Department of Mechanical Engineering at Union College Senior Project Preliminary Proposal for the Academic Year

Transcription

1 Department of Mechanical Engineering at Union College Senior Project Preliminary Proposal for the Academic Year INVESTIGATION OF THE DAMAGE TOLERANCE OF COMPOSITE MATERIALS AT CRYOGENIC TEMPERATURES Proposing Student Jane Doe Associated Student John Doe 1 May 2008 Academic Terms Fall 08 and Winter 09 COMMITTED Faculty Member Ronald B. Bucinell, Ph.D., P.E.

2 INTRODUCTION Background NASA has the mission of providing revolutionary new tools and technology advancements for the Nation s aeronautics and space needs. The goals of this mission are wellarticulated in Daniel Goldin s Three Pillars for Success. In all three pillars (Global Civil Aviation, Revolutionary Technology Leaps, and Access to Space) advancements in materials is identified as being mission critical and composite materials are singled out as critical enabling technology. The goal of the Access to Space pillar is to reduce the cost of placing payloads in low earth orbit by ten-fold. One of the major programs under this pillar is the development of Reusable Launch Vehicles (RLVs). The RLV program is setting out to design launch vehicles that can achieve affordable access to space with systems that are highly reliable and have rapid turn-around. Part of the strategy is to reduce the weight of the launch vehicle in order to eliminate the need for multiple booster rockets. Achieving this will require that more efficient structures and materials be integrated into the launch vehicle. The tailorability and high specific properties of composite materials make them attractive for this application. NASA s is currently exploring the integration of composite into as many components of the RLVs as possible. Many of the RLV components are exposed to cryogenic temperatures and experience with composite materials at these temperatures is limited. Few composite materials have been characterized at cryogenic temperatures and the characterizations that have been performed have mostly been quasi-static in nature. The RLV environment is more complex than this. For the application of composite materials in this environment damage tolerance, impact, and fatigue characterizations all need to be considered. Cryogenic effects on composite materials have gained considerable attention in the super conducting industry. A through review of the affect of cryogenic temperature on composite materials is found in [1]. In this review the authors have summarized the results of many other researchers, they report standardized test results for many thermoplastic and thermoset resin systems that are reinforced with graphite fibers and tested at cryogenic temperatures. One of the findings from this review that is of particular interest is that as the temperature decreases the occurrence of microcracks also decreases. Reference [2] also investigates the affect of cryogenic temperatures on composite materials and makes the point that the availability of data on dynamic or fatigue characterization of composites at cryogenic temperatures is extremely limited yet essential to engineering design. An investigation of matrix dominated properties was reported on in [3]. This investigation also found that microcracks decreased with temperature. Since microcrack formation is an energy absorbing mechanism in composite materials that is related to toughness, the authors concluded that as temperature decreases so does the composites toughness. Toughness becomes a critical issue in both fatigue and impact load scenarios. The literature is filled with papers related to fatigue and impact loading of composite materials. This literature is lacking in investigations of fatigue and impact loading at cryogenic temperatures.

3 Purpose This project proposes to investigate the characteristics of composite materials that are subjected to cryogenic environments that are similar to those experienced by RLVs. The areas that this proposed study will focus on include thermal-mechanical characterization, damage tolerance, impact, and fatigue of composite materials at cryogenic temperatures. Scope The scope of this proposed program will be to further the understanding of how cryogenic temperatures impact composite materials. Both thermoplastic and thermoset resins reinforced with graphite fibers will be characterized. The characterization will include quasistatic, fatigue, and impact loading. Most important, this investigation will start to address scaling issues that directly impact design of composite structures. Approach DISCUSSION The objective of the proposed project is to evaluate the effects of subjecting composite materials to cryogenic temperatures. The approach that is being proposed is an experimental investigation that will include thermal-mechanical, damage tolerance, impact, and fatigue characterization. To achieve the objectives of this proposed project experimental equipment specifically designed to characterize materials at cryogenic temperature needs to be designed and built. After this the experiments will be performed to generated statistically significant characterizations of the behavior of polymer composites under cryogenic temperatures. A task by task description of the proposed program is described later in this section. Results The expected significance of this proposed program will be to further the understanding of how cryogenic temperatures impact composite materials. Both thermoplastic and thermoset resins reinforced with graphite fibers will be characterized. The characterization will include quasi-static, fatigue, and impact loading. Most important, this investigation will start to address scaling issues that directly impact design of composite structures. This investigation will also develop new techniques to characterize polymer composite materials at cryogenic temperatures.

