The evolution of alternative materials and techniques for structural rehabilitation is of essential importance to the preservation of existing reinforced concrete (RC) and masonry structures. Fabric Reinforced Cementitious Matrix (FRCM) composite systems represent a suitable repair methodology for structural strengthening. To this purpose, a research program is undertaken to investigate their interlaminar shear characteristics. The current test method ASTM D2344 "Standard Test Method for Short-Beam Strength of Polymer Matrix Composite Materials and Their Laminates", because of the complexity of internal stresses in the specimen loaded under three-point bending, makes it difficult to relate the short-beam strength to any one material property. Although shear is the dominant applied loading at the fabric-mortar interface in this test method, a variety of failure modes can occur. To date, FRCM specimens tested demonstrate a flexural or matrix diagonal tension failure which does not exactly address interlaminar properties. This work aims to investigate new specimen designs targeted at characterizing the interlaminar shear behavior. After an introductory section covering composite materials for structural applications and a review of the Short-Beam Shear test, the first study focuses on demonstrating why the current test method is inadequate for examining the interlaminar shear strength of FRCM systems. The second study concentrates on exploring varying specimen geometries, different number of layers, and new test configurations in order to identify a methodology which is reliable and consistent for studying FRCM interlaminar shear behavior. The objective of these two studies is to improve AC434 "Acceptance Criteria for Masonry and Concrete Strengthening Using Fiber-reinforced Cementitious Matrix (FRCM) Composite Systems" including recommendations to characterize the interlaminar shear performance of FRCM systems. The results of this modified test method can be used for quality control for material selection by manufacturers. Moreover, to confirm that the test method developed in the previous studies is actually the most suitable way to investigate the interlaminar shear behavior of FRCM systems another test methodology is evaluated. An additional study addresses a durability analysis for 1000-hour exposure aimed at examining the FRCM specimen behavior under the SBS test subject to aggressive environmental conditions. The goal is to evaluate the environmental durability tests presented in AC434 in order to characterize the FRCM reaction to the proposed conditions.
L’evoluzione di materiali e tecniche alternative per la riabilitazione strutturale è di essenziale importanza per la preservazione di strutture esistenti in calcestruzzo armato e muratura. I sistemi compositi FRCM rappresentano un eccellente metodo di rinforzo strutturale. Il progetto di ricerca nasce con lo scopo di indagare il comportamento interlaminare a taglio di materiali compositi con matrice cementizia. Il test proposto per tale ricerca è lo standard ASTM D2344 "Standard Test Method for Short-Beam Strength of Polymer Matrix Composite Materials and Their Laminates" e in molti casi, a causa della complessità delle tensioni interne nel provino, è difficile relazionare la forza delle Short-Beam ad una specifica proprietà del materiale. Sebbene il taglio è il carico dominante all’interfaccia tessuto-malta in questo tipo di test, possono avvenire una varietà di modi di rottura. Fino ad oggi, tutti i campioni FRCM testati mostrano una rottura per flessione o per tensione diagonale della matrice cementizia che non riguarda esattamente le proprietà interlaminari. Questo lavoro ha lo scopo di indagare nuove geometrie e configurazioni di campioni volte a caratterizzare il comportamento interlaminare a taglio. Dopo una panoramica introduttiva dei materiali compositi ed una revisione dello Short-Beam Shear test, il primo studio dimostra il motivo per cui il test proposto è inadeguato per esaminare la resistenza a taglio interlaminare di sistemi FRCM. Il secondo studio indaga nuove geometrie, differenti numeri di layers e nuove configurazioni di test al fine di individuare una metodologia che sia affidabile e coerente per lo studio del comportamento interlaminare a taglio del composito FRCM. L’obiettivo di questi due studi è quello di migliorare la norma AC434 "Acceptance Criteria for Masonry and Concrete Strengthening Using Fiber-reinforced Cementitious Matrix (FRCM) Composite Systems" introducendo raccomandazioni per caratterizzare la resistenza interlaminare dei sistemi FRCM. I risultati di questa nuova metodologia di test possono essere utilizzati ai fini di controllo qualità per la scelta del materiale da parte dei produttori. Inoltre, per dimostrare che il metodo sviluppato negli studi precedenti è realmente il modo più adatto per studiare il comportamento interlaminare a taglio di sistemi FRCM viene valutata un’altra tipologia di test. Un ulteriore studio affronta un'analisi della durabilità per 1000 ore di esposizione volta ad esaminare la risposta dell’FRCM soggetto a diverse condizioni ambientali aggressive. Questo lavoro ha lo scopo di valutare i test sulla durabilità ambientale proposti nella norma AC434 al fine di caratterizzare la reazione dell’FRCM alle condizioni proposte.
Investigation of interlaminar shear behavior of fabric reinforced cementitious matrix (FRCM) composite systems
MONTESI, MICHELE
2014/2015
Abstract
The evolution of alternative materials and techniques for structural rehabilitation is of essential importance to the preservation of existing reinforced concrete (RC) and masonry structures. Fabric Reinforced Cementitious Matrix (FRCM) composite systems represent a suitable repair methodology for structural strengthening. To this purpose, a research program is undertaken to investigate their interlaminar shear characteristics. The current test method ASTM D2344 "Standard Test Method for Short-Beam Strength of Polymer Matrix Composite Materials and Their Laminates", because of the complexity of internal stresses in the specimen loaded under three-point bending, makes it difficult to relate the short-beam strength to any one material property. Although shear is the dominant applied loading at the fabric-mortar interface in this test method, a variety of failure modes can occur. To date, FRCM specimens tested demonstrate a flexural or matrix diagonal tension failure which does not exactly address interlaminar properties. This work aims to investigate new specimen designs targeted at characterizing the interlaminar shear behavior. After an introductory section covering composite materials for structural applications and a review of the Short-Beam Shear test, the first study focuses on demonstrating why the current test method is inadequate for examining the interlaminar shear strength of FRCM systems. The second study concentrates on exploring varying specimen geometries, different number of layers, and new test configurations in order to identify a methodology which is reliable and consistent for studying FRCM interlaminar shear behavior. The objective of these two studies is to improve AC434 "Acceptance Criteria for Masonry and Concrete Strengthening Using Fiber-reinforced Cementitious Matrix (FRCM) Composite Systems" including recommendations to characterize the interlaminar shear performance of FRCM systems. The results of this modified test method can be used for quality control for material selection by manufacturers. Moreover, to confirm that the test method developed in the previous studies is actually the most suitable way to investigate the interlaminar shear behavior of FRCM systems another test methodology is evaluated. An additional study addresses a durability analysis for 1000-hour exposure aimed at examining the FRCM specimen behavior under the SBS test subject to aggressive environmental conditions. The goal is to evaluate the environmental durability tests presented in AC434 in order to characterize the FRCM reaction to the proposed conditions.| File | Dimensione | Formato | |
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https://hdl.handle.net/10589/112102