An investigation of in-situ AFP process parameters using CF/LM-PAEK

Abstract

In recent years the use of thermoplastics has become popular in aerospace applications, with a primary focus on fiber-reinforced composites. Displaying greatly improved mechanical properties, new components using these materials still need to be characterized and their suitability for aviation applications demonstrated. A common restriction to the implementation of fiber-reinforced thermoplastic parts is the almost default autoclave manufacturing, which is both time consuming and expensive. Aiming for a more economical final product, this study utilizes a one-step in-situ Automated Fiber Placement (AFP) process to produce samples for mechanical and thermal characterization. The recently developed and highly popular material CF/LM-PAEK was used within this study, with the four major AFP processing parameters varied to assess material sensitivity. Test samples were manufactured using Design of Experiment (DoE). Subsequently, single lap shear (SLS) and differential scanning calorimetry (DSC) tests were performed to assess consolidation quality. With rising tooling temperature, both SLS strength and crystallinity increase up to 31 MPa and 25%, respectively. A post-manufacturing tempering process improved crystallinity of the tested CF/LM-PAEK specimens up to 29% and SLS strength up to 38 MPa. Within the tested parameter range, CF/LM-PAEK appeared to be unaffected by increasing layup speed, which is a promising aspect with regard to faster industrial production.

Consolidation of continuous-carbon-fiber-reinforced PAEK composites: a review

“…Though this will be discussed in more details in the last part of this review, a current limit is linked to the high speed of the roller (Fig. 4) causing fast cooling rates and thus low degrees of crystallinity [15,18,58,59,61]. For example, the crystallinity reached for "in-situ" consolidated CF/PAEK through AFP is around 10% as reported in [61] and 18% for CF/PEEK in the study of Comer et al [55], far below the ones obtained for autoclave processed pieces (see Table 1).…”

“…A second consequence of this short processing time is the fact that it will lead to low degrees of crystallinity, hence lower mechanical properties for the composite. To solve this, Schiel et al [61] propose to anneal afterwards the obtained laminate at a temperature above T g . Alternatively, increasing the tool temperature leads to lower cooling rates and higher degree of crystallinity as well.…”

Experimental investigation and optimization of thermal gradients by infrared welding

“…The deconsolidation phenomenon is well known in TPC processing, such as automated tape placement [3] or TPC thermal stamping. In these cases, mainly homogenous deconsolidation is investigated.…”

Design and manufacture of a reinforced fuselage structure through automatic laying-up and in-situ consolidation with co-consolidation of skin and stringers using thermoplastic composite materials

“…Crystallisation development, not only in terms of the degree of crystallisation but also in terms of the morphology, is a key consideration in in-situ consolidation. A recent study using novel materials (low melting poly-aryl-ether-ketone (PAEK)) demonstrated that several variations can be obtained in terms of the crystallinity and single lap shear by modifying the lamination speed, nip point temperature, and tooling temperature, and by performing post-manufacturing tempering [ 12 ].…”