion of the tension load, distributing stresses uniformly across the joint and preventing the adhesive failure or interlaminar shear failure that occurs in conventional double lap joints.
Solution Approach 2:
The tooth structure creates localized reinforcement at specific bonding points rather than uniformly distributing cover plies throughout the entire joint. This local quality enhancement concentrates the strength where needed (at the tooth roots) while maintaining the simplicity of the overall joint configuration.
4Area of stationary object
If scarf joints are used to join fiber composite laminates, then the surface area for bond interface is increased, but the scarf angle must be very low making the joint difficult and expensive to fabricate
Solution Approach 1:
Instead of creating a long continuous scarf interface requiring very low angles, the bonding area is segmented into discrete tooth structures. Each tooth provides a localized bonding zone with optimal geometry, eliminating the need for extensive scarfing operations while maintaining sufficient bond interface area for strong adhesive bonding.
Solution Approach 2:
The conventional mechanical scarfing process (which requires precise low-angle cutting) is replaced by a tooth-based bonding system that can be fabricated using standard laminate layup and curing processes. This substitution eliminates the complex fabrication requirements of scarf joints while providing adequate bond surface area through the tooth structures.
5Reliability
If bolted joints are used to join fiber composite laminates, then damage tolerance is improved, but precise hole alignment and precise diameter drilling are required which is difficult and expensive
Solution Approach 1:
The bolted joint system is replaced with a segmented tooth-based adhesive bond that does not require precise hole alignment or diameter control. The teeth are formed as integral parts of the laminate structure during manufacturing, eliminating the need for post-manufacturing precision drilling and alignment operations while maintaining high damage tolerance through the distributed tooth root anchorages.
Solution Approach 2:
The mechanical bolted joining system (requiring precise threaded holes and alignment) is replaced with a tooth-based adhesive bonding system. This substitution eliminates the precision drilling and alignment requirements of bolted joints while providing comparable or superior damage tolerance through the distributed tooth structures that resist crack propagation.
6Ease of manufacture
If overlapping ends of laminates are used in bonded or bolted joints, then the joint can be formed, but additional bulk and weight are added to the structure
Solution Approach 1:
The joint configuration transitions from a conventional overlapping lap joint to an end-to-end tooth interlocking configuration. The teeth extend through the laminate thickness, creating bonds in the longitudinal dimension without requiring the laminates to overlap in the transverse direction. This dimensional change eliminates the additional bulk and weight associated with conventional overlapping joints while maintaining strong bonding.
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 significantly reduces interlaminar failures, increases damage tolerance, and achieves higher specific strengths and energy absorption, while being weight-efficient and aerodynamically smooth, with predictable performance even after damage, and the ability to modify tooth profiles for different performance characteristics.
Implementation Method 1
a low-profile adhesive bond for structurally splicing two fiber composite panels together
Data Source
AI summary
An improved method of joining fiber composite laminates is disclosed. Two fiber composite laminates may be joined together end-to-end. The bonding is done through the thickness of the fiber composite laminates. There are two ways to form the bond: (1) non-interlocking; and (2) interlocking.