Oxidation induced changes in viscoelastic properties of a thermostable epoxy matrix

The thermal ageing of a neat epoxy matrix has been studied at 200°C in air by three complementary analytical techniques: optical microscopy, mechanical spectrometry and nano-indentation. Thermal oxidation is restricted in a superficial layer of about 195 µm of maximal thickness. It consists in a predominant chain scission process involving, in particular, chemical groups whose β motions have the highest degree of cooperativity and thus, are responsible for the high temperature side of β dissipation band. As a result, chain scissions decrease catastrophically the glass transition temperature, but also increase significantly the storage modulus at glassy plateau between Tβ and Tα. This phenomenon is called “internal antiplasticization”. Starting from these observations, the Di Marzio and Gilbert’s theories have been used in order to establish relationships between the glass transition temperature and number of chain scissions, and between the storage modulus and β transition activity respectively. The challenge is now to establish a relationship between the transition activity and the concentration of the corresponding chemical group

Influence Of Parameters On Mechanical Properties Of Thermoplastic Polymers Obtained By Fused Filament Fabrication (FFF)

Fused filament Fabrication (FFF) is one of the typical Rapid Prototyping (RP) process that can fabricate prototypes from various model materials. To predict the mechanical behaviour of FFF parts, it is necessary to understand their material properties, and the effect that the FFF build parameters have on this later. In this study, two thermoplastic polymers (ABS and PLA), obtained by two open source 3D printers are studied. The key printing parameters that we looked into were: layer height, pattern geometry and % of infill density, by keeping constant the fabrication orientation, perimeter overlap, velocity of deposit and model temperature. In the main body of this study, we provided a detailed description of the influence of these parameters on rigidity (Young Modulus) and yield stress (0.2 % of strain). For this purpose, Taguchi’s statistical experimental design technique was applied and compared to full design’s one. The results obtained from Taguchi’s method show that layer height and pattern geometry has no effect on the Young Modulus, as well as pattern geometry on Re0.2 response in the studied range of infill density, whereas true infill density potentially affects the considered responses. In addition, the layer height may also affect slightly the yield stress response. Moreover, a good concordance of Young Modulus evolution versus infill density has been observed for both ABS and PLA materials, as well as two experimental design methods

Production technology for polymeric composite materials by additive manufacturing methods

Additive manufacturing methods make it possible to create complex geometry parts, that cannot be produced by conventional methods. For manufacture of the products, composite polymeric materials can be used, both disperse-filled and filled with short or continuous fibers. Recently, more and more attention has been paid to reinforcing plastics with natural fibers. The study of the manufacturing process of a polymeric composite material filled with continuous natural fibers by the fused filament fabrication is presented

Investigation of the Strength Characteristics of Samples Made of Nylon by FFF Technology

Additive manufacturing of polymer products over the past decade has become widespread in various areas of industry. Using the FFF method, one of the most technologically simple methods of additive manufacturing, it is possible to produce parts from a large number of different materials, including wear-resistant nylon. This article reflects the process of manufacturing samples from nylon using FFF technology with various internal topologies, as well as tensile tests. The analysis of the obtained results is performed and the relationship between the structure of the sample and the limit of its strength is established. The FFF method is promising for developing methods for producing composite materials. The results of this article can be useful in choosing the necessary manufacturing parameters

Effect of Temperature on Fretting Fatigue Characteristics of Bismaleimide Matrix

For industrial composite structures, fretting friction is a critical problem. Thermosetting resins are promising materials for these structures due to good mechanical and thermal properties. Two mechanisms of the propagation of fatigue cracks in bismaleimide resin, i.e., the effect of the temperature and the type of the stress ate studied

Effects of the Infill Density on the Mechanical Properties of Nylon Specimens Made by Filament Fused Fabrication

Additive manufacturing of polymer products over the past decade has become widespread in various areas of industry. Using the fused filament fabrication (FFF) method, one of the most technologically simple methods of additive manufacturing, it is possible to produce parts from a large number of different materials, including wear-resistant nylon. The novelty of the work is properties investigation of ±45° filling configuration with different filling degree for nylon, as well as calculating the effect of infill on the strength characteristics, excluding the shell. This article reflects the process of manufacturing samples from nylon using FFF technology with various internal topologies, as well as tensile tests. The analysis of the obtained results is performed and the relationship between the structure of the sample and the limit of its strength is established. To calculate real filling degree and the effect of internal filling on the strength characteristics of the specimen, it is proposed to use a method based on the geometric and mass parameters. The FFF method is promising for developing methods for producing a composite material. The results of this article can be useful in choosing the necessary manufacturing parameters

On the difference in material structure and fatigue properties of polyamide specimens produced by fused filament fabrication and selective laser sintering

The present paper describes the influence of both flexure quasi-static and fatigue loading on polyamide 12 (PA12) specimens fabricated by fused filament fabrication (FFF) and selective laser sintering (SLS) processes. Rectangular prisms (ISO 178:2010) of polymer were printed and tested under sinusoidal three-point bending fatigue loading at a frequency of 5 Hz. The differences in porosity, surface roughness, and degree of crystallinity are systematically measured and linked to the mechanical fatigue properties. Fatigue analysis in the visco-elastic domain of the polymer is fully described, from fatigue behavior to energy analysis. Here, we have shown that the fatigue properties of the FFF specimens are found to be higher than those of the SLS specimens, despite their lower degree of crystallinity (more than four times). The presence of pores and their growth during fatigue tests in the sintered PA12 specimen seem to be responsible. The fatigue loss factor analysis shows that at lower stress levels, PA12 material reveals its characteristic slight visco-elastic dissipation and heating as its lifetime was exhausted. Also, the obtained results of additively manufactured PA12 were compared with those of materials obtained by injection molding (IM) and extrusion techniques. The quasi-static flexural properties of PA12 obtained by FFF and SLS processes reveal better character istics compared to IM and extruded specimens. However, the fatigue properties of the SLS-processed polymer are 24% and 40% less than those of materials obtained by IM and extrusion

The effect of build orientation on both flexural quasi-static and fatigue behaviours of filament deposited PA6 polymer

The present paper aims to study the effect of manufacturing build orientation on both flexural quasi-static and fatigue behaviours of semi-crystalline polyamide 6 obtained by Fused Filament Fabrication (FFF), by considering the porosity and surface roughness. The glass transition temperature, melting temperature, and crystallinity degree were measured complementary to understand better the process. Fatigue analysis is here fully described in visco-elastic domain of material. The results highlight that the XZ build orientation is better than the XY one and suggest that porosity plays an important role. The obtained results are also compared with conventional techniques given by the literature review

Flexural quasi-static and fatigue behaviours of fused filament deposited PA6 and PA12 polymers

The present paper aims to compare study the effect of porosity and degree of crystallinity on both quasi-static and fatigue behaviours of PA6 and PA12 specimens obtained by the fused filament fabrication (FFF). The glass transition and melting temperatures were measured complementary to understand better the process. Fatigue analysis is here described in visco-elastic domain of material. The results highlight that the mechanical and fatigue properties of PA 12 are better than those of PA6, in spite of almost amorphous state of PA12. Besides, porosity did not reveal the expected influence on these properties. The obtained results are also compared with conventional techniques given by the literature review