Tensile damage in ternary melamine-formaldehyde composites

A new ternary planar random fiber composite (PRFC) is studied. It is a discontinuous glass fiber-reinforced, alumina trihydrate (ATH)-filled, melamine-formaldehyde (MF)-based composite of high fire resistance. Composites were manufactured from a commercially available molding compound using a Chopped Strand Mat (CSM), and compared with other ones obtained by varying the composition. Also, a comparison is made for grades with a high content of ATH but with different fiber architectures, realized by replacing the CSM mat by a needled mat. The amount and type of tensile damage is shown. An elastic-damage type parameter is discussed and used. In-situ Scanning Electron Microscopic (SEM) observations on polished surfaces of samples mounted in a tensile stage and subject to tensile load, and observations on as-obtained surfaces are made. Stress-strain behavior depending on damage is analyzed, and possibilities of improvement of mechanical properties are postulated.