Investigation of the thermoelastic response of long-fibre reinforced thermoplasticsby comparison with different non-contactstrain measurement techniques

Abstract

Processing of long-fibre reinforced thermoplastics with a discontinuous reinforcement of long glass fibres, especially by direct-processing, leads to inhomogeneous and anisotropic properties. Because of this, locally resolved characterisation of the material properties is necessary. Non-contact testing methods are required to derive these material properties. Locally resolving hysteresis measurement, full-field strain measurement techniques and thermoelastic stress analysis (TSA) are applied to an incremental step test and to a fatigue test. It is shown that there is good correspondence between the local TSA-signals and the locally measured values of the major strain. This correlation is valid not only for lower linear elastic load levels, but also up to nonlinear-viscoelastic levels. A model is presented to describe the correlation between the TSA-signal and the measured major strain.

Measurement of the thermoelastic response of short-fibre-reinforced polyamide 6 with application to a component under operating load

“…A stress-oriented investigation of the thermoelastic response of a laminated fibre-reinforced polymeric material with respect to the orthotropic stiffness of the whole laminate may lead to misinterpretations, if a significant transverse stress component is present in the surface layer. A significant transverse stress component appears in the surface layer of a uniaxially loaded specimen, if Poisson's ratios of the laminate and the surface lamina differ significantly [12]. For the material investigated in this research, it is assumed that the SRRL model is valid because of the presence of an isotropic SRRL layer (see section 3.1).…”