4 Statement of Work Task 1: Damage Tolerance Investigation (DTI) What is Planned? As part of this task a thermal-mechanical characterization of composite materials at cryogenic temperatures will be carried out. This characterization will include determination of thermal expansion coefficients, static properties, fatigue characteristics, and impact characteristics. This evaluation will include both thermoplastic and thermoset matrices reinforced with graphite fibers. How Will Work be Carried Out? For this task, specimens will be manufactured in the Union College Composites Materials Manufacturing Laboratory. Samples will be prepare for characterization using standard test methods in the Union College Mechanics of Materials Laboratory. The Final Product to be Delivered? As a result of this effort, data on the characteristics of composite materials subjected to quasi-static, fatigue, and impact loading at cryogenic temperatures will be generated. Task 2: Gas Gun Impact Development (GGID) What is Planned? The emphasis in this task is on designing and constructing a gas gun impacter for the purpose of evaluating the response of composite materials to dynamic impact loading events. The impacter will be built to accommodate projectiles with various tip geometries and weights. A constraint system will also be designed to hold composite samples with of various size and boundary conditions. How Will Work be Carried Out? Union College, using Union College Machine Shop Facilities, will carry out the design and manufacturing of the dynamic impact gun. The design will be based on the previous gas gun experience of the PI. The Final Product to be Delivered? The result of this task will be a gas gun that will be capable of characterizing dynamic impact response of composite materials, including at cryogenic temperatures. Task 3: Development of Quasi-Static Pendulum Impacter (DQSPI) What is Planned? The emphasis in this task is on designing and constructing a pendulum impacter for the purpose of evaluating the response of composite materials to quasi-static impact loading events. The impacter will be built to accommodate projectiles with various tip geometries and weights. A constraint system will also be designed to hold composite samples of various size and boundary conditions.

5 How Will Work be Carried Out? Union College, using Union College Machine Shop Facilities, will carry out the design and manufacturing of the pendulum impact gun. The design will be based on the previous gas gun experience of the PI. The Final Product to be Delivered? The result of this task will be a pendulum impactor that will be capable of characterizing quasi-static impact response of composite materials, including at cryogenic temperatures. Time Line Week Task 1: DTI a. Research b. Design c. Implementation d. Experimentation e. Reduction Task 2: GGID a. Research b. Design c. Implementation d. Experimentation e. Reduction Task 3: DQSPI a. Research b. Design c. Implementation d. Experimentation e. Reduction Reports a. Progress b. Presentation c. Poster d. Draft of Final e. Final

6 RESOURCES Facilities and Equipment All the facilities that are required for the successful completion of this project are on the campus of Union College. The design of the experimental will be performed using SolidWorks design tools that are available on the computers in the Department of Mechanical Engineering. The fabrication of the test equipment will be performed using the machine shop in the Engineering Lab on campus. The fabrication of the test specimens will be conducted in the Composite Materials Fabrication Facility in Butterfield Hall and the experimental testing will be conducted in the Mechanics Laboratory in Butterfield Hall. All data analysis will be performed using the computer facilities in the Department of Mechanical Engineering at Union College Budget A. SALARIES Faculty Shop Labor Undergraduate Summer Stipend N/A N/A N/A B. EQUIPMENT $51,000 Thermo-Mechanical Analyzer $51,000 C. CONSUMABLES $ 7,500 Composite Prepreg $ 3,000 Steel for Impacters $ 1,500 Instrumentation $ 3,000 TOTAL $ 58,500 Funding for this project will come from several sources. $57,000 will be funded from a NASA Grant, $1,000 will be funded from a research account, and IEF will be asked to contribute $500. SUMMARY The successful completion of this project will result in the development of a database of materials characterization data for polymeric composite materials subjected to cryogenic temperatures. This data will have a significant impact on making the RLV efforts at NASA a reality. The risk associated with this proposal is that the time line is very short and any delays in procurement of materials or supplies could cause some of the testing to slip outside the twenty week window.

7 REFERENCES 1 Reed, R.P., Golda, M., Cryogenic Properties of Unidirectional Composites, Cryogenics, 34 (1994), p Hirokawa, T., Yasuda, J., Iwasaki, Y., Noma, K., Nishijima, S., Okada, T., Design of Support Strap with Advanced Composite for Cryogenic Applications, Cryogenics, 31(1991), p Nettles, A.T., Biss, E.J., Low Temperature Mechanical Testing of Carbon-Fiber/Epoxy- Resin Composite Materials, NASA Technical Paper 3663, (1996).