Structural Materials
Pre-Recorded Presentations
Cole Cappon
Graduate Student
Title: Composite Creep Tests
Email: capponct@clarkson.edu
Department of Mechanical Engineering
Advisor: Craig Merrett
Abstract: Material creep is the process of materials like polymer composites or metals at high temperatures to slowly deform under a constant load or stress. Understanding the long-term material effects in a structure is essential to building precision components. Obtaining creep data requires the use of specialized testing rigs that maintain a constant stress / load on test specimens. For our experiments, 8 custom dead weight creep rigs were designed and built. These rigs utilize ASTM D638 Type-I specimens made from Poly(methyl methacrylate) (PMMA) and a high precision IL-030 laser to measure the distance the specimens deform over the duration of each experiment. Testing was performed at 23±2 °C and 50±10 %RH. Specimen dimensions were measured using a digital caliper. The specimens were loaded in uniaxial tension at a monotonic stress to reach their goal experiment duration. ASTM outlines that creep experiments must fall into 7 duration time periods (1, 10, 30, 100, 300, 1000 & 3000 hours). The prescribed stress was then held constant and the displacement was recorded until the specimen fractured. The displacement recorded, specimen dimensions and applied stress are used in data processing to calculate the strain over time for each experiment. This strain data is then processed into creep compliance that enables fitting of a Prony series to the experimental data to establish an analytical solution of the long-term effects of a polymer under loading.
Sandeep Khadka
Graduate Student
Title: Microstructural and Nanomechanical Properties Characterization of AlCuFeNiTi High Entropy Alloy Manufactured by Direct Energy Deposition
Department of Mechanical and Aeronautical Engineering
Email: khadka@clarkson.edu
Advisor: Philip Yuya
Abstract: High entropy alloys (HEAs) provides an interesting research direction towards developing novel metallic materials for many applications. An HEA is a simple-phase solid solution alloy with four or more principle components in equimolar or near equimolar rations. Because of their unique mutielement composition, HEAs exhibit a number of very interesting and useful properties such as high strength, low temperature toughness, and high irradiation resistance. In this work, an equiatomic AlCuFeNiTi high entropy alloy was manufactured using pre-alloyed powder on the Ti6Al4V substrate by direct energy deposition (DED). Its microstructure and mechanical properties were investigated using scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS) and nanoindentation. SEM and EDS were performed to study the structure and composition of the alloy and nanoindentation was done to determine the hardness and reduced modulus of the alloy.
Kimberly Konar
Undergraduate Student
Title: Development of a Distributed Sensing Fiber Optic App for Principal Strain Calculations
Department of Mechanical and Aeronautical Engineering
Email: konarke@clarkson.edu
Advisor: Marcias Martinez
Abstract: The concept of structural health monitoring, in-situ load monitoring and damage detection of aircraft structures, was created to reduce the cost of operation and increase the aircraft lifecycle while maintaining safety. Currently, load monitoring is challenging because traditional strain gauges only take measurements at one location and have bulky wires attached to them. Fiber optic sensors (FOS) are a possible alternative in this application because they are flexible and take multiple measurements along the fiber length. One problem with using FOS is that the fibers are fragile, causing them to break when bent in a tight radius. This can be mitigated by applying protective sleeves to the weak junctions along the sensor, in addition to ensuring a sufficiently large radius during the installation of the fiber on the structure. The data collected from FOS is extensive, requiring computational software that can handle large data sets. The objective of this research is to establish an application (App) that allows users to obtain data from a FOS in uniaxial, biaxial, and triaxial orientations in order to generate graphs and compute material properties that are useful for Finite Element Analysis verification. Principal strain is the focus of the biaxial and triaxial calculations, as users will be able to understand material behavior. To verify that the App is running correctly, tensile tests were performed utilizing FOS and traditional strain gauges. Material properties were calculated from the strain gauge data using Excel to compare to the FOS results from the App. The Federal Aviation Administration (FAA), through a collaboration agreement (CRADA) between Prof. Martinez and the FAA, are interested in the use of this type of App for their full-scale tests. This would allow them to make use of FOS as a replacement to commonly used strain gauges that run the risk of fatiguing during their tests, thus drifting and providing erroneous measurements in critical regions of the structure.