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Applied Composite Materials: An International Journal for the Science and Application of Composite Materials (v.11, #4)
A Standard Analysis Methodology for the Stress Analysis of Repaired Aircraft Structures with the Method of Composite Patch Repair by Z. Marioli-Riga; D. Xenos; Chris Vrettos (pp. 191-203).
The method of composite patch repair is a very modern method of repairing damaged aircraft structures, which presents many advantages over the traditional methods of repair. Many analytical as well as numerical methods have been suggested, from time to time, for the stress analysis of such bonded repairs. The engineer (especially one with not very much experience or theoretical background) who will be asked to design a repair may find it difficult to choose the most appropriate method for the specific problem that he has to deal with, among the large number of available analysis methods. The scope of this paper is to suggest a very specific, standardized, step by step analysis methodology for damaged/repaired aircraft structural components.
Keywords: cracked aircraft structures; SIF; FEM software
Use of FRP for RC Frames in Seismic Zones: Part I. Evaluation of FRP Beam-Column Joint Rehabilitation Techniques by A. M. Said; M. L. Nehdi (pp. 205-226).
Multi-storey reinforced concrete frames that were built prior to the 1970's generally do not meet current seismic design code requirements. The lateral load carrying capacity of these structures is often insufficient due to non-ductile reinforcement detailing, which includes either insufficient or no beam-column joint transverse reinforcement. It was observed during recent earthquakes that deficient beam-column joints can jeopardise the integrity of entire structures. Thus, several beam-column joint rehabilitation techniques have emerged to upgrade such substandard joints. It is essential to evaluate the standings of joints rehabilitated with such techniques based on current design code requirements.This paper critically examines beam-column joint rehabilitation techniques using FRP that emerged in the last decade. For this purpose, a full-scale code-conforming beam-column joint was made and tested under reversed cyclic load to serve as a benchmark for this comparison. Enhancements imparted to substandard beam-column joints by FRP rehabilitation techniques in terms of strength, ductility and energy dissipation gains are assessed. It is shown that FRP joints repair schemes generally enhanced the performance of substandard joints, but they often came short of satisfying current standard level performance, and that different rehabilitation strategies can be adopted depending on the type of joint deficiency and the purpose of the rehabilitation scheme.
Keywords: seismic; frames; beam-column joints; FRP; rehabilitation
Use of FRP for RC Frames in Seismic Zones: Part II. Performance of Steel-Free GFRP-Reinforced Beam-Column Joints by A. M. Said; M. L. Nehdi (pp. 227-245).
The use of FRP as reinforcement in concrete structures has been growing rapidly due to its advantages over conventional steel reinforcement (e.g., corrosion resistance, light weight, magnetic neutrality). A potential application of FRP reinforcement is in structural concrete frames. However, current seismic design standards and detailing criteria for beam-column joints were established for steel reinforcement and may be unsuitable for FRP reinforcement due to its different mechanical properties. During recent earthquakes, many structural collapses were initiated or caused by beam-column joint failures. Since there are no detailed specifications for the application of FRP reinforcement in seismic zones, research is needed to gain a better understanding of the behaviour of FRP-reinforced concrete under seismic loading. In this study, two full-scale beam-column joint specimens reinforced with steel and GFRP, respectively, were tested in order to investigate their performance in the event of an earthquake. The control steel-reinforced specimen is detailed according to the Canadian Code (CSA A23.3-94) recommendations. The GFRP-reinforced specimen is detailed in a similar scheme but using a GFRP grid. The behaviour of the two specimens under reversed cyclic loading, their load-storey drift envelope relationship and energy dissipation ability were compared. The GFRP-reinforced specimen showed a predominantly elastic behaviour up to failure. While its energy dissipation was low, its performance was acceptable in terms of total storey drift demand.
Keywords: NEFMAC; grid; GFRP; seismic; beam-column joint; frames
Friction Stir Welding of Ceramic Particle Reinforced Aluminium Based Metal Matrix Composites by P. Cavaliere; E. Cerri; L. Marzoli; J. Dos Santos (pp. 247-258).
The mechanical and microstructural properties of 6061+20% Al2O3p and 7005+10% Al2O3p aluminium based metal matrix composites joined by friction stir welding were analyzed in the present study. The two materials were welded into the form of sheets of 7 mm thickness after T6 treatment and were tested in tension at room temperature. The microstructure of the joints was observed by optical microscopy and the fracture surfaces were analyzed by employing a scanning electron microscope equipped with field emission gun in order to study the micromechanisms involved during the deformation.
Keywords: MMCs; friction stir welding; FEGSEM