BS in Mechanical Engineering
Mechanical Engineering Department
Workstation tables in commuter rail trains have been identified as an area for improving passenger safety during train collisions. The goal of this senior project was to create such a table using a composite sandwich structure designed to safely absorb energy. Testing of previous table designs was used to establish engineering specifications for the static loading, work surface durability, and impact performance requirements of the new table. Analytical and finite element models were used to analyze new concepts until a design was achieved that could meet all specifications. The tabletop developed consists of a crushable aluminum honeycomb core with fiberglass laminates on top and bottom. This sandwich structure uses a combination of E‐glass cloth and S‐glass unidirectional tape in a unique layup that lowers impact forces inflicted on the passenger while maintaining overall table strength during normal loading conditions. Four tables were built during the senior project. These tables were fabricated using a combination of fiberglass layup, metal working, welding, and adhesive bonding. Using these tables, four validation tests were conducted to evaluate the performance of the new design: work surface indent testing, vertical and horizontal static loading, quasi-static crush testing, and dynamic impact testing. The results of these tests showed that the new table met all of the engineering specifications outlined at the beginning of the project. The work surface was stronger than expected, showing deformation at a load of 175lbs; well above the requirement of 65lbs or more. The table easily withstood the 225lb vertical and 337lb horizontal static loading requirements at all critical locations. Quasi-static testing showed that a 1500‐2000lb edge load is needed to initiate crushing of the table. Although the desired goal of 800‐1000lb was not achieved, the facesheets did begin buckling in the unbounded sections as designed at about 1000lbs; only 100lbs from the 900lb buckling load predicted by FEA. Unfortunately, the tables continue to support load after initial buckling up to the witnessed 1500‐2000lbs. In dynamic impact testing, the table produced some of the lowest peak acceleration levels of any design to date. The peak acceleration levels recorded were 14g and 20g for the two impacting masses; well below the specification of 30g for any time period over 3ms. The tabletop structure also crushed evenly and the facesheets remained bonded and contained under the aluminum edging. The overall metal structure of the table also held its form, suggesting that the passenger would remain safe during such an impact. The new table costs about $475 and weighs 37lbs.