Sandwich structures with synthetic and natural fiber composite skins under flexural and axial loading
Notice bibliographique
Résumé
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.
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Prédiction distillée sur la base complète
Imitation des enseignantsNi prévalence calibrée, ni vérité terrain. Validation humaine à venir. Apprise à partir de 10 348 étiquettes directes de Codex et de 10 348 étiquettes directes de Gemma. Le mode candidate est l'union des têtes enseignantes seuillées; le consensus est leur intersection. Ces sorties portent le statut machine_predicted_unvalidated et ne sont ni des étiquettes humaines ni des étiquettes directes de modèles de pointe.
Scores Codex et Gemma par catégorie
| Catégorie | Codex | Gemma |
|---|---|---|
| Métarecherche | 0,000 | 0,000 |
| Méta-épidémiologie (sens strict) | 0,000 | 0,000 |
| Méta-épidémiologie (sens large) | 0,000 | 0,000 |
| Bibliométrie | 0,000 | 0,000 |
| Études des sciences et des technologies | 0,000 | 0,002 |
| Communication savante | 0,000 | 0,000 |
| Science ouverte | 0,000 | 0,000 |
| Intégrité de la recherche | 0,000 | 0,000 |
| Charge utile insuffisante (le modèle a refusé de juger) | 0,000 | 0,000 |
Scores machine (provisoires)
Les deux têtes enseignantes du modèle étudiant, lues sur ce travail. Un score ordonne la base pour la relecture; il n'affirme jamais une catégorie, et le statut de validation accompagne chaque rangée tel quel.
Scores de référence d'un modèle non mature (critères de maturité non atteints, 7 itérations). Un score ordonne; il n'affirme jamais une catégorie.
score_only:v0-immature-baseline · tel quel depuis la passe de notation : score_only signifie que le nombre peut ordonner les travaux, et qu'aucune étiquette de catégorie n'en découleClassification
machine, non validéePrédiction automatique; un appel candidat d’une seule tête enseignante, pas un consensus.
Le détail, modèle par modèle et score par score, se trouve en fin de page sous « Comment cette classification a été obtenue ».