Carbon fibre failure theory

Honours thesis for Bachelor of Engineering (Aerospace), UNSW, 2013

Failure prediction of composite materials (e.g. carbon fibre reinforced polymers) is still not well understood, requiring long and expensive test programs. Onset theory is a new composite failure theory based on strain invariants at the micromechanical level. In this project I applied onset theory to test specimens, examining variations in predictions and test results with temperature. This required extensive lab tensile testing of coupons, microscopy, and analytical predictions.

Tensile testing machine equipped with environment chamber, used to apply tensile loads to test specimens at different temperatures

Strain gauge on a test coupon used to accurately measure the level of strain in the specimen during tensile loading

Microscopy on crossply coupon reveals microcracking, indicating onset of damage

Strain applied to a specimen over time

Stress-strain curve

Methodology for determining loads for onset of composite failure