Creep Response of Assemblies Bonded With Pressure Sensitive Adhesive (PSA)

2018 ◽  
Author(s):  
Hao Huang ◽  
Qian Jiang ◽  
Abhijit Dasgupta ◽  
Ehsan Mirbagheri ◽  
Krishna Darbha
Keyword(s):  
Hydrostatic Stress ◽  
Experimental Results ◽  
Double Layers ◽  
Material System ◽  
Secondary Creep ◽  
Loading Conditions ◽  
Stress Strain ◽  
Creep Response ◽  
Strain Behavior ◽  
Pressure Sensitive

Creep response of joints bonded with single-layered pressure sensitive adhesives (PSAs) was investigated in this study. PSAs are becoming more and more popular in the electronic industry as bonding media because of their ease of design, fast accurate bonding, environmentally-friendly bonding and ease of reworking. Such adhesive bonds are expected to experience complex, sustained loading conditions in service; e.g. loading due to large mass components, shock, temperature, or alignment mismatch of substrates. Stress-strain behavior of PSA bonding assembly has been extensively studied through experiments and simulations, including the effects of loading conditions (loading rate and temperature), PSA configurations (thickness of adhesive and single/double-layered PSAs), and bonding substrate surface properties (substrate material and surface roughness). However, the literature regarding the creep response of PSA-bonded assemblies is lacking and there is no literature on modeling methodologies for the creep response of such bonding systems. Similar to the stress-strain behavior of PSA-bonded assemblies, the creep response includes transitions between multiple hardening and softening phases. Experimental results indicate that the secondary creep rate can change by up to two orders of magnitude after each transition, which is too significant to ignore when estimating the creep deformation of joints bonded with this material system. The number of transitions is related to the configuration of the PSA system, i.e. the single-layered PSA has one transition while double-layers PSAs may have multiple transitions due to the additional interface(s) introduced by the carrier layer. This unique secondary creep behavior comes from the competition between hydrostatic stress relaxation and strain hardening, caused by cavitation and fibrillation processes, respectively. The total stress applied on the joint is equal to the summation of deviatoric stress and hydrostatic stress. An advanced model based on the stress-strain ‘block’ model [5–7] is developed for evaluating the creep response. This model has the capability to control the initiation and growth of cavities in the bulk of the PSA and at the interface between PSA and substrate. This model is able to capture the nonlinear visco-plastic behavior of the PSA fibrils and estimate the effects of flexible carrier layer on the transitions in creep curves. The model prediction shows reasonable agreement with experimental results in terms of the characteristic features in creep strain histories.

Mechanical Characterization of Assemblies Bonded With Pressure-Sensitive Adhesives (PSAs)

2015 ◽  
Author(s):  
Hao Huang ◽  
Abhijit Dasgupta ◽  
Ehsan Mirbagheri ◽  
Srini Boddapati
Keyword(s):  
Mechanical Behavior ◽  
Failure Modes ◽  
Mechanical Characterization ◽  
Bonding Temperature ◽  
Process Conditions ◽  
Second Phase ◽  
Loading Conditions ◽  
Stress Strain ◽  
Strain Behavior ◽  
Pressure Sensitive

The focus of this paper is on the stress-strain behavior and creep response of a pressure-sensitive adhesive (PSA) with and without carrier layers. This study consists of two phases. The first phase focuses on understanding of the effects of fabrication profiles, including bonding pressure, bonding temperature, bonding time, and aging time, on the PSA joint strength. This part of the study is used to identify an acceptable bonding and aging conditions for manufacturing a robust PSA bonded assembly. Specimens fabricated with this selected set of bonding process conditions are then used for mechanical characterization. The second phase focuses on the assembly’s mechanical behavior (stress-strain behavior and the creep curves) under different loading conditions, including loading stress, loading rate, and loading temperature. The mechanical behavior of PSA bonded assemblies is affected not only by the loading conditions, but also by the assembly architecture. The mechanical behaviors and failure modes of PSAs with and without carrier layers are compared. The reasons for these differences are also discussed.

Studies on the Stress-Strain Relationship Bovine Cortical Bone Based on Ramberg–Osgood Equation

2019 ◽  
Vol 141 (4) ◽  
Author(s):  
N. K. Sharma ◽  
M. D. Sarker ◽  
Saman Naghieh ◽  
Daniel X. B. Chen
Keyword(s):  
Cortical Bone ◽  
Linear Regression Analysis ◽  
Tensile Tests ◽  
Uniaxial Tensile ◽  
Loading Conditions ◽  
Stress Strain ◽  
Strain Behavior ◽  
Nonlinear Stress ◽  
Strain Relationship ◽  
Relationship Of

Bone is a complex material that exhibits an amount of plasticity before bone fracture takes place, where the nonlinear relationship between stress and strain is of importance to understand the mechanism behind the fracture. This brief presents our study on the examination of the stress–strain relationship of bovine femoral cortical bone and the relationship representation by employing the Ramberg–Osgood (R–O) equation. Samples were taken and prepared from different locations (upper, middle, and lower) of bone diaphysis and were then subjected to the uniaxial tensile tests under longitudinal and transverse loading conditions, respectively. The stress–strain curves obtained from tests were analyzed via linear regression analysis based on the R–O equation. Our results illustrated that the R–O equation is appropriate to describe the nonlinear stress–strain behavior of cortical bone, while the values of equation parameters vary with the sample locations (upper, middle, and lower) and loading conditions (longitudinal and transverse).

