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 failu re modes for both 10 and 25 mm thick glass/polyester woven fabric lami nates. For a given L/t the failure mode was affected by loading type a nd loading roller diameter. Laminated beam theory was modified to acco unt for unequal moduli in tension and compression, as measured in the uniaxial tests. Its predictions were in good agreement with experiment al results. Statistical strength theory was developed to explain the s tressed volume effect between three- and four-point flexural strength, and the stress gradient effect between compressive strength and flexu ral strengths. Statistical strength theory and a fracture mechanics me thod were used to investigate the strength scale effect. Reasonably go od agreement was obtained, provided that the primary mode of failure w as similar.