In this study, a work-of-fracture method using a three-point bend beam (3PBB) specimen, which is commonly used to determine the fracture energy of concrete, was adapted to evaluate the mode-Ⅰ fracture and durability of fiber-reinforced polymer (FRP) composite-concrete bonded interfaces. Interface fracture properties were evaluated with established data reduction procedures. The proposed test method is primarily for use in evaluating the effects of freeze-thaw (F-T) and wet-dry (W-D) cycles that are the accelerated aging protocols on the mode-Ⅰ fracture of carbon FRP-concrete bonded interfaces. The results of the mode-Ⅰ fracture tests of F-T and W-D cycle-conditioned specimens show that both the critical load and fracture energy decrease as the number of cycles increases, and their degradation pattern has a nearly linear relationship with the number of cycles. However, compared with the effect of the F-T cycles, the critical load and fracture energy degrade at a slower rate with W-D cycles, which suggests that F-T cyclic conditioning causes more deterioration of carbon fiber-reinforced polymer (CFRP)-concrete bonded interface. After 50 and 100 conditioning cycles, scaling of concrete was observed in all the specimens subjected to F-T cycles, but not in those subjected to W-D cycles. The examination of interface fracture surfaces along the bonded interfaces with varying numbers of F-T and W-D conditioning cycles shows that (1) cohesive failure of CFRP composites is not observed in all fractured surfaces; (2) for the control specimens that have not been exposed to any conditioning cycles, the majority of interface failure is a result of cohesive fracture of concrete (peeling of concrete from the concrete substrate), which means that the cracks mostly propagate within the concrete; and (3) as the number of F-T or W-D conditioning cycles increases, adhesive failure along the interface begins to emerge and gradually increases. It is thus concluded that the fracture properties (i.e., the critical load and fracture energy) of the bonded interface are controlled primarily by the concrete cohesive fracture before conditioning and by the adhesive interface fracture after many cycles of F-T or W-D conditioning. As demonstrated in this study, a test method using 3PBB specimens combined with a fictitious crack model and experimental conditioning protocols for durability can be used as an effective qualification method to test new hybrid material interface bonds and to evaluate durability-related effects on the interfaces. 相似文献
Knee cartilage damage is a common cause of referral for orthopedic surgery. Treatment aims to reduce pain and symptoms by repairing cartilage. Microfracture, the current standard of care, yields good short-term clinical outcomes; however, treatment might fail after 2–3 years. A Chitosan-Beta glycerolphosphate-based medical device (BST-CarGel) is used as an adjunct to microfracture and demonstrates improvements in quantity and quality of repaired tissue, potentially reducing the risk of treatment failure. This study aimed to establish the economic value of BST-CarGel vs microfracture alone in knee cartilage repair from the societal perspective, using Germany as the reference market.
Methods:
A decision tree with a 20-year time-horizon was constructed, in which undesirable clinical events were inferred following initial surgery. These events consisted of pain management, surgery, and total knee replacement. Clinical outcomes were taken from the pivotal clinical trial, supplemented by other literature. Data and assumptions were validated by a Delphi panel. All relevant resource use and costs for procedures and events were considered.
Results:
In a group of patients with all lesion sizes, the model inferred that BST-CarGel yields a positive return on investment at year 4 (with 20-year cumulative cost savings of €6448). Reducing the incremental risk of treatment failure gap between the device and microfracture by 25–50% does not alter this conclusion. Cost savings are greatest for patients with large lesions; results for patients with small lesions are more modest.
Limitations:
Clinical evidence for microfracture and other interventions varies in quality. Comparative long-term data are lacking. The comparison is limited to microfracture and looks only at costs without considering quality-of-life.
Conclusion:
BST-CarGel potentially represents a cost-saving alternative for patients with knee cartilage injury by reducing the risk of clinical events through regeneration of chondral tissue with hyaline characteristics. Since the burden of this condition is high, both to the patient and society, an effective and economically viable alternative is of importance. 相似文献
