Effect of Defects on Mechanical Properties of Composites: Undergraduate Research on Materials

Undergraduate research in engineering and technology is gaining popularity as an added opportunity of learning and a gateway to advanced studies. Many students find undergraduate research as a tryout for potential graduate studies, as well as a way to establish relationship with research faculty. Albeit new in our Mechanical Engineering Technology department, two students were selected to participate in a research involving defects in composite materials. These students did have minimal background in composites from the general Engineering Materials course. These minority students were supported by summer scholarships from Peach State Louis Stokes Alliance for Minority Participation (PSLSAMP). The issue of defects and their effect on the mechanical properties of composites is of great concern among high end users. A limited set of experimental investigation with defective composite flat panels was selected for investigation. One of our adjunct faculty offered access to his fabrication facility and guidance to the students for fabricating these ‘defective’ panels. Three types of defects were incorporated: hole as a discontinuity, edge groove simulating transverse crack, and Teflon interlayer simulating delamination. Once the panels were fabricated, strips were cut out for testing. Students also learned special processes for cutting and drilling composites. Aluminum tabs ware glued to the ends of the composite strips to facilitate gripping by tensile tester. Two main testing methods were employed: tensile and 3-point bending. Unique failure modes of these specimens provided a lot of excitement as well as exposure regarding the mechanical behavior of composite materials containing defects. Certain correlations were observed between defects and resulting properties. Testing and results are far from complete. This endeavor provided great enthusiasm for engineering materials among the students. Other students have shown interest for continuing research on these and other materials projects.