Laminated Metal Fastening Inclusion for Hole-Free Composite Joints
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Solution Overview
Problem
Current methods for joining fiber reinforced polymers to other structures, such as adhesive bonding and mechanical fastening, face limitations including weak adhesive joints and damage to the composite from hole creation for fasteners, leading to increased material usage and manufacturing complexity, especially in integrating composites into vehicles.
Innovation Solution
Integrating a laminated metal fastening inclusion with a coalesced hard point and flanges into the fiber reinforced polymer structure before curing, using Ultrasonic Additive Manufacturing, to create a strong mechanical joint that engages the entire thickness of the composite and allows for precise fastener placement without damaging the fibers.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If mechanical fasteners are used to join fiber reinforced polymers, then strong mechanical interlocking is achieved, but the composite is weakened due to hole creation and fiber damage
Solution Approach 1:
The patent applies preliminary action by embedding the fastener within the composite structure during the manufacturing process before the composite is cured. The fastener is placed in a recess formed in the composite, and the composite is then cured around the fastener. This preliminary placement allows the fastener to be integrated into the composite structure without requiring post-curing hole creation, thereby avoiding fiber damage and maintaining composite integrity while still achieving strong mechanical interlocking.
2Strength
If adhesive bonding is used to join fiber reinforced polymers, then clean surfaces and precise alignment are required, but the joint strength is limited by the matrix material strength
Solution Approach 1:
The patent merges adhesive bonding with mechanical fastening by combining an adhesive layer with a mechanically embedded fastener. The adhesive is applied to the fastener and/or composite surfaces, and the fastener is then embedded into the composite during curing. This combination provides both the chemical bonding of adhesive and the mechanical interlocking of the fastener, achieving superior joint strength that overcomes the limitation of adhesive-only joints being restricted by matrix material strength.
3Reliability
If co-molded fasteners are used in the composite, then fiber damage is avoided, but the fastener location is fixed and dimensional tolerance is very small
Solution Approach 1:
The patent applies dynamics by making the fastener location adjustable after the composite is cured. Instead of fixing the fastener position during molding, the method allows the fastener to be repositioned within the recess in the cured composite. This dynamic adjustment capability provides dimensional tolerance compensation, allowing the fastener to be located precisely during assembly even if the composite manufacturing has variations, thereby overcoming the rigid fixed-position limitation of co-molded fasteners.
4Strength
If through-holes are created for mechanical fasteners, then load transfer through mechanical interlocking is achieved, but material usage increases due to knock-down factor
Solution Approach 1:
The patent applies preliminary action by forming a recess in the composite and embedding the fastener within this recess during the curing process, rather than creating through-holes after curing. This preliminary embedding allows the fastener to be surrounded by composite material, distributing stresses more effectively and eliminating the need for additional material thickness (knock-down factor) that would otherwise be required to compensate for the weakening effect of through-holes. The result is reduced material usage while maintaining load transfer capability.
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
This method provides a strong, durable joint that reduces the need for additional fasteners and manufacturing precision, minimizing material usage and weight while maintaining structural integrity, and allows for wider dimensional tolerances in assembly.
Implementation Method 1
Integrating a laminated metal fastening inclusion with a coalesced hard point and flanges into the fiber reinforced polymer structure before curing, using Ultrasonic Additive Manufacturing
Implementation Method 2
curing the fiber reinforced resin plies to bind the layers to the flanges
Data Source
AI summary
A fastening inclusion is provided and includes a hard point made of coalesced metal sheets, metal or fiber flanges extending from edges of the hard point, and a fastener arranged on the hard point. The fastening inclusion can be incorporated into a fiber reinforced polymer structure by interleaving the flanges with fiber reinforced resin plies, and then curing the fiber reinforced plies to form a composite structure. The fastener on the hard point may be used for mechanically connecting the composite structure to a separate component, such as a metal component on a vehicle.