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Composite lattice structures known as the IsoBeam™ made with unidirectional carbon/epoxy were manufactured and tested in shear-dominated bending. The manufacturing process consisted of placing tows of carbon fiber pre-impregnated with epoxy resin onto a pin-type mandrel to create members with interwoven joints. The members were consolidated with a half spiral aramid sleeve. The IsoBeam structure consists of two main types of members: longitudinal and diagonal members measuring nominally 0.4 in. (10.2 mm) and 0.2 in. (5.1 mm) in diameter, respectively. The hand-manufactured specimens measured nominally 6 in. (152.4 mm) high by 3 in. (76.2 mm) wide by 2 ft (0.61 m) long with 4 bays, each 6 in. (152.4 mm) long. The beams weighed between 1.82-1.86 lbs (8.09-8.27 N). A finite element analysis of the IsoBeam was compared to the experimental results. The IsoBeam specimens were tested in four-point or three-point bending but were dominated by shear due to short-beam bending because of the low length/height aspect ratio. After testing to failure, individual members that were lightly loaded and appeared to be undamaged were removed and tested in axial compression. The void percentage and fiber volume fraction were also measured. The average maximum strength of the IsoBeam structure was 4.11 kips (18.3 kN), yielding an equivalent shear of 2.06 kips (9.15 kN) and bending moment of 20.2 kip-in (2.29 kN-m). This strength was lower than expected and is attributed primarily to low material quality, insufficient consolidation of members, and inadequate tension on the tows during manufacturing. The structure exhibited ductile behavior absorbing considerable energy after initial failure, as well as exhibiting damage tolerance due to the inherent structural redundancy. The inner diagonal members which are inherently stiffer exhibited higher strains than the side outer diagonal members after initial failure. The members removed and tested exhibited an average compression strength of 86.9 ksi (599 MPa) and compression modulus of 17.8 Msi (122 GPa) which are both lower than observed in members tested in past research. The diagonal members had a higher strength of 111 ksi (767 MPa) than the longitudinal member's compression strength of 62.5 ksi (431 MPa). Most members were seen to have a high percentage of voids with an average of 4.3% for diagonal members and 6.4% for longitudinal members. The average fiber volume fraction content of members was very low at 38%. The linear finite element analysis of the IsoBeam structure predicted failure at a load of 34 kips (151 kN). Without considering buckling, the first member predicted to fail was a vertical outer diagonal. This research demonstrates that increasing the manufacturing quality should yield an IsoBeam structure that is strong, ductile and damage tolerant.

The enhancement of node projection techniques in sweeping is the subject of this thesis. Sweeping is a method used to produce all-hexahedral finite element meshes on certain classes of geometry. The placement of nodes in the interior of the geometry during the sweeping process remains a difficult problem. This thesis presents advancements in this area which improve the speed of the algorithm and the resulting element quality. A comparison of existing projection methods was performed. The existing Faceted projection sweeping method was extended to be applicable to more general classes of sweepable geometry. This comparison and extension of node projection algorithms led to the development of a new node projection technique: the SmartAffine method. This method builds on previous techniques and is characterized by its speed. Finally, a technique for coupling node projection techniques is presented. This technique characterizes the complexity of the sweepable geometry and applies the most appropriate node projection scheme. This is accomplished without user interaction and improves the speed of the sweeping algorithm and the quality of swept meshes.

This thesis investigates the suitability of thermo-kinetically recycled plastics for use in commercial product applications using finite element analysis and statistics. Different recycled material blends were tested and evaluated for their use in commercial product applications. There are six different blends of thermo-kinetically recycled plastics used for testing and CATIA is used for finite element analysis. The different types of thermo-kinetically recycled plastics blends are: pop bottles made of PolyethyleneTeraphthalate (PET), milk jugs made of High-Density Polyethylene (HDPE), Vinyl seats made of Poly Vinyl Chloride (PVC) and small amount of Polypropylene (PP) and Urethane, electronic scrap made of engineering resins like Acrylo-Nitrile-Butadiene Styrene (ABS), Polystyrene (PS) and Polycarbonate (PC), agriculture waste consisting of Low Density Polyethylene (LDPE), industrial waste consisting of Nylon (PA66) and PolyethyleneTeraphthalate (PET), household waste consisting of Polystyrene (PS). The methods employed during the study include three phases for each of six blends available: 1.Density, tensile and impact testing of each blend 2.Correlation of mechanical properties to blend 3.Finite element analysis of the service performance of a product made from each thermo-kinetically recycled plastic blend This thesis shows that some of the recycled plastics materials that were tested are qualified to be used in the pallet. Those materials that qualified were Industrial waste consisting of Nylon and PolyethyleneTeraphthalate, household waste consisting of Polystyrene.

Non-uniform rational B-splines (NURBS) methodology is presented, on which the isogeometric analysis is based. T-splines are also introduced as a surface design methodology, which are a generalization of NURBS and permit local refinement. Isogeometric analysis using NURBS and T-splines are applied separately to a structural mechanics problem. The results are compared with the closed-form solution. The desirable performance of isogeometric analysis using T-splines on engineering analysis is demonstrated.

Ductile braced frames are often used to resist lateral earthquake loads in steel buildings; however the presence of a brace element can sometimes interfere with architectural features. One common type of ductile braced frame system sometimes used to accommodate architectural features is the eccentrically braced frame (EBF). In order to dissipate seismic forces, EBF beam regions (called links) must sustain large inelastic deformations. EBF links with column connections must transmit large moments and shear forces to facilitate link rotation. Experiments have shown that welded link-to-column connections tend to fracture in the link flange prior to large link rotations. This study investigated methods for improving EBF link-to-column connection performance, and proposed an alternative ductile braced frame system for accommodating architectural features. Several EBF links with reduced web and flange sections were analytically investigated using validated finite element models in ABAQUS. Results indicated that putting holes in the link web reduced stress and strain values in the link flanges at the connection, but increased the plastic strain and stress triaxiality in the web at the edges of holes. Removing area from the link flanges had little effect on connection stresses and strains. Thus, the reduced web section and reduced flange section methods are not a promising solution to the EBF link-to-column connection problem. The alternative braced frame system proposed in the dissertation used ductile beam splices and buckling-restrained braces in eccentric configurations (BRBF-Es) to accommodate architectural features. Design considerations for the BRBF-Es were determined and dynamic BRBF-E performance was compared with EBF performance. BRBF-E system and component performance was determined using multiple finite element methods. Inter-story drifts and residual drifts for the BRBF-Es were similar to those for EBFs. Results indicated that BRBF-Es are a viable alternative to the EBF, and may result in better design economy than EBFs. With the BRBF-E, damage was isolated within the brace, and in the EBF, damage was isolated within the link, indicating simpler repairs with the BRBF-E. Shop welding of BRBF-E members may replace the multiple field welds required in EBF construction.