scholarly journals Discussion: “Damage Modeling in Random Short Glass Fiber Reinforced Composites Including Permanent Strain and Unilateral Effect” (Mir, H., Fafard, M., Bissonnette, B., and Dano, M. L., 2005, ASME J. Appl. Mech., 72, pp. 249–258)

2006 ◽  
Vol 73 (2) ◽  
pp. 347-348
Author(s):  
Noël Challamel ◽  
Christophe Lanos ◽  
Charles Casandjian
Keyword(s):  
Glass Fiber ◽  
Damage Mechanics ◽  
Continuum Damage Mechanics ◽  
Reinforced Composites ◽  
Glass Fiber Composites ◽  
Permanent Strain ◽  
Mechanics Model ◽  
Short Glass Fiber ◽  
Glass Fiber Reinforced ◽  
Short Glass

The paper of Mir et al. [ASME J. Appl. Mech., 72, pp. 249–258 (2005)] analyzes the deformation behavior of random short glass fiber composites using a continuum damage mechanics model incorporating permanent strain and unilateral effect. Unilateral effect is a difficult topic [see, for instance, J. L. Chaboche, Int. J. Damage Mech., 2, pp. 311–329 (1993)] and it seems to us that the model of Mir et al. still raises some questions.

Damage Modeling in Random Short Glass Fiber Reinforced Composites Including Permanent Strain and Unilateral Effect

2005 ◽  
Vol 72 (2) ◽  
pp. 249-258 ◽  
Author(s):  
Hicham Mir ◽  
Mario Fafard ◽  
Benoı^t Bissonnette ◽  
Marie-Laure Dano
Keyword(s):  
Glass Fiber ◽  
Thermodynamic Potential ◽  
Fiber Reinforced Composites ◽  
Internal Variables ◽  
Anisotropic Damage ◽  
Reinforced Composites ◽  
Permanent Strain ◽  
Short Glass Fiber ◽  
Glass Fiber Reinforced ◽  
Short Glass

This paper presents the development of a theoretical damage mechanics model applicable to random short glass fiber reinforced composites. This model is based on a macroscopic approach using internal variables together with a thermodynamic potential expressed in the stress space. Induced anisotropic damage, nonsymmetric tensile/compressive behavior (unilateral effect) and residual effects (permanent strain) are taken into account. The anisotropic damage is represented with second-order tensorial internal variables D. The unilateral effect due to microcrack closure in compression is introduced by generalizing the hypothesis of the complementary elastic energy equivalence. In the case of the permanent strain, a new term related to frozen energy, which is a function of the damage variable, the stress tensor, and some materials constants to be identified, is added to the basic thermodynamic potential. Using laboratory test results, parameter identification has been performed to illustrate the applicability of the proposed model.

scholarly journals Constant Temperature Approach for the Assessment of Injection Molding Parameter Influence on the Fatigue Behavior of Short Glass Fiber Reinforced Polyamide 6

Polymers ◽  
2021 ◽  
Vol 13 (10) ◽  
pp. 1569
Author(s):  
Selim Mrzljak ◽  
Alexander Delp ◽  
André Schlink ◽  
Jan-Christoph Zarges ◽  
Daniel Hülsbusch ◽  
...  
Keyword(s):  
Injection Molding ◽  
Glass Fiber ◽  
Process Parameters ◽  
Fatigue Properties ◽  
Injection Molding Process ◽  
Molding Process ◽  
Short Glass Fiber ◽  
Glass Fiber Reinforced ◽  
Molding Parameter ◽  
Short Glass

Short glass fiber reinforced plastics (SGFRP) offer superior mechanical properties compared to polymers, while still also enabling almost unlimited geometric variations of components at large-scale production. PA6-GF30 represents one of the most used SGFRP for series components, but the impact of injection molding process parameters on the fatigue properties is still insufficiently investigated. In this study, various injection molding parameter configurations were investigated on PA6-GF30. To take the significant frequency dependency into account, tension–tension fatigue tests were performed using multiple amplitude tests, considering surface temperature-adjusted frequency to limit self-heating. The frequency adjustment leads to shorter testing durations as well as up to 20% higher lifetime under fatigue loading. A higher melt temperature and volume flow rate during injection molding lead to an increase of 16% regarding fatigue life. In situ Xray microtomography analysis revealed that this result was attributed to a stronger fiber alignment with larger fiber lengths in the flow direction. Using digital volume correlation, differences of up to 100% in local strain values at the same stress level for different injection molding process parameters were identified. The results prove that the injection molding parameters have a high influence on the fatigue properties and thus offer a large optimization potential, e.g., with regard to the component design.

scholarly journals A Fatigue Damage Model for Life Prediction of Injection-Molded Short Glass Fiber-Reinforced Thermoplastic Composites

Polymers ◽  
2021 ◽  
Vol 13 (14) ◽  
pp. 2250
Author(s):  
Mohammad Amjadi ◽  
Ali Fatemi
Keyword(s):  
Injection Molding ◽  
Glass Fiber ◽  
Fatigue Damage ◽  
Life Prediction ◽  
Glass Fibers ◽  
Damage Model ◽  
Fiber Reinforced ◽  
Short Glass Fiber ◽  
Glass Fiber Reinforced ◽  
Short Glass

Short glass fiber-reinforced (SGFR) thermoplastics are used in many industries manufactured by injection molding which is the most common technique for polymeric parts production. Glass fibers are commonly used as the reinforced material with thermoplastics and injection molding. In this paper, a critical plane-based fatigue damage model is proposed for tension–tension or tension–compression fatigue life prediction of SGFR thermoplastics considering fiber orientation and mean stress effects. Temperature and frequency effects were also included by applying the proposed damage model into a general fatigue model. Model predictions are presented and discussed by comparing with the experimental data from the literature.

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