Lamination Surface Defects in Composites
Poudel, Amrit (2020)
Poudel, Amrit
2020
Julkaisun pysyvä osoite on
https://urn.fi/URN:NBN:fi:amk-2020092820765
https://urn.fi/URN:NBN:fi:amk-2020092820765
Tiivistelmä
The manufacturing process of composites depends upon different factors. Fluctuation on those factors may leads to various defects on the product. Those defects can be seen on the surface of the composites. This thesis scope was to study the defects on the surface of laminate composites. The aim of this study was to study the surface defects through optical microscope and quantify the defects with analyzing their geometry and to find out how much the defects reduce the strength of specimens. Glass fiber with density of 2540kg/m3 and ATLAC E-Nova 6215 Vinyl ester resin with density 1140kg/m3 was used to manufacture laminate composites. Two fiber sheets represented as ‘A’ and ‘B’ were used with fabric orientation of 0/90/m70 and +45/-45/m100. Thirty different samples, grouped as ABA and BAB symmetric were used for the study. Samples were cut into length of 180mm per piece. Width of samples ABA symmetric ranged from 15.10mm to 15.20mm with thickness ranged from 5.25mm to 5. 60mm.Whereas, width of BAB symmetric samples ranged from 15.00mm to 15.15mm with thickness of 4mm to 4. 30mm.The surface of samples was analyzed on the microscope which helped to detect defects on samples. Air bubbles with diameter from 10micron to100 micron respectively were detected on samples. Using the dimension and analyzing the geometry of defect calculation was done to find the stress concentration factor around the defects which gave value of 3 for all defects.
Testometric machine was used for 3-point bending test from where the experimental data for flexural modulus was collected. Experimental flexural modulus for samples BAB symmetric ranged from 20425.73MPa to 22971.34MPa, whereas for sample ABA symmetric the value ranged from 22638.30MPa to 28921.57MPa. Composite Compressive Strength Modeller(CCSM) calculator was used to calculate the theoretical stiffness of the samples. The calculation gave flexural modulus for BAB symmetric samples ranged from 23714MPa to 26360MPa, whereas for ABA symmetric sample the value ranged from 289130MPa to 30605MPa. The data obtained from both of the calculation were compared. The sample with higher number of defects had the lowest experimental strength where the difference between experimental and theoretical strength was 5294.64MPa (BAB symmetric samples),7265.03MPa (ABA symmetric samples). The lowest difference of values was 2359.65MPa for BAB symmetric sample and 1683.43MPa for ABA symmetric samples. Both sample had lesser number of defects.
Testometric machine was used for 3-point bending test from where the experimental data for flexural modulus was collected. Experimental flexural modulus for samples BAB symmetric ranged from 20425.73MPa to 22971.34MPa, whereas for sample ABA symmetric the value ranged from 22638.30MPa to 28921.57MPa. Composite Compressive Strength Modeller(CCSM) calculator was used to calculate the theoretical stiffness of the samples. The calculation gave flexural modulus for BAB symmetric samples ranged from 23714MPa to 26360MPa, whereas for ABA symmetric sample the value ranged from 289130MPa to 30605MPa. The data obtained from both of the calculation were compared. The sample with higher number of defects had the lowest experimental strength where the difference between experimental and theoretical strength was 5294.64MPa (BAB symmetric samples),7265.03MPa (ABA symmetric samples). The lowest difference of values was 2359.65MPa for BAB symmetric sample and 1683.43MPa for ABA symmetric samples. Both sample had lesser number of defects.