DERAKANE Fabricating Tips - 34 / 56 Pages
Inspecting a laminate
CHECKING FOR COMPLETE CURE
Barcol hardness values are used to indicate the completeness of resin cure in FRP laminates. To test for Barcol hardness, use the Barcol Tester #934.1* to take readings on both the inside and outside surfaces of the part (10 to 12 readings in all). Reject the highest and lowest readings, and average the remaining values to get the Barcol hardness value.
• Calibrate the Barcol Tester with both high and low hardness discs, and check it frequently.
• Use the Barcol Tester at room temperature (about 77°F [25°C]).
• When using the tester, keep it level. Be sure the point is perpendicular to the laminate surface.
• Clean or replace Barcol points frequently.
• Be sure to take measurements at secondary bonds, such as flanges and internal connections. Values at these points are critical.
• Laminates with high glass filling may give abnormally high Barcol values when the point hits glass.
• Contacting a synthetic veil may cause a drop of 2 to 3 points.
• Improper catalyst ratios may cause low Barcol readings.
• Incomplete catalyst mixing may cause widely varying readings.
• Heavy residual wax on the surface will cause low Barcol readings. Lightly sand off 1 to 2 mils of wax and test again.
RECOGNIZING FRP DEFECTS
Most FRP inspection, other than hardness checking, is visual, because physical testing is generally destructive. However, defects can be identified by observing the finished construction. The list of defects found on pages 33-35 can be used to help identify problems and correct fabricating techniques.
Table 9.1 - Typical Barcol Tested Hardness
* Product of Barber-Coleman Company ** RT = Room Temperature
This bulletin contains tips and suggestions, but no warranty, expressed or implied, is given; fabricators are advised to determine suitability as to any product, additive, process, formula, ratio, or end-use through their own expertise or tests.