Topology and Size Optimization of Composite Ply Cargo Door

Structural optimization has seen accelerated deployment throughout all industries in the past decade, largely due to the recognition that tremendous efficiency gain can be achieved at concept design stage through topology optimization. For composite laminate design a three-phase optimization process is used. The target of the first phase is the material distribution in terms of orientation and thickness. This is achieved through topology optimization where thickness of each 'super-ply' of a unique fiber direction is allowed to change freely throughout the structure. As a result thickness contour of each fiber orientation is obtained. A discrete interpretation of the thickness contour results in concept design of ply layout and thickness. Then in Phase-II the interpreted ply-based structural model is further optimized under all design constraints with discrete design variables representing the number of plies of each ply patch. During Phase-III, ply stacking optimization is performed to refine the design according to detailed manufacturing constraints. All manufacturing constraints are considered throughout all three optimization phases. Such requirement would translate into percentage requirement during Phase-I and II so that a balanced distribution of fiber orientation is achieved to allow feasible stacking during Phase-III. The three-phase optimization process is illustrated in this paper. A unique modeling technique developed in conjunction with the optimization process is the ply-based finite element analysis model where ply entities are defined as sets of elements. Then ply layup is specified by a stack definition. In the following sections the procedure is demonstrated for one of the preliminary configurations developed for the composite cargo door

Impact of woven fabric: Experiments and mesostructure-based continuum-level simulations

Woven fabric is an increasingly important component of many defense and commercial systems, including deployable structures, restraint systems, numerous forms of protective armor, and a variety of structural applications where it serves as the reinforcement phase of composite materials. With the prevalence of these systems and the desire to explore new applications, acomprehensive, computationally efficient model for the deformation of woven fabrics is needed. However, modeling woven fabrics is difficult due, inparticular, to the need to simulate the response both at the scale of the entire fabric and at the meso-level, the scale of the yarns that compose the weave. Here, we present finite elements for the simulation of the three- dimensional, high-rated eformation of woven fabric. We employ a continuum- level modeling technique that, through the use of an appropriate unit cell, captures the evolution of the mesostructure of the fabric without explicitly modeling every yarn. Displacement degrees of freedom and degrees of freedom representing the change in crimp amplitude of each yarn family fully determine the deformed geometry of the mesostructure of the fabric, which in turn provides, through the constitutive relations, the internal nodal forces. In order to verify the accuracy of the elements, instrumented ballistic impact experiments with projectile velocities of 22–550 m/s were conducted on single layers of Kevlar ® fabric. Simulations of the experiments demonstrate that the finite elements are capable of efficiently simulating large, complex structures