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The work here demonstrates the need for materials testing standards that are specific to additive manufacturing technologies ; as well as concluding that all-printed impact test specimens may offer the best representation of the impact characteristics of 3D printed structures .
 materials, standards, additive manufacturing, as, as, impact test, impact, 3D printed
Please list all entity words in the text that fit the category. Output format is "word1, word2". 
Option: manufacturing standard, machanical property, manufacturing process, material, engineering feature, process parameter, machine or equipment, application, process characterization, enabling technology, biomedical, concept or principle 
Text: {0} 
Answer:
 materials, standards, additive manufacturing, as, as, impact test, impact, 3D printed