Thermal response and edgewise compression failure of thermally degraded sandwich composite structures

Manufacturing and repair tasks using additive and subtractive laser processing (e.g., paint stripping and drilling) are becoming widely used in ships, aircrafts, and bridge structures. As with fire and exhaust impingement, such low level heat fluxes (<10 W) could negatively impact mechanical properties of composite structures. In this work, thermal excursions were simulated via continuous-wave laser exposure of the center region of a composite sandwich construction (i.e., E-glass fiber-reinforced vinyl ester matrix composite facesheets with a PVC foam core). Sandwich specimens were investigated with different slenderness ratios, facesheet thicknesses, foam core thicknesses and type of core materials. The 3-D temperature history response was measured with the spatially calibrated IR camera technology to map out the resulting damage state across the thickness of the specimens. The morphology of the foam core damage and interfacial debonding were postulated with the temperature profiles and evidenced by the X-ray CT images. Depending on the slenderness ratio and the volume of material heated above T-g, the thermally-induced damage significantly affects the edgewise compression strengths and failure modes.