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Investigation of manufacturing continuous ﬁber reinforced thermoplastic polymer composites ( CFRTPCs ) through 3D printing technologies has attracted great attention in the past few years due to excellent properties of CFRTPCs , such as high strength-to-weight ratio and stiffness .
 manufacturing, reinforced, polymer composites, 3D printing technologies, properties, as, stiffness
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:
 manufacturing, reinforced, polymer composites, 3D printing technologies, properties, as, stiffness