Flexural Behavior of Sandwich Panels with Bio-FRP Skins Made of Flax Fibers and Epoxidized Pine-Oil Resin
Bibliographic record
Abstract
Structural sandwich panels with fiber-reinforced polymer (FRP) skins are becoming an increasingly popular system because of their remarkable light weight, ease and speed of installation, and high thermal insulation capabilities. This paper looks into the potential for replacing conventional glass fiber–reinforced polymer (GFRP) skins with bio-based skins made of unidirectional flax fibers and a resin blend consisting of epoxidized pine oil. A comprehensive material testing program was first carried out on 70 standard tension and compression coupons. Then, 36 sandwich panels of 1,000×150×75 mm were tested under four-point loading. The number of flax fiber–reinforced polymer layers of skin was varied from one to five [in comparison to one layer of GFRP, an epoxidized pine oil resin blend to epoxy, and the wet layup (WL) fabrication method to vacuum bag molding]. Sandwich panels with three layers of flax fibers provided equivalent strength and stiffness, but better deformability, compared to panels with one layer of glass fibers. Epoxidized pine oil-based skins decreased strength by up to 23% compared to epoxy-based skins. Vacuum-bagged panels decreased strength by up to 27% compared to WL as a result of thinner skins. As the number of flax layers increased from one to five, failure modes transitioned from skin wrinkling in the constant moment region to core shear failure or compression skin crushing in the shear span.
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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 | 0.000 |
| 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".