Interlaminar Shear Strength of Carbon-Fibre Reinforced Thermoplastics Polycarbonate and Polysulfone

Abstract

The interlaminar shear strength (ILSS) of carbon-fibre reinforced polymers (CFRP) at room temperature (RT) depends on:

• a) properties of the reinforcing fibre

• b) properties of the pure matrix system

• c) interaction between fibre surface and matrix, caused by active surface groups

  At cryogenic temperatures two effects are superposed:

  • a) increasing matrix strength

  • b) “shrink-on” of the matrix on the fibre because of the strong matrix contraction by cooling

Both effects can cause improved mechanical composite properties. Negative side-effect of this shrinkage is the built-up of enormous thermal residual stresses at the fibre-matrix interface and therfore a more brittle fracture behaviour. Matrix systems having some low temperature ductility and high cryogenic fracture strain are necessary to overcome these problems.

Thermoplastic materials like polycarbonate (PC), polysulfone (PSU) and polyethersulfone (PES) seem to be promising candidate matrix materials.

The ILSS values, measured by short beam test on PC and PSU reinforced with HM- and HT-fibres at RT, 77K and 4.2 K are presented and discussed. A comparison is given of the different fracture behaviour of carbon fibre reinforced epoxies, polycarbonate and polysulfone.