Stamp-Formed Thermoplastic Composite Assembly With Integrated Spar Bonding
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Solution Overview
Problem
Conventional methods for forming thermoplastic composite closed-contoured structures, such as wing boxes, involve separate formation of skins and spars, leading to multiple steps and tolerance issues during assembly.
Innovation Solution
A method of co-consolidating a fiber-reinforced thermoplastic composite assembly by applying low-melt films on spar interfaces and skins, using tooling segments to position spars, heating to specific temperatures, and stamp-forming the assembly in a single step to integrate spars and skins.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If skins and spars are formed separately and then assembled, then manufacturing flexibility is maintained, but the number of process steps increases and tolerance issues arise
Solution Approach 1:
The patent merges the formation of skins and spars into a single stamp-forming process. Pre-formed spars with low-melt film are positioned on tooling segments, and skin blanks are draped over them. When heated and pressed, the low-melt film melts and bonds the skin to the spar interfaces, creating an integrated assembly in one operation rather than separate formation and assembly steps.
Solution Approach 2:
The spars are pre-formed before the main stamp-forming operation. This preliminary action allows the spars to be prepared with precise dimensions and low-melt film coating in advance, so they can be quickly positioned and integrated with the skin during the single stamp-forming step, reducing overall process complexity.
2Ease of manufacture
If skins and spars are formed separately and then assembled, then manufacturing flexibility is maintained, but tolerance issues occur in closed-contoured assemblies
Solution Approach 1:
By combining skin and spar formation into a single stamp-forming operation, the patent eliminates the separate assembly step that causes tolerance accumulation. The low-melt film bonding occurs in-situ during stamp-forming, ensuring precise alignment and integration of spars with the skin in closed-contoured assemblies like wing boxes.
3Strength
If multiple fastening or welding steps are used to secure spars to skin, then structural strength is ensured, but process time and complexity increase
Solution Approach 1:
The patent utilizes the phase transition of the low-melt film from solid to liquid state during heating. The film melts at a temperature below the spar resin melt temperature, creating a liquid bonding phase that flows and adheres the skin to the spar interfaces. Upon cooling, it solidifies to form a strong bond, replacing multiple fastening or welding operations with a single thermal bonding process.
4Productivity
If a single stamp-forming action is used to co-consolidate skin and spars, then process steps are reduced, but precise temperature control is required
Solution Approach 1:
The low-melt film has a melting temperature specifically designed to be below the spar resin melt temperature. This local property difference allows selective melting of the bonding film at the skin-spar interfaces while keeping the structural spar resin intact. The temperature control requirement is localized to the bonding film rather than the entire assembly, simplifying the thermal process.
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
Reduces the number of process steps and minimizes tolerance issues by integrating spars and skins in a single stamp-forming process, resulting in precise, closed-contoured structures like wing tips and rotor blades.
Implementation Method 1
heating the at least one tooling segment to cause the first low-melt film to reach a first temperature, wherein the first temperature is above a crystallization temperature of the first low-melt film
Implementation Method 2
the first temperature is above a crystallization temperature of the first low-melt film and below a melt temperature of a thermoplastic spar resin
Implementation Method 3
heating a skin blank to a second temperature above a melt temperature of a thermoplastic skin resin of the skin blank
Implementation Method 4
the skin blank and any second low-melt film on it may be heated to the point that the skin blank may draped or placed around the at least one tooling segment
Implementation Method 5
closing a stamp press around the skin blank and the at least one tooling segment, thereby pressing the skin blank into the at least one tooling segment and pressing the skin blank against the first low-melt film
Implementation Method 6
pressing the skin blank against the first low-melt film on the at least one interface surface of the spar(s)... co-consolidating the skin blank and the at least one spar within the stamp press
Data Source
AI summary
Stamp-forming a composite assembly includes applying a low-melt film on an interface surface of at least one spar, loading the spar onto at least one tooling segment such that the interface surface is exposed, and heating the tooling segment to a first temperature that is above a crystallization temperature of the low-melt film and below a melt temperature of a resin of the spar. A second low-melt film may be applied on a fiber-reinforced thermoplastic skin blank, and the skin blank is heated to a second temperature above a melt temperature of a resin of the skin blank. The skin blank is then draped around the tooling segment such that at least some of any second low-melt film contacts the low-melt film on the interface surface of the spar. The stamp press is then closed to co-consolidate the skin blank and the spar, thereby stamp-forming the composite assembly.