Effect of temperature and humidity conditions on polymethacrylimide (PMI) foam core material and indentation response of its sandwich structures

Abstract

Foam core sandwich structures are rather vulnerable against transverse loading which can leave only barely visible damage in the structures. Environmental conditions can further affect the loading response and thus the formation of damage. To study this, uniaxial compression-tension loading tests were conducted at 30, 60 and 80℃ temperatures using polymethacrylimide (PMI) foam specimens conditioned at three distinct humidity conditions (dry, ambient and wet) before testing. Effect of the conditions on the mechanical properties and loading response of the foam was studied. Strength and stiffness of the foam degraded with increasing temperature and humidity with the combined effect of these conditions being even more severe than either one alone. Indentation tests of polymethacrylimide foam core composite sandwich beams with composite face sheets were also conducted at the same temperature and humidity conditions. The indentation response was seen to correlate with the compressive response of the foam material.