Tailored Fiber Placement for Complex Preforms

The problem it set out to solve

The report's own framing is that TFP's biggest obstacle was never the machinery — it was evidence. Engineers were being asked to design primary, highly loaded structure around a process with very little commercial or non-proprietary structural performance data behind it, and without robust analytical tools to optimise fiber architecture and predict how a given preform would behave.

The programme was structured to close that gap: characterise the material properly, validate analytical tools against physical tests, and generate cost and performance data on components industry sponsors actually cared about.

What was tested

The work focused on high-strength carbon fiber — T700 among others — with aerospace epoxy resin systems, aimed at vehicle, aerospace and industrial applications. It followed a building-block approach, starting from standardised ASTM coupon testing and working up through progressively more representative sub-elements:

• Interlaminar tensile, Mode I and Mode II fracture toughness across a range of stitch densities
• Tensile modulus and strength at 0° and 90°
• Curved beam strength and beam shear performance
• Bearing performance of TFP inserts at varying tow sizes
• A large-scale TFP lug, including a metallic hard-point insert
• A fully TFP clip bracket designed against an existing metallic part

Computed tomography was used to characterise the fiber distortions introduced by the stitching itself, and those distortions were fed back into the models rather than idealised away.

What it found

The report lists four outcomes: novel analytical tools were developed and demonstrated for analysing TFP preforms; a building-block approach using coupons and sub-elements was shown to work for optimising a more complex component; optimised fiber orientation via TFP was shown to be able to exceed the performance of conventional textile composites, opening applications currently restricted to metallic parts; and both performance and cost benefits were demonstrated against metallic and conventional textile baselines.

On predictive accuracy, the authors report that the toolset showed excellent agreement with experimental failure loads and damage locations — which is the part that matters if you intend to design with the process rather than test your way to a part.

The cost model

The clip bracket was used as the cost case, because the aluminium baseline was well understood at $150 per part. The team built up a TFP figure from materials (roughly $2.10 per part), stitching labour (about $5 per preform, based on one technician running two eight-head machines), trimming (around $0.50), and an amortised work-cell overhead (about $2 per preform at roughly 100,000 preforms a year) — just under $10 to produce the preform. Adding moulding, estimated at $68 per unit, brought total manufacturing cost to about $78 per unit, close to half the cost of the aluminium part.

The authors are explicit that overhead, depreciation and maintenance were not well characterised and that scrap was assumed to offset low-volume material pricing, so the figure is a directional model rather than a quote.

What the authors recommend next

The report's open questions are as informative as its results. It recommends developing design allowables covering high temperature/moisture exposure and saturation under load — noting that moisture uptake in the backing cloths and reinforcing threads is hard to predict computationally. It recommends tracking how stitching needle wear affects part performance, and characterising the largest needle usable before preform performance suffers, since needle diameter currently limits how thick a preform can be stitched. It also points to using TFP preforms as local reinforcement at bearing and complex loading areas, and to topology optimisation through tow steering.

Funding and partners

The work was funded in part by the Office of Energy Efficiency and Renewable Energy, U.S. Department of Energy, under Award DE-EE0006926. The authors acknowledge financial support from IACMI, JobsOhio, Airbus Americas Inc., Lockheed Martin Corporation and ZSK, and technical help from Michigan State University. IACMI is managed by Collaborative Composite Solutions, Inc.

The report carries the standard federal disclaimer: the information was funded in part by an agency of the United States Government, which makes no warranty as to its accuracy or completeness, and the views of the authors do not necessarily reflect those of the United States Government.