scholarly journals The Influence of Steel Fiber on the Stress-Strain Behavior of Confined Concrete

2019 ◽  
Vol 2 (1) ◽  
pp. 46
Author(s):  
Widayat Amariansah ◽  
Rinda Karlinasari
Keyword(s):  
Peak Stress ◽  
Fiber Reinforced Concrete ◽  
Experimental Results ◽  
Confined Concrete ◽  
Stress Strain ◽  
Conventional Concrete ◽  
Strain Behavior ◽  
Increased Strength ◽  
Lateral Reinforcement ◽  
Strength And Ductility

This paper presents the result of an experimental study of confined concrete to evaluate the stress-strain behavior of fiber-reinforced concrete, which includes strength and ductility. The effectiveness of steel fibers in influencing the stress-strain behavior was also evaluated by creating a conventional concrete as a control specimen. The experimental results showed that there was a decrease in the value of the increased strength of confined concrete (f’cc/f’co) when the compressive strength of the concrete increased. Reducing the spaces of lateral reinforcement spaces will also increase the strength and ductility of confined concrete. The comparison of experimental results with various confinement models shows that there are substantial differences in the peak stress and the descending behavior of confined fiber concrete.

An Elastic Potential for the Nonlinear Response of Unidirectional Graphite Composites

1984 ◽  
Vol 51 (3) ◽  
pp. 546-550 ◽  
Author(s):  
M.-J. Pindera ◽  
C. T. Herakovich
Keyword(s):  
Nonlinear Response ◽  
Fiber Composites ◽  
Elastic Potential ◽  
Experimental Results ◽  
Fiber Direction ◽  
Graphite Fiber ◽  
Stress Strain ◽  
Strain Behavior ◽  
Graphite Composites

An elastic potential is proposed that is capable of modeling the reversible portion of the observed nonlinear response of unidirectional graphite fiber composites. The model includes both the stiffening stress-strain behavior as well as the softening Poisson’s response for loading in the fiber direction. The model is compared with experimental results for Celion 6000/PMR-15 graphite-polyimide.

Some Effects of Water Immersion on the Mechanical Behavior of a Polyimide Film

1994 ◽  
Vol 116 (4) ◽  
pp. 317-319 ◽  
Author(s):  
B. D. Harper ◽  
J. M. Rao
Keyword(s):  
Time Dependence ◽  
Mechanical Behavior ◽  
Room Temperature ◽  
Water Immersion ◽  
Polyimide Film ◽  
Experimental Results ◽  
Stress Strain ◽  
Strain Behavior ◽  
Temperature Creep ◽  
Room Temperature Creep

Absorbed moisture is generally thought to have a plasticizing effect upon the mechanical behavior of polymers. This paper presents some experimental results illustrating the effects of water immersion upon the room temperature creep and stress-strain behavior of a polyimide film. It is shown that immersion in water results in antiplasticization as demonstrated by a significant increase in stiffness and decrease in time dependence. These effects were found to be reversible following thermal conditioning at 300°C.

scholarly journals Stress-Strain Constitutive Material Models for Hybrid Steel Fiber Reinforced Concrete

2020 ◽  
Vol 9 (2) ◽  
pp. 74-82
Author(s):  
Mohammad Jamshidi Avanaki ◽  
Mohammad Abedi ◽  
Abdollah Hoseini
Keyword(s):  
Reinforced Concrete ◽  
Fiber Reinforced Concrete ◽  
Experimental Results ◽  
Engineering Properties ◽  
Experimental Program ◽  
Fiber Reinforced ◽  
Steel Fiber Reinforced Concrete ◽  
Stress Strain ◽  
Bending Tests ◽  
Strain Behavior

Recent advancements in fiber reinforced concrete (FRC) technology has led to the development of fibrous concrete composites, comprised of fibers with different material and/or geometry, commonly known as hybrid FRC. In one type of hybrid FRC composites, advantageous behaviors of fibers of the same material but with different geometries are gathered in a single FRC mix. The aim of this paper is to develop and validate stress-strain relationships for hybrid steel FRC composites. Six different steel FRC mixes are produced and characterization tests are conducted. Cube, cylindrical and beam specimens are produced for each characterization test corresponding to each of the Steel FRC (SFRC) composites. In this regard, an experimental program is performed to determine the basic engineering properties of SFRC composites using standard compressive, splitting tensile and three-point bending tests. The prescribed procedure of the RILEM guideline, originally developed for non-hybrid FRC, is followed using the obtained experimental results to develop stress-strain behavior models for the SFRC mixes. To validate results for the hybrid SFRC composites, numerical simulations of the 3-point bending tests were performed and compared to that of corresponding experimental results. The results indicated that the proposed stress-strain relationships yield acceptable results for characterizing the behavior of hybrid SFRC composites.

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