The Effect of Viscoelasticity on the Life Expectancy of Light Composite Aircraft
Bibliographic record
Abstract
In modern aircraft, polymer matrix composites (PMC) are becoming more prevalent in both primary and secondary structures due to their high strength and stiffness to weight ratios.Due to the molecular composition of polymers, these materials exhibit viscoelastic phenomena such as creep, recovery and relaxation.The scope of this thesis is to predict the service life of the Diamond DA-20 Katana based on the viscoelastic properties of the MSG L285/H287 epoxy matrix.The prediction methodology is applied to the composite wing spar because the spar bears the majority of the load during flight.The methodology requires the experimental characterization of the epoxy matrix, which was achieved by retrofitting a decommissioned undergraduate laboratory furnace.The retrofit created a novel creep and relaxation measurement apparatus.Using elevated temperature, the long term response of the epoxy matrix was determined using the time-temperature superposition principle.The results were then applied to the spar to determine its long term response using the Classical Lamination Theory applied to complex geometries.Failure was determined based on the Tsai-Hill and maximum strain failure theory or if the compressive flange buckles under the applied load.Based on the analysis, it was determined that the MSG L285/H287 epoxy system adheres to the Time-Temperature Superposition principal and master curves were generated using a limited data set.Composite analysis was performed on the wing spar using the viscoelastic properties of the epoxy.Based on the analysis presented in this thesis, it is concluded that Diamond's claim's of unlimited service life is possible based on the assumptions made with respect to viscoelastic phenomena. Common Subscript fFibre properties g Glass temperature iVariable number m Matrix properties o Initial conditions kComposite ply number w, tf, bf Components of I-beam -web, top and bottom flange x, y, zGlobal frame of reference 1, 2, 3 Local frame of reference xiii
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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 | 0.000 | 0.001 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.000 | 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) | 0.001 | 0.000 |
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".