The influence of surface roughness on the mechanical strength properties of machined short-fibre-reinforced thermoplastics

When a component is manufactured by machining, the surface roughness often differs from what is prescribed in standards on the preparation of test specimens for mechanical tests. If the surface roughness influences the strength, the properties of a machined part are therefore lower than the values given by the material supplier. The present study investigates the influence of the surface roughness of three machined short-fibre-reinforced thermoplastics (SFRTP) on the following strength properties: Charpy impact, monotonic bending and flexural fatigue. The strengths were found to be independent of the roughness when using a 5% level of significance. If this turns out to be true for other materials as well, the standards may need reassessment to avoid unnecessary work and unnecessary doubt about the use of the data. Furthermore, the production time can be lowered and there may be new advantageous applications of SFRTP.