| Tubular structures fabricated from composite materials are used in many applications because of their light weight and high strength and stiffness. In aerospace applications they are used for advance aircraft fuselages, rocket motor cases, large space telescopes, space station truss structures, landing gear and launch tubes. Their use as suspension components and drive shafts in automotive applications are also very popular.; The major manufacturing techniques available for composite tube fabrication are filament winding, lamination and preform consolidated by resin transfer molding process (RTM). The most advantageous of these methods which has now attracted a great deal of research is RTM. The basic reasons why this method is most acceptable are low capital equipment cost, low injection pressure, excellent surface finish, low labor, low parts cost, and reduced styrene emissions. The ability to vary the level, type and orientation of reinforcement, mold complex shapes and the possibility of including encapsulated cores, ribs and inserts into the part are also some of the advantages of RTM process.; Previous RTM methods for fabricating composite tubes have utilized a two part mold (split mold), which has resulted in formation of undesirable seams in the final product. In this experiment an RTM technique was developed to fabricate a seamless tube using a single mold and Teflon{dollar}spcircler{dollar} rod mandrel.; The presence of voids in a composite material has an adverse effect on the mechanical properties. Their presence in the matrix is particularly detrimental to matrix-dominated properties (such as interlaminar shear strength, compressive strength, and fatigue life).; The void content of fabricated tubes were determined using a Sonotek Ultrasonic C-Scan which utilizes a pulse-echo method. This machine was originally capable of scanning flat panels, however a fixture unit was designed that made it adaptable for tube scanning. The fiber volume fraction of fabricated tubes were determined using the acid digestion method and specific gravity by water displacement technique.; The prediction of the elastic properties of reinforced composites using different micromechanics theories have evolved in recent years. The analytical model used in these predictions often involve mathematical complexity ranging from simple netting analysis to sophisticated statistical methods, with the ultimate aim of predicting the failure properties and performance of these structures.; A Fabric Geometry Model (FGM) was utilized to predict the elastic constants of the fabricated biaxial and triaxial braided composite tubes. Predicted values were fairly close to experimental results.; In practical applications, composite tubes are subjected to various loading conditions such as axial, torsion, bending and internal pressurization or a combination of these loads.; An experimental study was conducted on the fabricated tubes by subjecting them to axial, torsion and combined axial-torsion loading, using an MTS axial/torsion testing machine. A failure envelope was developed from the experimental data obtained. |
