Inter-layer thermal contact resistance evolution with the degree of intimate contact in the processing of thermoplastic composite laminates

Abstract

This paper focuses on the contact between layers in forming processes of composite laminate. The link between the degree of intimate contact and the consequent thermal contact resistance between layers is investigated. A hot plate forming process experiment allows to propose a relation and determine the missing parameter for APC2 thermoplastic prepreg composite. Beside the new proposed relation, this work showed that the internal thermal contact resistances in the laminate is significant. Therefore, thermal modeling of forming processes of composite laminate (such as automatic tape placement) should account for this phenomenon.

Effects of material and process parameters on in-situ consolidation

“…Many studies in the past considered the deformation of rough surfaces squeezed under the action of an external applied pressure, using different representations of rough surfaces [8,12]. The characterization of random surfaces and the effect of roughness on physics defined at the surface level is a recurrent issue widely addressed in many works [13,14].…”

“…A critical aspect concerns the consolidation step, when the bonding occurs. This aspect widely treated in several works [12,[20][21][22] considers surface descriptors based on the use of rectangular elements (emulating the asperities) or fractals. However, analyses seem to reveal that those descriptions are not discriminant enough, that is, the same descriptors could represent surface exhibiting very different evolutions of the degree of intimate contact -DIC -.…”

An inverse model for optimisation of laser heat flux distributions in an automated laser tape placement process for carbon-fibre/PEEK

“…The consolidation roller then presses the molten surfaces together as they cool, resulting in a bond. The bonding process is a combination of the flattening of the asperities at the interface (intimate contact development [11][12][13]), and the diffusion of polymer chains across the interface (autohesion or healing [14][15][16]). Other physical processes occur simultaneously during the process such as changes in crystallinity [5,17,18], void content [9,19], residual stress [20,21] and degradation [22,23] -all of which are sensitive to the specific temperature history.…”

The effects of heat input on adjacent paths during Automated Fibre Placement

“…For toughened AFP materials, surface roughness plays a major role concerning void content and tack [17], as well as for through-thickness thermal conductance [18]. Levy et al [19] state the significance of the effect of thermal contact resistance for thermoplastic automated placement processes.…”