Quantification Approaches for Fatigue Crack Resistance of Thermoplastic Tape Layered Composites with Multiple Delaminations

Abstract

Automated tape placement with in-situ consolidation (ATPisc) is a layer-wise manufacturing process in which the achievement of proper interlayer bonding constitutes one of the most challenging aspects. In the present study, unidirectional carbon fiber reinforced thermoplastic laminates were produced following different manufacturing protocols using ATPisc. The interlayer bonding of the laminates produced was characterized by mode I fatigue fracture tests with double cantilever beam (DCB) specimens. Independent of the manufacturing approach, the laminates exhibited multiple cracking during DCB testing, which could not be evaluated simply following standard methods. Thus, various data analysis methodologies from literature were applied for the quantitative assessment of the fracture behavior of the laminate. The examination of the evolution of the damage parameter φ and the effective flexural modulus throughout testing enabled a better understanding of the damage accumulation. The Hartman-Schijve based approach was revealed to be a convenient method to present fatigue crack growth curves of laminates with multiple delaminations. Moreover, a preliminary attempt was made to employ a ‘zero-fiber bridging’ methodology to eliminate the effect of additional damage processes on the fatigue crack growth that resulted in large-scale, partially massive fiber bridging.

In-Service Delaminations in FRP Structures under Operational Loading Conditions: Are Current Fracture Testing and Analysis on Coupons Sufficient for Capturing the Essential Effects for Reliable Predictions?

“…The occurrence of multiple delaminations has been experimentally observed [11,[15][16][17][18], even in unidirectional DCB specimens [17,57]. For Mode I DCB specimens.…”

“…(2) The differences between two-dimensional delamination propagation in plate-or shell-like structural elements versus essentially one-dimensional propagation in beam specimens (see, e.g., [12][13][14]). (3) How to approach the complications posed by multiple delaminations generated by impact or resulting from processing, e.g., by residual stresses, or often observed in multidirectional laminate lay-ups (see, e.g., [15][16][17][18][19]). ( 4) Approaches to reducing the 10-20% scatter typically observed in the repeatability and reproducibility of quasi-static and fatigue fracture test data, as well as reducing the differences between experiments and the modelling of structural behaviour, which can be up to 50%.…”

Accelerated aging tests vs field performance of PV modules

“…Fielded PV modules, in addition to the above-mentioned loads, experience alternating temperature cycles at different resolutions; hourly, daily, monthly, or annually. These temperature cycles induce thermo-mechanical stress/fatigue on a PV module, which mostly leads to degradation modes such as solder interconnections breakage, cell cracks, and glass breakage and fatigue of polymeric components [30,32]. Additionally, temperature cycles could also accelerate degradation mechanisms induced by other stresses.…”

On the Link between Plastic Wake Induced Crack Closure and the Fatigue Threshold

“…Indeed, variants of this approach have also been shown to be able to model delamination growth in composites as well as cohesive crack growth in adhesives and nanocomposites, see [31][32][33][34][35][36][37].…”