Processing and Properties of IM7/LARC ™ -RP46 Polyimide Composites

1996 ◽  
Vol 8 (4) ◽  
pp. 491-505 ◽  
Author(s):  
T H Hou ◽  
S P Wilkinson ◽  
N J Johnston ◽  
R H Pater ◽  
T L Schneiderk
Keyword(s):  
Composite Laminates ◽  
Flexural Modulus ◽  
Engineering Properties ◽  
Isomerization Reaction ◽  
Void Content ◽  
Resin System ◽  
Hold Temperature ◽  
Open Hole ◽  
Interlaminar Shear ◽  
Composite Engineering

LARC™-RP46 resin system is a PMR type polyimide and is prepared by replacing methylenedianiline in the PMR-15 composition with 3,4′-oxydianiline. This resin system retains the same processing characteristics as PMR-15 but also offers enhanced fracture toughness. Rheological measurements were conducted on pre-imidized LARC™-RP46 moulding powder subjected to various ramp and hold temperature schemes. Adequate flow properties were found with theoretical (formulated) molecular weight 6 ≤1500 g mol−1. Critical transition temperatures for optimizing the process cycle were identified. They included the resin softening point, the imidization reaction peak, the isomerization reaction peak and the gelation point. Utilizing this information, 1.72 × 10 6 Pa (250 psi) cure cycles were designed for B-staged (dry) and unstaged (wet) prepregs. Composite laminates were fabricated which exhibited excellent consolidation and a void content below 0.1–0.2% as measured by image analysis. IM7/LARC™-RP46 exhibited higher composite mechanical properties than IM7/PMR-15. Short-beam shear strength, flexural strength and flexural modulus were measured at room temperature, 93, 150 and 177 °C. Composite engineering properties were also obtained including longitudinal tension, logitudinal compression, interlaminar shear, short block compression, open hole compression (OHC) and compression strength after impact (CAI). Excellent longitudinal tensile and compressive strengths were obtained and the CAI strength was 40% higher than that for PMR-15. Over 80% retention of all RT strengths were noted at 177 °C.

Experimental study on the effect of stitch arrangement on mechanical performance of GFRP laminates manufactured on a basis of stitched preforms

2011 ◽  
Vol 46 (9) ◽  
pp. 1067-1078 ◽  
Author(s):  
Mateusz Koziol
Keyword(s):  
Shear Strength ◽  
Composite Laminates ◽  
Mechanical Performance ◽  
Flexural Modulus ◽  
Interlaminar Shear Strength ◽  
Direction Parallel ◽  
Stitch Density ◽  
Stitch Length ◽  
Interlaminar Shear ◽  
Flexural Tests

This article presents the results of interlaminar shear and flexural tests of stitched polyester glass fiber laminates in dependence on stitch density and main geometric stitching parameters: stitch length and stitch spacing. Purpose of the study is to work out guidelines and indications for manufacturers of composite laminates who use or who plan to use stitching technique. It was found that stitching significantly improves interlaminar shear strength which increases with stitch density. However, stitching causes deterioration of in-plane flexural properties – the deterioration progresses when stitch density increases. Obtained results indicate that it is better to achieve increase in stitch density (resulting in improvement of interlaminar shear strength) by reduction of stitch length than by reduction of stitch spacing. Stitched laminate shows higher flexural strength and flexural modulus when bent into direction parallel to the stitch lines than when bent into the transverse direction. The results obtained within the study and their approximation constants may be a base for a new theoretical model simulating behavior of stitched laminate during static bending and enabling prediction of its mechanical performance.

Projectile Impact Behavior of Z-Fiber Reinforced Laminar Composites

2012 ◽  
Vol 441 ◽  
pp. 717-725 ◽  
Author(s):  
B. S. Nashed ◽  
J.M. Rice ◽  
Yong K. Kim
Keyword(s):  
Glass Fiber ◽  
Composite Laminates ◽  
Flexural Modulus ◽  
Impact Behavior ◽  
Projectile Impact ◽  
Testing Procedures ◽  
Laminar Composites ◽  
Interlaminar Shear ◽  
Strength And Stiffness ◽  
Strength Retention

The bending toughness, strength retention, resistance to damage and bending stiffness of glass fiber mat, laminar composites under high strain rate impact loading conditions was studied. One of the main disadvantages of laminar composite materials is their poor interlaminar shear strength. Recent work has demonstrated a method of Z-direction reinforcement of these composites using electrostatic flocking techniques improve delamination resistance and fracture toughness without degrading the composites tensile strength or other in-plane properties when loaded quasi-statically. The Z-direction reinforcement is accomplished by electrostatically flocking short fibers perpendicular to and between the composite ply layers. In this study, composite samples were prepared using the flocking method in two fabrication modes by the; so-called Z-Axis wet and Z-Axis dry procedures. In this work, Z-direction reinforced composite panels (including a non reinforced control) that were previously projectile impact damaged were tested using established mechanical testing procedures. Damage areas were quantified and compared using image processing techniques. Three point bending tests were also conducted on these projectile impact damaged panels to determine and compare their bending toughness, strength retention and modulus. The results show that Z-Axis reinforcement by the flocking technique improves the overall mechanical strength and stiffness properties of glass fiber mat laminar composites. For example, Z-Axis reinforced projectile damaged and not damaged glass fiber mat composite laminates are found to have flexural strengths 9% to 15% higher and a flexural modulus (stiffness) 22% to 26% higher than comparable (not Z-Axis flock reinforced) glass fiber mat samples.

