“…Additionally two lateral copper plates (one on each side of the mold) are fastened on the mold to separate the cavity from the ambient air and ensure a confined cavity. In order to avoid holding issues of the samples [33], the setup was designed with the moving platen sliding horizontally. Thus, the samples are simply positioned vertically on each platen, facing each other and resting on their sides.…”
Section: Experimental Welding Benchmentioning
confidence: 99%
“…This phenomenon has been observed by different authors. Harkous et al [33] attributed it to very rapid failure of the welded area and explained that, for high resistance composite, the large amount of energy released causes a long propagation of the crack and, consequently, a complete breaking of the part. Sacchetti et al [37] also observed this unstable behaviour for unidirectional Carbon/PEEK laminates and explained that it was due to a non-uniformity of the matrix rich layer at the surface of their samples, resulting in a non-uniform interlaminar fracture toughness along the crack path.…”
Thermoplastic welding, tape placement, 3D printing, overmoulding or even thermostamping involve adhesion of thermoplastic polymer at high temperature. Build-up of the mechanical resistance between two substrates is usually assumed to be driven by the diffusion of macromolecules at the interface, called healing phenomenon. Moreover, in continuous processes, such as some used in manufacturing of composites for aerospace structures, cycles are very short. Thus, there is a need for quantifying the adhesion of such materials especially when processed for short durations. With this aim, a temperature and pressure controlled welding bench was designed to enable the welding of double cantilever beam samples for short time (down to 1s). Adhesion of a carbon/PEKK composite was characterized over a wide range of residence times ranging from 1 second to 1 hour. Three bonding regimes were observed, corresponding to different stages of the adhesion build-up at the interface. Finally, the healing kinetics was identified.
“…Additionally two lateral copper plates (one on each side of the mold) are fastened on the mold to separate the cavity from the ambient air and ensure a confined cavity. In order to avoid holding issues of the samples [33], the setup was designed with the moving platen sliding horizontally. Thus, the samples are simply positioned vertically on each platen, facing each other and resting on their sides.…”
Section: Experimental Welding Benchmentioning
confidence: 99%
“…This phenomenon has been observed by different authors. Harkous et al [33] attributed it to very rapid failure of the welded area and explained that, for high resistance composite, the large amount of energy released causes a long propagation of the crack and, consequently, a complete breaking of the part. Sacchetti et al [37] also observed this unstable behaviour for unidirectional Carbon/PEEK laminates and explained that it was due to a non-uniformity of the matrix rich layer at the surface of their samples, resulting in a non-uniform interlaminar fracture toughness along the crack path.…”
Thermoplastic welding, tape placement, 3D printing, overmoulding or even thermostamping involve adhesion of thermoplastic polymer at high temperature. Build-up of the mechanical resistance between two substrates is usually assumed to be driven by the diffusion of macromolecules at the interface, called healing phenomenon. Moreover, in continuous processes, such as some used in manufacturing of composites for aerospace structures, cycles are very short. Thus, there is a need for quantifying the adhesion of such materials especially when processed for short durations. With this aim, a temperature and pressure controlled welding bench was designed to enable the welding of double cantilever beam samples for short time (down to 1s). Adhesion of a carbon/PEKK composite was characterized over a wide range of residence times ranging from 1 second to 1 hour. Three bonding regimes were observed, corresponding to different stages of the adhesion build-up at the interface. Finally, the healing kinetics was identified.
“…The riveting mechanism is shown in Figure 4.Figure 4.Riveting mechanism (a) drill hole in joining components; (b) positioning of joining components, and rivet insertion; (c) rivet tightening and joint consolidation through pressure; (d) a consolidated joint. 26 …”
Composite materials have found widespread applications in the automotive, aerospace, and building industries. Several components are joined together for these applications, by some temporary or permanent bonding approach. The increased use of different materials and their combinations such as composites makes the whole joining process something to be thoroughly considered before continuing. Several aspects need to be studied before spending significant time and financial resources. Considering these challenges in this paper we have provided a review of the investigations that have been made on fiber-reinforced composite joints. The level of development in various types of joints and joining techniques such as mechanical bonding, adhesive bonding, and fusion bonding along with their advantages and disadvantages is given. Several parameters affecting the performance of composite joints such as joint configuration, material selection and properties, geometric parameters, dominating failure modes, and environmental factors are described briefly. To verify the performance of composite joints, guidance on joint testing is given (both destructive and non-destructive).
“…Classically, the adhesion development between two thermoplastic parts requires the parts to be heated up to a temperature higher than the melting temperature of the polymeric matrix and pressed together [1,2]. The first step, where the assembly has no mechanical strength, is generally referred to the establishment of intimate contact at the interface which accounts for the initial roughness of both the adherents to explain that contact is not immediately perfect.…”
Thermoplastic composites offer new manufacturing prospects, thanks to the ability to melt the matrix. Welding, tape placement, 3D printing, overmoulding, or even stamping involve adhesion of the thermoplastic polymer at high temperature. First, under heat and pressure, contact at the microscopic scale is ensured by the deformation of surface roughness, this is the intimate contact step. Then, the development of the mechanical strength of the assembly is controlled by the diffusion of macromolecules at the interface which is defined as the healing step. Nowadays, continuous manufacturing processes tend to be faster and present very short residence time which could limit the adhesion development. A good understanding of these mechanisms is therefore very important to control and predict such industrial processes. Welding tests at different temperatures and contact pressures were carried out over a large range of residence times using a controlled welding bench enabling very short welding times (down to 1 second). The mechanical adhesion between PEKK-carbon composite samples was characterized using double cantilever beam fracture tests. Adhesion was found to develop in two steps which could be described as an intimate contact-healing coupled step and a pure healing step. From this, the healing kinetics was identified and an empirical model was developed to account for the effect of pressure on adhesion build-up. This model could then be compared with existing models to describe the establishment of intimate contact between the coupons.
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