PSI - Issue 56

2

Author name / Structural Integrity Procedia 00 (2023) 000 – 000

Cristina Vălean et al. / Procedia Structural Integrity 56 (2024) 97– 104

98

1. Introduction Due to the possibility of obtaining complex parts with a high dimensional precision, additive manufacturing (AM) technology has gained a lot of attention in recent years compared to traditional technologies [1-3]. Among the AM technologies, the Fused Deposition Modelling (FDM) process is by far the most developed and used process [4]. This aspect is due to the friendly handling, low costs, acceptable precision and high properties of the printed components [5, 6]. FDM works with many thermoplastic materials, however, the most used is polylactic acid (PLA) [7]. The integration of the agricultural by-products in PLA filaments was approached by Calì et al [8]. The natural fillers in the biocompatible matrix opens the possibility of filaments to be used in biomedical field. The hemp and hemp inflorescences mixture in PLA matrix provide to the new composite significant improvements in elastic properties and density. The changings in hardness, density, tensile strength and melting temperature were presented by Lohar et al [9] in accordance to the addition of bio fillers in the PLA matrix. The wall nut shell powder, egg shell powder, white marble powder and combination of those were used as fillers in PLA matrix, producing composites that impact the properties of PLA. One of the most impacted properties are the elongation at break and the hardness of the new composites. These properties are enhanced by the presence of the bio fillers. Mei-Po et al [10] conduct tensile, flexural and impact properties of PLA reinforced with bamboo charcoal for food storage applications. An important aspect was observed, regarding the mechanical properties: the properties increase until a threshold value of 7.5 wt.% charcoal particles is reached, leading to the necessity of limiting the percentage of filler in mixture. Graphite was used as filler in PLA polymer matrix by Zerankeshi et al [11]. Acting as a reinforcement phase, the composite exhibit significant better printability and mechanical properties. Also, the thermal properties of the PLA graphite mixture were enhanced in comparison with untainted PLA. Some authors develop mathematical models of failure probability of PLA with and without fillers starting from static tensile testing [12]. The presence of the alumina particles in the polymeric matrix lowers the tensile strength both in raw filament and on the printed samples. The integration of nickel powder in the PLA matrix was approached by some authors [13]. They use the scanning electron microscopy for analyzing the uniformity of the particle distribution in the structure of the composite and reveal that some composites are not suitable to became filaments for 3D printing. The best results in this case were recorded for a 5% of nickel particles in the PLA volume. A comprehensive review work on the effect of presence of different fillers on PLA matrix was conducted by Joseph Arockiam et al [14]. Here, the mechanical and thermal properties of polylactic acid filaments containing various types of fillers were examined. Among considered fillers were: carbon fiber, microcrystalline cellulose, core-shell rubber, accelyted tannin, hemp hurn, cellulose nanofibers, continuous flax fiber, hemp and harakeke, wood, diatomaceous earth, bamboo fibers, talc, cork and ABS. Al results are presented in comparison with the untainted PLA materials but no comparison between the fillers was done. Therefore, this paper presents a comparison between several types of fillers (glass/carbon fibers and bronze particles) and pure PLA. The investigations are carried out under tensile and flexural loads.

Nomenclature AM

Additive Manufacturing Fused Deposition Modelling polylactic acid + glass fibres polylactic acid + carbon fibres polylactic acid + bronze particles polylactic acid

FDM PLA

PLA+GF PLA+CF PLA+BP