Modeling approaches laminate

Curing of Polyimlde Resin. Thermoset processing involves a large number of simultaneous and interacting phenomena, notably transient and coupled heat and mass transfer. This makes an empirical approach to process optimization difficult. For instance, it is often difficult to ascertain the time at which pressure should be applied to consolidate the laminate. If the pressure is applied too early, the low resin viscosity will lead to excessive bleed and flash. But if the pressure is applied too late, the diluent vapor pressure will be too high or the resin molecular mobility too low to prevent void formation. This example will outline the utility of our finite element code in providing an analytical model for these cure processes. 

Varve or rhythmites chronology is another approach based on the examination of geological materials. In this model, the distribution of the laminated sediments formed in the bottom of the beds of dried-out lakes (as a consequence of the seasonal melting of glaciers and the subsequent deposition of coarse particles supplied by streams, followed by finer materials such as sand, silt, and clay) is analyzed and correlated with climate changes [64],... 

In the past, various resin flow models have been proposed [2,15-19], Two main approaches to predicting resin flow behavior in laminates have been suggested in the literature thus far. In the first case, Kardos et al. [2], Loos and Springer [15], Williams et al. [16], and Gutowski [17] assume that a pressure gradient develops in the laminate both in the vertical and horizontal directions. These approaches describe the resin flow in the laminate in terms of Darcy s Law for flow in porous media, which requires knowledge of the fiber network permeability and resin viscosity. Fiber network permeability is a function of fiber diameter, the porosity or void ratio of the porous medium, and the shape factor of the fibers. Viscosity of the resin is essentially a function of the extent of reaction and temperature. The second major approach is that of Lindt et al. [18] who use lubrication theory approximations to calculate the components of squeezing flow created by compaction of the plies. The first approach predicts consolidation of the plies from the top (bleeder surface) down, but the second assumes a plane of symmetry at the horizontal midplane of the laminate. Experimental evidence thus far [19] seems to support the Darcy s Law approach. 

In this review we will present an approach to modeling the stability, growth, and transport of voids during autoclave laminate processing. Before presenting the model formulation and some results, it will be helpful to briefly examine the process details and some of the evidence for voids. 

In the past, various resin flow models have been proposed (2, 15-19). Two main approaches to predicting resin flow behavior in laminates have been suggested in the literature thus far. In the first case, Kardos et al.2), Loos and Springer15), Williams et al.16) and Gutowski17) assume that a pressure gradient develops in the laminate both in the vertical and horizontal directions. These approaches describe the resin flow in the laminate in terms of Darcy s Law for flow in porous media, which requires knowledge of the fiber network permeability and resin viscosity. Fiber... 

SFF encompasses many different approaches to additive fabrication, including Stereolithography (SLA), Selective Laser Sintering (SLS), Electron Beam Melting (EBM), Laminated Object Manufacturing (LOM), Fused Deposition Modeling (FDM), and 3D Printing. 

The simulation of the one-ply composite shows that the post-critical assumptions and the simple modelling procedure work fairly well — Figme 2.9. Hence, this approach can be used further for simulation of the four-ply laminate. A slight stiffening response of the material at the end of the test is probably caused by straightening of the yams in the loading direction, which has not been accounted in the model. 

The basic approach [1—4] starts with a single orthotropic ply. In the coordinate system of the ply, with one axis parallel to the fibers and one perpendicular to the fibers, in the plane of the ply, the stiffness properties are assumed known. These stiffness values may be obtained from analytical modelling at lower scales using micromechanics or may be obtained experimentally with 1 and 2 ply coordinates as opposed to the laminate coordinates x and y (see Figure 6.2). 

The effects of clearance on the stress distribution in the laminate around the hole boundary are presented first for a model in which homogeneous anisotropic material properties for the laminates were used. This is the approach often used in previous smdies, and gives an overview of the effects of clearance without the complexity... 

A future trend in composite bolted joint design is the use of more advanced continuum damage mechanics approaches to model joint failure, so that non-linear shear behaviour and gradual stiffness degradation can be implemented. An important element of joint failure is delamination, and many efforts are being undertaken to implement delamination in finite element models. However, for bolted joints analysis this poses many problems due to the large number of delamination interfaces in thick laminates. 

A comprehensive analysis of the use of EMIS for damage detection in laminated composites was presented in Bois and Hochard [18]. Figure 16.37 shows the experimental setup and the analytical model. A transfer-matrix method approach was used to compute the high-frequency dynamics of the delaminated composite beam and then... 

Another approach that has been used by researchers in simulating the damage characteristic of composite laminate during impact is based on the so-ealled eontinuum damage meehanics (CDM) constitutive model. This approach has been successfully implemented within LS-DYNA 3D and LS-DYNA 2D by van Hoof et al. (2001) and Nandlall and Chrysler (1998) respeetively. As in the previous approach used by Silva et al. (2005), they assumed that the response of an individual lamina is linear and elastic up to the point of failure, and that in the post-failure regime a lamina is idealized in a brittle manner, with the dominant... 

Finally, it can be concluded that the reversible work of adhesion at the fibre-matrix interface is an important parameter in determining the micromechanical behaviour of model composites as well as the ultimate properties of unidirectional laminates. Such a general approach could allow us to further improve the performances of advanced composites by controlling both the processing conditions and the level of interfacial interactions. 

Keywords grid strain analysis, Plytron , trellis effect, kinematic approach, finite-element approach (I M), analytical approach, anisotropy, hyperelastic, interply slip, intraply slip, thermoforming, modelling sheet forming, composite laminates, continuous fiber-reinforced composites. 

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