Document Type

Thesis - Open Access

Award Date


Degree Name

Master of Science (MS)


Civil and Environmental Engineering

First Advisor

Suzette Burckhard


3D printing, Environmental effect, Heat treatment, Humidity, Impact strength, Poly lactic acid


Environmental conditions have a significant effect on the mechanical properties of various materials. Environmental parameters such as temperature and humidity have a major impact on mechanical properties of materials such as compressive strength, tensile strength, bending strength and impact strength. The purpose of this research is to study how temperature and humidity affect the impact strength of 3D printed PLA plastic. Impact strength is the ability of a material to absorb energy subjected to an impact load by a pendulum. In this research, 3D printing was employed to produce PLA specimens which were later used for different experimental testings. For 100% humidity, six pairs of PLA specimens were heated in a water bath to reach a desired temperature, within the range 25⁰ C (±5⁰C) to 95⁰ C. For each different test, the temperature in the water bath was incremented by 10⁰ C to reach a maximum of 95⁰C. Thus, eight different temperature experiments were performed. Two PLA specimens were impact tested in time increments of two hours. Temperature effects were studied by heating six PLA specimens in a nonvacuum oven, at eight different temperatures as mentioned above. The specimens were later impact tested following ASTM D256 standards test methods for Determining Izod Pendulum Impact Toughness of Plastic Materials. The test results show impact strength of the PLA increased with an increase in temperature treatment. The PLA samples had the highest impact strength at higher temperature treatment but only for short heat treatment times. At low temperature treatment, the impact strength of PLA samples increased with an increase in treatment time. The samples impact tested after aging at room temperature post heat treatment have considerably shown low impact strength. This concludes, the impact strength of PLA is not sustaining with aging of samples. So, heat treatment can change the strength of 3D printed PLA but it was verified upon testing that the initial strength tested right after the heat treatment was not sustained over time as the impact strength of the samples decreased although not to the initial strength prior to heat treatment.



Number of Pages



South Dakota State University


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