This paper focuses on the analysis of drilling induced damage on biocomposites (woven fibers of cotton, flax and jute combined with polylactic acid, PLA, as the matrix). The main contribution of this work is the analysis of the influence of cutting parameters and drill geometry on fully biodegradable composites based on two different types of PLA and different fibers types. The damaged area was studied both at the hole entry and exit. Contrary to the behavior commonly observed when drilling conventional composites, delamination was negligible. The hole entry and exit damage were analyzed and quantified in terms of the fraying extension being the dominant. The damage extension was found to be dependent on the matrix, fiber type and drill geometry. The combination between cotton fiber and the small drill point angle showed the lowest level of damage. On the other hand, composite reinforced with flax fibers (those that exhibited the highest tensile strength) presented the greatest damage extension, increasing with the number of layers of the composite. The matrix based on polymer 10361D PLA, recommended for natural fibers because of the better interface cohesion, resulted in reduced fraying. Concerning the influence of cutting parameters, damage decreased when increasing the cutting speed and feed rate.
The study of the impact behaviour and the post-impact residual strength of fully biodegradable composites is presented in this work. To this end, low-velocity impact tests and compressive residual strength tests were carried out on flax/PLA laminates. The results were compared with carbon/epoxy laminates showing some important advantages in terms of absorbed energy and normalized residual strength. The reason was attributed to different energy absorption mechanisms; the main failure mode in flax/PLA laminates is fibre failure while residual strength of carbon/epoxy laminates is dominated by delaminations.
All-Cellulose Composites (ACC) are entirely manufactured from cellulose, resulting a fully biodegradable material with perfect compatibility between matrix and reinforcement. In this study, a finite element numerical model to predict the lowvelocity impact behaviour of ACC laminates is reported for the first time. The model was validated through comparison with experimental data from scientific literature conducted on ACC plates made from Cordenka woven plies. In addition, the model was applied to the analysis of failure modes and influence of impact energy.
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