Study on failure characteristic of phenolic fibers reinforced phenolic resin composites

Phenolic fibers reinforced phenolic resin composites were manufactured by a compression molding method. The flexural properties as well as interlaminar shear stress which tested by the short beam bending method and the failure modes of the composite materials at room temperature were study. And these properties of the composite specimens after high temperature treatment were also studied. And the mass loss rates of the composite specimens were researched by the oxyacetylene flame test and the failure characteristic of the composite at the high thermal environment were researched by the microstructure of the composites after oxyacetylene flame test. The results showed that, at room temperature, the average flexural strength and module of the composite specimen were low than those of the phenolic resin casting, and the composites were very brittle under loading which showed that the behaviors of the composite and the resin casting were alike. After high temperature treatment, the resin shrank and cracked, well the phenolic fibers connected the divided resin and the behaviors of the composite specimen were different with the phenolic resin casting. In the oxyacetylene flame test, the phenolic fibers and the phenolic resin matrix were pyrolysed at the same time, and the average mass loss rate of the composite specimens was 0.06 g/s. The microstructure of the composites after ablative test showed that during the resin matrix and the fibers charred they formed pillar-like arranged char at the same time. The char layer stick well at the vertical.