Progressive Ply Failure Research Articles

Ultimate strength prediction of two-dimensional tri-axial braided composites based on an analytical laminate model

An analytical laminate model was newly proposed to predict the ultimate strengths of two-dimensional tri-axial braided composites under in-plane loadings. The composite was modeled as a laminate possessing four plies. Among these four plies, there were three plies consisting of unidirectional fibers along with surrounding matrix and one ply containing only matrix. A progressive ply failure analysis was performed. A series of experiments were conducted. The present model was verified experimentally by using our and other researchers’ data. Moreover, we compared this model’s results with the numerical ones obtained by us. The results show that the present model has the potential to predict the effective elastic properties and ultimate strengths of two-dimensional tri-axial braided composites. Finally, the effect of the braid angle on the mechanical properties of a two-dimensional tri-axial braided composite was explored based on the mentioned model.

Prediction of Progressive Ply Failure of Laminated Composite Structures: A Review

A review of recent developments in the progressive failure analysis of laminated composite structural elements such as beams, plates, panels and shells is presented in this paper. Composite materials are increasingly used to harness their advantages such as high strength to light weight, easy fabrication of structural components to the desired complicated geometry particularly in aerospace structures. Since the failure of composite laminates are progressive in nature compared to their metallic counter parts, it signifies to have better analysis methods to predict the progressive failure of laminated composites. A vast number of researches have taken place in this field. A few of the most relevant research articles are reviewed and presented here briefly.

Mechanisms of penetration in polyethylene reinforced cross-ply laminates

The mechanisms of progressive penetration for two ultrahigh molecular weight polyethylene (UHMWPE) reinforced laminates have been investigated. One used an UHMWPE fiber reinforcement while the other utilized molecularly aligned tape. Both materials had similar out of plane compressive strengths, but the fiber system had a 40% higher in plane tensile strength than the tape. Laminated, 6 mm thick plates with a [0°/90°] ply architecture were impacted by a 12.7 mm diameter sphere under conditions that either allowed out of plane plate deflection or eliminated this deflection by rear support of the target. The depth of penetration and the ballistic limit in the rear-supported tests were identical for the two materials, and proceeded by progressive ply failure. However, tests in the edge clamped condition resulted in a substantially higher penetration resistance, especially for the higher tensile strength fiber-reinforced material. Edge clamped testing of a bilayer target, where the front third was composed of the tape material and the remainder comprised fiber reinforced laminate, had the same ballistic limit as a target composed of only the higher ply tensile strength fiber reinforced material. Penetration in both test support conditions was discovered to occur by tensile ply rupture under the projectile, consistent with a recently proposed mechanism for converting out of plane compression to in plane ply tension. Lateral displacement of plies was also observed near the sides of impact craters in both materials, indicating the existence of a second mechanism impeding penetration of the spherical shaped projectile.

A Progressive Failure Analysis Applied to Fiber-Reinforced Composite Plates Subject to Out-of-Plane Bending

The ability to predict the structural response of composites offers a significant advantage to design engineers and provides the possibility of identifying structurally efficient composite assemblies. Various analytical and numerical models are possible, but care has to be taken to ensure that the appropriate structural performance and failure criteria are used. In particular, modeling the progressive failure of composite laminas requires robust and validated failure algorithms that are not only computationally efficient, but are also able to predict the load–deformation characteristics and to ultimately establish the failure load appropriately. This study looks into different progressive failure macromechanical algorithms applied to e-glass-fiber-reinforced composite plates subject to out-of-plane bending. The influence of different boundary conditions of the plates, ranging from fully clamped to simply supported ones, on their ultimate failure load is also investigated. The results are validated by experimental data found in the literature and show that boundary conditions have a significant influence on the predicted ultimate failure load. The study also shows that, in this case, the predominant failure mechanism is the failure of matrix, and after the redistribution of stresses, no consecutive failure due to fiber or fiber-matrix failure occurs in the lamina, therefore a sudden-degradation progressive ply failure algorithm based on the failure mode is sufficient to model the structural performance of composite plates subject to out-of-plane bending.

Bearing Strength Analysis of Single Mechanically Fastened Joint in Stitched Laminates

Experimental investigation is carried out to understand the bearing strength of stitched and unstitched uniweave T300/QY9512 laminates with single-lap single-bolt joint configuration in this article. The objectives of the studies are to determine the effects of stitching node position, stacking sequence, and hygrothermal environment on the bearing strength and the load–displacement curves of stitched laminates. A three-dimensional finite element model is also developed to investigate the bearing properties of mechanically fastened joints in unstitched and stitched laminates. Hashin's three-dimensional failure criterion is used to predict the progressive ply failure. The stitching node position effect is of primary interest. A good agreement between experimental results and numerical predictions is observed. The results show that the bearing strength decreased when the stitching node position was close to the hole boundary.

Analysis of bolted joints in composite laminates: Strains and bearing stiffness predictions

Abstract A review of the investigations conducted on mechanically fastened joints is presented. A finite-element model is developed to predict the response of pin-loaded composite plates. The model takes into account contact at the pin–hole interface, progressive damage, large deformation theory, and a nonlinear shear stress–strain relationship. To predict progressive ply failure, four different analyses combining Hashin and the maximum stress failure criteria, and different associated degradation rules are conducted. The objectives of the study are to determine the influence of the failure criteria and the associated degradation rules on the predictions of the strains around the hole and the bearing stiffness. Predictions are compared with experimental results. It appears that agreement between the two depends on an appropriate selection of the failure criterion and the degradation rule. Better agreement between experimental results and numerical predictions is observed with the maximum stress criterion.

Assessment of a Steel-Free Fiber Reinforced Polymer-Composite Modular Bridge System

The paper describes the development and characterization of a modular bridge system incorporating fiber reinforced polymer (FRP) composite girders connected by stiffened FRP deck panels which serve as both formwork and flexural reinforcement for a steel free concrete deck cast on top. The response of individual components and a two girder deck assemblage are characterized through full scale tests and it is shown that capacity is substantially greater than the design demand levels. Analytical predictions, based on laminated beam theory using progressive ply failure criteria, moment-curvature analysis and finite element models, are seen to compare well with experimental results.

Optimization of structural designs for a safe failure pattern: layered material systems

The optimization of structural designs for a safe failure of laminated material systems was analyzed along with built-in damage indicators. This design methodology is based on the concept of a characteristic failure signature (CFS) and three-dimensional laminate analysis of layered composite materials. The analytical model used is able to predict the CFS of a non-linear stress/strain response, accumulation of damage and failure behavior. The analysis of CFSs was based on an incremental formulation of a three-dimensional laminated media analysis coupled with a progressive ply failure methodology. CFSs are shown to have unique safety features which depend on the ply stacking sequence and predominant loading conditions for a particular industrial application. Various examples of tailoring a safe CFS for anisotropic laminated structures are discussed.

Stress and failure analysis of mechanically fastened joints in composite laminates

The literature published on single mechanically fastened joints in fiber-reinforced plastics is reviewed. A finite-element model is developed to predict the response of pin-loaded composite plates. The model takes into account contact at the pin–hole interface, progressive damage, large deformation theory, and a non-linear shear stress–strain relationship. To predict the progressive ply failure, the analysis combines Hashin and the maximum stress failure criteria. The objectives of the study are to determine the influence of the failure criteria, the inclusion of a non-linear shear behavior on the strength prediction and the load–pin displacement curve. The proposed model is used to predict the bearing response of composite plates with different stacking sequences. Good agreement between experimental results and numerical predictions is observed.