AFP Monocoque Composite Tailboom Full Scale Fatigue Testing
Bibliographic record
Abstract
This paper describes two phases of full scale testing performed on a Bell Helicopter Textron Canada Limited (BHTCL) composite monocoque tailboom manufactured using Automated Fiber Placement (AFP). This technical demonstrator tailboom was designed for use on a Bell 407 model as part of a collaboration program with Bombardier Inc., Composite Atlantic Ltd. and the National Research Council Canada (NRC). The tailboom cone consisted of a skin made from an AFP layup of carbon epoxy fiber tape combined to a hand layup made from fabric. The skin is then bonded to six hand layup frames. The fatigue test objectives were to validate the component to flaw tolerant safe life requirements and establish damage tolerance to light and medium caliber ballistic impacts. The test article, containing embedded flaws, impact damages, and representative repairs, was subjected to a full four lifetime fatigue test at NRC. All testing during this phase was conducted at 250 °F 'hot-dry' conditions to simulate operating temperatures seen in service. The test article successfully sustained four lifetimes of fatigue testing, followed by residual strength testing to both limit and ultimate loads. In the second phase of the full scale testing, the article was subjected to six ballistic impacts with deadweights replicating a critical load condition in the field, interspersed with short 'go-home' fatigue cycling in the laboratory. Regular inspections and near-real-time data analyses were performed throughout testing. No permanent deformation, new damage or existing damage growth was sustained by the tested composite components during the fatigue tests, subsequent residual strength tests, or fatigue loads following ballistic impact, thereby proving the flaw and damage tolerance capability of the structure.
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How this classification was reachedexpand
Full frame machine prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. The Gemma side is a direct model label for every work in the frame, read from the title-only record. The Codex side is a classifier learned from the 10,348 direct Codex labels and calibrated to design-weighted sample rates; fields without enough sample support carry no Codex call. Candidate is the union of the two sides; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels.
Distilled classifier scores by category (both heads)
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.001 | 0.001 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.001 | 0.000 |
| Science and technology studies | 0.000 | 0.000 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.000 | 0.000 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.003 | 0.001 |
Machine scores (provisional)
The two teacher heads of the student model, read on this work. A score orders the frame for review; it never asserts a category, and the validation status ships verbatim with every row.
Baseline scores from an immature model (maturity gate not passed, 7 training rounds). Scores rank; they never assert a category.
score_only:v0-immature-baseline · verbatim from the scoring run: score_only means the number may rank works, and no category label ships from itClassification
machine, unvalidatedMachine predicted; a candidate call from one source (direct Gemma or distilled Codex), not a consensus.
How this classification was reached, model by model and score by score, is at the end of the page under "How this classification was reached".