Fiber reinforced composite structures are widely used in the aerospace, aircraft, civil and automotive applications due to their high strength-to-weight and stiffness-to-weight ratios and these applications require joining composite either to composite or to metal. There are three main methods for joining composite structures namely, bonding, mechanically fastened or a combination of the two. Bolted joint are preferred in structures where the disassembly is required for the purpose of maintenance and repair. Due to the stress concentration around the holes, bolted joints often represents the weakest part in the structure, and therefore it is important to design them safely. A review on the study of bolted joints in fiber reinforced composite structure is presented. It was found that the behavior of bolted joints in composite structure is affected by many factors, such as geometry, joint material, clamping–load provided by the bolts, ply orientations, etc. Accordingly, various researches have been conducted on the analyses of stress distribution, failure prediction, and strength properties of bolted joint both experimentally and numerically. Accurate prediction of stresses in bolted joints is essential for reliable design of the whole structure; if it is not optimally designed, premature and unexpected failures may be occurred.

The use of defense hole system allows the flow of the stresses to be redistributed by introducing auxiliary holes in the low stress area near the main hole. However, the question remains on the optimal configuration of the defense hole system for effective stress mitigation at the bolt-hole region and, hence, increasing the bearing capacity of particular composite bolted joints. This study presents the influence of defense hole system geometrical design on the stress reduction in a single-bolt, double-lap composite bolted joint. The nonlinear material behavior of the joint was simulated using ANSYS through a progressive failure model, considering the circumferential and radial stresses at bearing, shear-out, and net tension regions of the bolt-hole. It was found that the stress has been reduced between 2.3% and 6.1% for the narrow laminates over a range of E/ D ratios (1–5) with the benefits of the defense hole was clearly marked at DS = 2 D and DHD = 0.75 D. In contrast, for those of wider laminates, the stress reduction ranged from 1.9% to remarkably 18.6%.

No abstract

The creep test is one of the important approaches to determining some mechanical properties of composite materials. This study was carried out to investigate the creep behaviour of an epoxy composite material that was reinforced with Y2O3 powder at weight ratios of 2%, 7%, 12%, 17% and 22%. Each volume ratio was subjected to five loads over the range of 1N to5N at a constant temperature of 16 ± 2°C. In this work, creep behaviour, stress and elasticity modulus were studied through experimental and numerical analyses. Results showed that increasing the weight ratio of Y2O3 powder enhanced creep characteristics.

In this study the effect of casting technique or method of ZA-27 alloy and die angle of equal channel angular extrusion (ECAE) process on the mechanical properties of alloy after forming was studied. Two casting methods, New Rheocast (NRC) and Gravity Die Cast (GDC) were employed to produce the alloy. Four dies of ECAE with different angles (90°, 105°, 120° and 135°) were used in this process at (100° C). Test specimen was manufactured with circular cross section (12mm in diameter and 85mm in length). The results show that the (NRC) method and 90° angle of die in (ECAE) gave the best of compression strength and hardness due to refinement of microstructure more than other angles.The load in (ECAE) process strongly depends on angle of die and specimen product by (NRC) required higher load.