Assessment of process-induced deformations and stresses in ultra thick laminates using isoparametric 3D elements

Abstract

Shape distortions are a common problem experienced during the manufacturing of fiber reinforced plastics and are commonly investigated for thinner components. The following study presents the analysis of shape distortions and residual stresses in Ultra-thick laminates using a coupled thermomechanical approach. Existing studies frequently use high resolution meshes with multiple elements over ply thickness. This approach is not feasibly for thicker structures due to the computational effort. A new curing cycle, adapted to the requirements of Ultra-thick laminates, is deployed. Residual stresses need to be quantified and accounted for in the structural analysis. Several test components are manufactured in non-crimped fabric, to generate comparable data on heat distribution within the laminate and to measure the spring-in angle. For the FE analysis 3D stacked composite brick elements are used. These combine several plies within each element and present an efficient way to analyse thicker composite structures. Substantial residual stresses are calculated in the curved section of the laminate. A discrepancy in the calculated and measured spring-in angle is most likely explained by the usage of a single-sided steel tooling and several debulking steps.

A new specimen geometry to determine the through-thickness tensile strength of composite laminates

“…For thick laminates e.g. Zimmermann and Van Den Broucke [19] identified thermal residual stresses in the order of approximately 17% of the mechanical normal stress at failure load. Further assessment of the determined through-thickness strength can be done by tests in combination with FE analyses on sub-component level.…”

Novel epoxy powder for manufacturing thick-section composite parts under vacuum-bag-only conditions. Part I: Through-thickness process modelling

“…For forced convection BCs, Zimmermann and Van Den Broucke [49] recommended that a convective HTC of 10 -100 W/m 2 K be used for gases in an autoclave. Similarly, average convective HTCs have been experimentally measured in the range of 10 -40 W/m 2 K for autoclaves [50,51].…”

“…Assuming mass conservation for resin flow through the porous media, Where is the pressure at the flow front (assumed to be zero under vacuum conditions). As such, the equation reduces to: Rule of mixtures equations for the heat transfer model A rule of mixtures approach was implemented by several authors for describing the composite density and specific heat capacity within the heat equation[22,23,49,59,65,66]:Where is the volume fraction, and subscripts and denote fibre and resin, respectively.Equations for heat transfer through the bagging or toolingHeat transfer at the boundary of the laminate and bagging was written as, Where subscript represents the node at the boundary and is equivalent to node in the laminate. Note that the above can be easily written for the boundary of the laminate and tooling by changing the subscripts appropriately.The average spatial difference, ∆ , was approximated by, increment size for the bagging/tooling, represented by,…”

Multi-objective optimization of Resin Infusion

“…The pressure at the inlet was one bar, whereas the flow front was considered to be under vacuum. The thermochemical model and its constitutive laws used to simulate the cure of the materials involved in this study have been validated successfully against experimental results in previous work [24,25,30,34].…”