Experimental investigation of the effect of defects in Automated Fibre Placement produced composite laminates

Abstract

Automated composite manufacturing processes such as Automated Tape Laying (ATL) and Automated Fibre Placement (AFP) are effective methods to produce high quality, lightweight parts. Typically, preimpregnated fibres or tapes are laid side-by-side onto a tooling surface to generate the composite preform. Although these two main technologies are widely used to produce large composite components, inconsistencies such as overlapping tapes or gaps between adjacent tapes may occur during the manufacturing. Within this study, the effect of gaps and overlaps, so-called defects, has been investigated experimentally. Tensile and compressive testing has been carried out on specimens with a quasi-isotropic, symmetric layup into which artificial defects in various defined formations were introduced. Of particular interest were the strength knockdown factors and changes in the failure mode.

Manufacturing-Induced Imperfections in Composite Parts Manufactured via Automated Fiber Placement

“…Investigations on quasi-isotropic laminates show that also the amount and arrangement of gaps and overlaps affect the laminate mechanical properties [51,76,78]. In addition, Li et al [51] and Lan et al [56,57] show the influence of the curing process on the geometric manifestation of gaps and overlaps.…”

“…Additionally, resin can accumulate within a gap during the autoclave process, which leads to a resin rich area [49,50,61,70]. Woigk et al [78] also identify fiber waviness as the origin of laminate failure in the transition zone of gaps and overlaps by means of microscope and high-speed images.…”

“…Corresponding testing guidelines or standards specify the specimen geometry, layup, test fixture and procedure on material and laminate level exactly. Some research groups [56,57,72,78,79] quantify the effects of gaps and overlaps on material and laminate level. Faló et al [73,74] experimentally investigate the damage tolerance of unconventional laminates.…”

Optimal orientation of fibre composites for strength based on Hashin’s criteria optimality conditions

“…Common composite production technologies, such as material hand layup and RTM (resin transfer moulding) (Dai and Hahn 2003;Magagnato et al 2018), have limitations in terms of delivering structures of variable stiffness design, since it is practically impossible to implement steered fibre paths with them. However, technologies such as AFP (automated fibre placement) (Lukaszewicz et al 2012;Woigk et al 2018), ATL (automated tape laying) (Sloan J 2008) and more recently FFF (fused filament fabrication), a type of additive manufacturing (often also referred to as 3D printing) (Nicoloso 2018;Matsuzaki et al 2016;Ferreira et al 2017;Dickson et al 2017;Yang et al 2017;Wang et al 2017;Zhuo et al 2017;Dutra et al 2019), have increased production flexibility in terms of curvilinear fibre reinforcements.…”

Effects of defects on laminate quality and mechanical performance in thermoplastic Automated Fiber Placement-based process chains

“…Many studies have considered the influence of defects on part performance in thermoset material [14][15][16][17][18][19][20][21][22]. There is a consensus among these publications that ply discontinuities can lead to local fiber misalignments, which then eventually have impact on the mechanical behavior of the laminate.…”