TY - JOUR

T1 - Fatigue and fatigue after impact behaviour of Thin- and Thick-Ply composites observed by computed tomography

AU - Kötter, Benedikt

AU - Endres, Janina

AU - Körbelin, Johann

AU - Bittner, Florian

AU - Endres, Hans-Josef

AU - Fiedler, Bodo

PY - 2021/7

Y1 - 2021/7

N2 - This study investigates the influence of load ratio and impact damage on the fatigue behaviour of high-performance carbon fibre reinforced polymers (CFRP) with areal fibre weights between 30 gsm and 360 gsm. For undamaged samples, the ultimate tensile and compressive strength, as well as the fatigue properties, are evaluated with regard to their layer thicknesses. The fatigue tests were performed under tension-tension (R=0.1), tension-compression (R=-0.5) and compression-compression (R=10) regime. The results are illustrated as a constant-life diagram, and a piecewise linear interpolation examines a first prediction. The results show that static and fatigue performance improves with decreasing layer thickness. Particularly under tension-compression loading, significant improvements are observed, due to the suppression of matrix cracks and delaminations with thinner layers. In addition, the effect of low-energy impact on the fatigue behaviour of Thin- and Thick-Ply laminates is investigated. The tests demonstrate that although the delamination area is larger, Thin-Ply laminates can sustain higher stresses and still reach the same number of load cycles in contrast to Thick-Ply laminates. Computed tomography measurements visualize 3-dimensional the damage progression after various cycles and prove that the Thin-Ply composites show no increase in the damaged area during fatigue. The interlaminar stress at the delamination is not sufficient for expansion. In contrast, in the case of thicker layers, the damage growths progressively throughout the whole sample with increasing number of cycles.

AB - This study investigates the influence of load ratio and impact damage on the fatigue behaviour of high-performance carbon fibre reinforced polymers (CFRP) with areal fibre weights between 30 gsm and 360 gsm. For undamaged samples, the ultimate tensile and compressive strength, as well as the fatigue properties, are evaluated with regard to their layer thicknesses. The fatigue tests were performed under tension-tension (R=0.1), tension-compression (R=-0.5) and compression-compression (R=10) regime. The results are illustrated as a constant-life diagram, and a piecewise linear interpolation examines a first prediction. The results show that static and fatigue performance improves with decreasing layer thickness. Particularly under tension-compression loading, significant improvements are observed, due to the suppression of matrix cracks and delaminations with thinner layers. In addition, the effect of low-energy impact on the fatigue behaviour of Thin- and Thick-Ply laminates is investigated. The tests demonstrate that although the delamination area is larger, Thin-Ply laminates can sustain higher stresses and still reach the same number of load cycles in contrast to Thick-Ply laminates. Computed tomography measurements visualize 3-dimensional the damage progression after various cycles and prove that the Thin-Ply composites show no increase in the damaged area during fatigue. The interlaminar stress at the delamination is not sufficient for expansion. In contrast, in the case of thicker layers, the damage growths progressively throughout the whole sample with increasing number of cycles.

KW - Constant-life diagram

KW - Damage progression

KW - Delamination

KW - Load ratio

KW - Low-velocity impact

UR - http://www.scopus.com/inward/record.url?scp=85107862635&partnerID=8YFLogxK

U2 - 10.1016/j.jcomc.2021.100139

DO - 10.1016/j.jcomc.2021.100139

M3 - Article

VL - 5

JO - Composites Part C: Open Access

JF - Composites Part C: Open Access

M1 - 100139

ER -