Effect of steering limit constraints on the performance of variable stiffness laminates

Abstract

A method to optimise the fibre angle distribution of variable stiffness laminates is proposed. The proposed method integrates a fibre angle retrieval step with a fibre angle optimisation procedure. A multi-level approximation approach is used in combination with the method of successive approximations. First, fibre angle retrieval is done by approximating the structural responses based on the optimal stiffness distribution found using lamination parameters. The full fibre angle optimisation is done by updating the approximations based on the current stacking sequence. It is shown for a bucking optimisation with a stiffness constraint that the number of finite element analyses reduces significantly by starting the optimisation from the optimal stiffness distribution rather than from a user-specified stacking sequence. Next, it is shown that updating the approximations also leads to considerable improvements over fibre angle retrieval. Similar promising results are obtained for a stress optimisation problem.

Defect Characteristics and Online Detection Techniques During Manufacturing of FRPs Using Automated Fiber Placement: A Review

“…The works on conventional laminates in this review are summarized in Table 2. An important advantage of the AFP process is the possibility of making variable-stiffness laminates with curvilinear fiber paths to strengthen the structural buckling performance of composites [45][46][47][48][49][50][51]. However, to manufacture variable-stiffness components, since the tow has a certain width while translation distance remains constant, some imperfections are easier to form between the adjacent tows, mainly gaps and/or overlaps.…”

A design algorithm to model fibre paths for manufacturing of structurally optimised composite laminates

“…A two-step approach is proposed that takes as input a discrete fibre angle distribution resulting from structural optimisation, which is initially imported in the CAD environment where the algorithms for Design for Manufacturing are implemented. The method for structural optimisation of variable stiffness laminates was developed by Peeters et al [68,74,90,91] and comprises an optimisation of the stiffness distribution using lamination parameters [12] and a posterior fibre angle retrieval and optimisation [68,74,90,91]. Structural approximations of the Finite Element (FE) response are used to reduce the required number of FE analyses [92].…”

“…The variable stiffness design of a plate with a circular cut-out loaded in tension and optimised for strength has been undertaken. The details of the structural optimisation are found in Peeters et al [68]. The laminate is composed of 6 independent plies.…”

“…This method reduces the number of design variables an ease the consideration of manufacturing constraints while modelling continuous paths. However, the design space is limited due to the pre-specified set of possibilities [68]. A streamline analogy, also known as a fluid flow analogy, has been employed to compute continuous fibre paths from discrete fibre angles [4,21,23,31,59,69,70].…”

“…Other manufacturing features are considered in design, such as minimum curvature radius [12,32,[66][67][68][71][72][73][74][75] and minimum cut length [13]. For laminate analysis, studies have been conducted on capturing the influence of as-manufactured geometry and features such as gaps, overlaps, tow-drops and variable thickness for the analysis of VSL, by means of 3D FE models [48,[76][77][78][79][80][81][82][83], analytical methods [84] and experimental tests [13,81,[85][86][87].…”