STRESS DISTIBUTION, FAILURE PHENOMENON AND ENHANCING MECHANICAL INTEGRITY STUDY ON ADHESIVE JOINT COMPOSITE PIPE UNDER INTERNAL PRESSURE AND TORSIONAL LOAD

• Main Author: Akmal, Jamiatul
• Format: Dissertations
• Language: Indonesia
• Subjects: Teknik (Rekayasa, enjinering dan kegiatan berkaitan)
• Online Access: https://digilib.itb.ac.id/gdl/view/41438
• Institution: Institut Teknologi Bandung

Composite pipes have been known and used since the last 40 years. This pipe is generally used as an alternative while a steel pipe having high corrosion rate resulting in uneconomic and could harm the environment. The advantages of composite pipe not only in terms of resistance to corrosion, but also lighter and stronger if the direction of the fiber is designed optimally match the orientation of the principal stress. One of the problems in using composite pipe is the limited connection method and often leak. This research studied one type of connection commonly used, namely adhesive joint. Adhesive joint problems is the high stress concentration at the edges of joint. This stress concentration can initiate a connection failure and ineffective. Some researchers have proposed modifications to eliminate this problem, such as proposed several models: The taper joint and the taper / taper joint. These methods were considered not satisfactory because the failure was initiated from the edge of the connection. The purpose of this study is to get an optimum design with better integrity. To achieve these goals, the first step is the study of the characteristics of adhesive joint. The study begins with an analysis of the stress distribution in the adhesive layer, pipe and coupler. Further parametric study to determine the effect of the thickness of the adhesive layer, the length of the connection, the ratio of adhesive elasticity to the pipe elasticity and ratio of coupler thickness to pipe thickness. These parameters are then varied by numerical simulations to get a new design with minimum of stress concentration. In this study proposed two new methods for adhesive joint is relatively different from the previous models. The first model, called the model tirus-dalam, is a model which is tapered inside the coupler. This method has the dual effects, which decrease the stress concentration is not only due to the reduction coupler cross-section, but at the same time as a thickening layer of adhesive. This model is more effective than taper joint models, the proposed model of previous researchers. This model can reduce the stress concentration to 1.4, approximately 56.25% lower than 3.2 the stress concentration at the joint taper models. The second model, called the model dua-adesif. This model uses two kinds of adhesive material. Low elasticity adhesive used on the edges and high elasticity adhesive used in the middle of the connection. From the numerical analysis it is known that this model can reduce the stress concentration 18.75%, when compared to models that use only one type of adhesive. The study is completed by an experimental study by making a number of specimens. Stress distribution in adhesive layer was measured with a strain gauge. Furthermore, the specimen is subjected to torque and internal pressure. Stress distribution at the adhesive layer can be known from the electrical potential generated by each sensor. Electrical potential read by the reader apparatus data (data acquisition). Experimental studies were conducted to validate theoretical and numerical studies have been done. The results of the stress distribution measurement on five specimens with the load torque showed the same trends with theoretical and numerical studies, despite differences in measurement results. Significant differences occurred in the specimen-2 with an error of about 20% at position x / L = 0 and 17% at position x / L = 1. From the test specimen to the internal pressure loads also showed the same trend, although an error of about 20% at position x / L = 1. The experimental study is also intended to observe the phenomenon of failure. Testing internal pressure for a model without modification shows that the failure mode is generally in the form of leakage. The leak occurred at the boundary surface between the adhesive material to the surface of the pipe / cuopler (adhesive failure mode). From the observation of the cross-piece specimen shows that the failure started from the edge (x / L = 0). Two models proposed, model tirus dalam be successfully overcome leakage. Of the three specimens tested, two specimens (specimens TD-2 and TD-3) did not leak until the internal pressure of 700 psi (? 4.8 MPa, the maximum limit of the test equipment). Only one specimen (specimen TD-1) that a leak in the pressure of ? 400 psi (? 2.76 MPa). Leaks in the TD-1 specimen due its low production quality. In the cross-sectional specimen pieces visible porosity and lack of resin.