Strain Measurement on Composites: Effects due to Strain Gauge Misalignment

The present work analyses the errors affecting the strains measured by misaligned strain gauges installed on orthotropic-composite laminae. Various analytical relationships are derived showing that, besides the fibre and strain gauge orientations, the misalignment error in unidirectional off-axis orthotropic composite samples depends also on the lamina stiffness properties (E(1), E(2), nu(12), G(12)). If the fibres are aligned with the loading axis, it is found that the higher Poisson's ratio nu(12) is the only elastic property influencing the misalignment error. Experimental results are shown confirming the theoretical predictions