Sandwich structures with synthetic and natural fiber composite skins under flexural and axial loading
Bibliographic record
Abstract
This paper is an overview of research activities at Queen's University, Canada, over the past ten years, pertaining to sandwich panels with both glass fiber reinforced polymer (GFRP) and flax-FRP (FFRP) skins.The research addressed flexural performance and behavior under axial compression loading, including slenderness effect.Both short and long term behaviors, including fatigue performance [1,2] and durability under thermal cycles and in salt solution [3], have been studied.The effects of core density [4][5][6], skin-to-core thickness ratio, particularly with FFRP skins [7,8], and internal rib configuration [9,10] were explored, followed by a full scale test on cladding wall panel under air pressure [11].The effect of reversed bending fatigue representing wind pressure and suction was studied [12].The experimental work was complemented by analytical and numerical investigations accounting for both material and geometric nonlinearity arising from the soft core [13][14][15][16].The research showed that sandwich panels with FFRP skins can indeed provide equivalent flexural and axial strength to panels with GFRP skins; however, thicker skins by about 20% are necessary.Tensile strength and modulus of FFRP are sensitive to number of layers.As the layers increased from one to five, the properties also increased but plateaued at three layers.Vacuum bag (VB) molding resulted in an apparent increase in tensile strength of FFRP coupons; however, when applied to sandwich panels there is a decrease in ultimate load of the panel of up to 27%, compare to wet layup (WL) because the VB thinner skins are more susceptible to skin wrinkling.VB specimens also demonstrated a higher susceptibility to environmental degradation than WL specimens.Tensile strength retentions of FFRP are better than GFRP at elevated temperatures.The 300 days retentions of FFRP at 23 o C, 40 o C, and 55 o C were 81, 76 and 72%, while for GFRP were 86, 72 and 61%, respectively.Fatigue threshold of panels without ribs was 37% of the ultimate static capacity.In order for panels to sustain at least two million cycles, load should be limited to about 45% of the static capacity (and 30% for fully reversed bending).The benefit of ribs was more significant in low cycle fatigue (from zero to approximately 1,000 cycles).From 1,000 cycles to infinite fatigue life (high cycle fatigue), the contribution of ribs to strength reduced gradually to zero.Increasing core density from 32 to 96 kg/m 3 , increased axial strength of panels by 116-176% at various slenderness ratios.
Fetched live from OpenAlex and de-inverted. Abstracts are not stored in this database: the inverted indexes are 8.6 GB of the frame’s 9.3 GB of text, and the host has 13 GB free.
How this classification was reachedexpand
Full frame distilled prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. Learned from the 10,348 direct Codex labels and 10,348 direct Gemma labels. Candidate is the union of thresholded teacher heads; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels or direct frontier model labels.
Codex and Gemma teacher scores by category
| 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 | 0.002 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.000 | 0.000 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.000 | 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 teacher head, 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".