Characterization of thick glass woven roving/polyester laminates: 2. Flexure and statistical considerations

Experimental results of flexure tests in three- and four-point loading are presented, along with their stress-strain relationships and failure modes for both 10 and 25 mm thick glass/polyester woven fabric laminates. For a given L/t the failure mode was affected by loading type and loading roller diameter. Laminated beam theory was modified to account for unequal moduli in tension and compression, as measured in the uniaxial tests. Its predictions were in good agreement with experimental results. Statistical strength theory was developed to explain the stressed volume effect between three- and four-point flexural strength, and the stress gradient effect between compressive strength and flexural strengths. Statistical strength theory and a fracture mechanics method were used to investigate the strength scale effect. Reasonably good agreement was obtained, provided that the primary mode of failure was similar.