Adhesively bonded joints are used extensively in various industries. Some imperfections like holes, thermal residual stresses occurring in the bolted, welded, riveted, and soldered joints don't take place in adhesively bonded joints. Hence, the main advantages of bonded joint are lightness, sealing, corrosion resistance, heat and sound isolation, damping, and quickly mounting facility which have been highly proved. This paper introduces an attempt to study the dynamic analysis of adhesively bonded joint for composite structures to investigate mainly the influences of lamina code number, bonded adhesive line configuration and boundary condition on the dynamic behavior of the test specimens containing composite assembly. The numerical based on the use of finite element model (FEM) modified by introducing unified mechanical properties are represented and applied to compute efficiently the Eigen-nature for composite bonded structures. The experimental tests are conducted to investigate such adhesive bonded joints using two different techniques. The first technique includes an ultrasonic technique in which the magnetostractive pulse echo delay-line for material characterization of composite material is used. The second technique is bassed on the use of the frequency response function method (FRF) applying the hammering method. The comparison between the numerical and experimental results proves that the suggested finite element models of the composite structural beams with bonded joints provide an efficient by accurate tool for the dynamic analysis of adhesive bonded joints. The damping capacity is inversely proportional to the stiffness of the bonded joint specimens. The type of the proportionality depends mainly on the bond line configuration type, lamina orientation, and boundary conditions. This in turn enables an accurate evaluation for selecting the proper characteristics of the specimens for controlling the present damping capacity and the proper resistance against deformation during the operating process. The present study provides an efficient non-destructive technique for the prediction of dynamic properties for an adhesive bonded joint for the studied composite structure systems. The coordination of the experimental and numerical techniques makes it possible to find an efficient tool for studying the dynamic performance of adhesively bonded joint for composite structures.

This paper is concerned with the dynamic analysis of a rotating composite shaft. The numerical finite element technique is utilized to compute the eigen pairs of laminated composite shafts. A finite element model has been developed to formulate the stiffness matrices using lamination theory. These matrices take into account the effects of axial, flexural and rotating on the eigen-nature of rotating composite shaft. The Campbell diagram is utilized to compute the critical speed of rotating composite shaft and instability regions to achieve accuracy and for controlling the dynamic behavior of the system in resonance state. The influence of laminate parameters: stacking sequences, fiber orientation, boundary conditions and fiber volume fractions effect on natural frequencies and instability thresholds of the shaft are studied. The results are compared to those obtained by using the finite element method and experimental measurements using frequency response function method (FRF) by applying the autogenously excitation "from self excitation due to driving motor". In the experimental part, the response of composite shaft with various types of boundary conditions and five lamina orientations were recorded and analyzed by utilizing fast Fourier transform dual channel analyzer in conjunction with the computer. The comparison between the numerical and experimental results proves that the suggested finite element models of the composite shaft provide an efficient accurate tool for the dynamic analysis of rotating composite shaft.

Unsaturated polyester-based composites and reinforced with three types of fabrics, E-glass, basalt, and carbon, were fabricated by Hand-Lay Up (HLU) technique at room temperature, with various fiber configuration. Monotonic mechanical properties of hybrid composites laminate such as the tensile, flexural, inter-laminer shear strength and impact strength were investigated. The dynamic response of hybrid laminates composite under pulse load was studied theoretically and experimentally. In the theoretical part, the validity of the theoretical model for evaluating natural frequencies, mode shapes and dynamic response of hybrid composite laminates at various staking sequence has been examined by utilizing of the finite element software (ANSYS). In the experimental part, the response of hybrid composite specimens with various types of fiber configuration and four types of boundary fixations was measured by hammer test technique "frequency response function" (FRF). The results show that the reinforcement by adding the basalt fabric and carbon fabric based unsaturated polyester composites as a fiber configuration [2C/B/2C] S enhanced the mechanical properties of the hybrid composite laminates among other various stacking sequences. For the stacking sequence [2C/B/2C] S , it was found that the largest values of tensile, flexural strength and interlaminar shear strength (ILSS) were 128.76 MPa, 405 MPa, 20.25 MPa, respectively. The results show the good bonding adhesion at the interface between the fibers and matrix of the hybrid composite laminates. The impact properties with stacking sequences [C-C-G-C-C]s have the largest value at 3.73 Joule as compared with the other composites and stacking sequences of all hybrid composite laminates. Also, the BFRP composites specimen gives the best vibration resistance compared to the other stacking sequences of hybrid composite laminates. The comparison between experimental and numerical model shows the efficiency of the proposed mathematical model of the composite structural specimen with bonded joints.

The present study investigates the friction stir processing (FSP) effect on the mechanical and dynamic response of AA5052-H32.FSP was applied on a 1.5 mm thick aluminium sheet at three rotational speeds (495 rpm, 850 rpm, 1660 rpm) and two longitudinal feed rates (24 mm/min, 42 mm/min). The processed samples were mechanically tested by tensile and micro-hardness tests. The macrostructure of the FSPed zone was also investigated. The highest detected ultimate tensile strength (207.5 MPa) was observed at 850 rpm and 42 mm/min. The FSPed conditions 1660 rpm and 24 mm/min provide the highest mean value of micro-hardness (66.57 HV) at lowest standard deviation (SD). The macrostructure showed the successful stirring process. The dynamic behavior was investigated at the processed conditions by applying free vibration analysis at different sets of boundary conditions. By introducing unified mechanical parameters, the mathematical finite element analysis (FEA) is efficient in computing the Eigen-nature of FSP. The experimental analysis was carried out using frequency response function (FRF) using hammering method. The comparison between experimental and numerical models showed the efficiency of the proposed mathematical model for the FSP. The change of rotational speed from 495 rpm to 850 rpm increases the fundamental natural frequency by 7.11%, while the change from 850 rpm to 1660 rpm decreases it by 13.1%. The change of boundary fixation from C-C to C-F decreases the fundamental natural frequency by an average of 40.22%.The highest damping factor was occurred at 1600 rpm, 42 mm/min, and C-F boundary fixation.