TY - THES

T1 - Damage mechanics of composites under fatigue loads

AU - Rieser, René

N1 - embargoed until null

PY - 2016

Y1 - 2016

N2 - This study investigates the fatigue behaviour of glass fibre reinforced polymer (GFRP) laminates. Unidirectional layups (UD), biaxial layups from ±15° to ±75° in 15° steps and a 0° dominated multiaxial layup were manufactured. Specimens were produced with the vacuum pressing technology. Damage evolution was observed in detail during the cyclic tension-tension fatigue test. It was linked to the decreasing cycle-dependent linear-elastic properties. Damage initiation and growth until specimen failure were observed using a camera system and transmitted light. It was found, that some layups do not develop a characteristic damage state (CDS) because delaminations evolved before crack accumulation in the entire specimen. The applied stresses in the fatigue tests were calculated with the classical laminate theory (CLT) and Puck’s failure criterion for static loads. It was used to show the unsuitability of a static approach under cyclic loads. Non-destructive testing (NDT) methods were evaluated for their applicability to damage monitoring during fatigue tests.

AB - This study investigates the fatigue behaviour of glass fibre reinforced polymer (GFRP) laminates. Unidirectional layups (UD), biaxial layups from ±15° to ±75° in 15° steps and a 0° dominated multiaxial layup were manufactured. Specimens were produced with the vacuum pressing technology. Damage evolution was observed in detail during the cyclic tension-tension fatigue test. It was linked to the decreasing cycle-dependent linear-elastic properties. Damage initiation and growth until specimen failure were observed using a camera system and transmitted light. It was found, that some layups do not develop a characteristic damage state (CDS) because delaminations evolved before crack accumulation in the entire specimen. The applied stresses in the fatigue tests were calculated with the classical laminate theory (CLT) and Puck’s failure criterion for static loads. It was used to show the unsuitability of a static approach under cyclic loads. Non-destructive testing (NDT) methods were evaluated for their applicability to damage monitoring during fatigue tests.

KW - Schädigungsmechanik

KW - faserverstärkte Kunststoffe

KW - Zerstörungsfreie Prüfung

KW - damage mechanics

KW - fatigue

KW - NDT

KW - non-destructive testing

KW - damage evolution

M3 - Master's Thesis

ER -