Cure kinetics and autoclave-pressure dependence on physical and mechanical properties of woven carbon/epoxy 8552S/AS4 composite laminates

2021 ◽  
pp. 096739112110284
Author(s):  
Abd Baghad ◽  
Khalil El Mabrouk ◽  
Sébastien Vaudreuil ◽  
Khalid Nouneh
Keyword(s):  
Mechanical Properties ◽  
Composite Laminates ◽  
Treatment Time ◽  
Physical And Mechanical Properties ◽  
Cure Kinetics ◽  
Void Content ◽  
Scanning Calorimetry ◽  
Microstructure And Mechanical Properties ◽  
The Matrix ◽  
Interlaminar Shear

The final mechanical properties of composite laminates are highly dependent on their curing cycles in the autoclave. During this cycle, the temperature, pressure, vacuum, and treatment time will influence the quality of manufactured parts. The void content is considered the most harmful defects in carbon/epoxy laminates since they weaken the matrix-dominated mechanical properties such as interlaminar shear and compressive strengths. In the present work, differential scanning calorimetry is used to characterize the influence of time/temperature on the behavior of the epoxy resin. Then, a series of [0/90/−45/+45]s laminates composites are autoclave-cured under various applied pressures to evaluate their impact on microstructure and mechanical properties. The interlaminar shear modulus, interlaminar shear strength, laminate compressive modulus, and laminate compressive strength at room and operating engine temperature were measured. The correlation between microstructure and mechanical properties was also studied. The mechanical properties of manufactured carbon/epoxy laminates are found to be dependent on pressure and microstructure. These results are explored to establish an optimal autoclave pressure route that would minimize porosity without counterbalancing mechanical properties.

IM7/LARCTM-IA polyimide composites

1995 ◽  
Vol 7 (1) ◽  
pp. 105-124 ◽  
Author(s):  
T H Hou ◽  
N J Johnston ◽  
T L St Clair
Keyword(s):  
Mechanical Properties ◽  
Molecular Weight ◽  
High Performance ◽  
Flexural Modulus ◽  
Engineering Properties ◽  
Solvent Resistance ◽  
Polymer Backbone ◽  
Molecular Weights ◽  
Interlaminar Shear ◽  
Langley Research Center

LARCTM-IA (Langley Research Center-Improved Adhesive) aromatic polyimide, based on oxydiphthalic anhydride and 3.4'-oxydianiline, was evaluated as a matrix for high-performance composites. Six poly(amide acid)solutions in N-methylpyrrolidone (NMP), end-capped with phthalic anhydride to various theoretical molecular weights, were synthesized and their molecular weights and molecular weight distributions determined, Importantly, high concentrations of low-molecular-weight species were found in all the offset compositions. Except for the 1% offset polymer, all fully imidized films failed a solvent resistance test which involved immersion in acetone, methyl ethyl ketone, toluene, dimethylacetamide and chloroform for 1 min followed by a fingernail crease. Unidirectional prepreg was fabricated from each of the six resins by both standard drum winding procedures and the LARC multipurpose prepreg machine. The consolidation cycle developed previously for IM7/LARCTM-ITPI composites was found to be equally applicable for IM7/LARCTM-IA composites since both materials are similar and were prepared in and prepregged from NMP. An optimal end-capped resin composition was identified (4% stoichiometric imbalance) by using, as a screening tool, initial composite mechanical properties (short-beam shear strength, longitudinal flexural strength and flexural modulus) at room temperature, 93, 150 and 177°C. Composite engineering properties for the 4% offset composition were obtained, including longitudinal tension, transverse flexural, longitudinal compression, interlaminar shear, short block compression, open hole compression and compression strength after impact. Notably, the CAI strength was 303.2 MPa (44 Ksi) showing that the LARCTM-IA composites have good damage tolerance. A minor modification of LARCTM-IA polymer backbone which did not alter the consolidation cycle, designated as LARCTM-IAX, improved solvent resistance measurably. Mechanical properties of IM7/LARCTM-IAX composites were shown to be comparable to those exhibited by the baseline IM7/LARCTM-IA composites.

On the Relationship between Engineering Properties and Delamination of Composite Materials

1981 ◽  
Vol 15 (4) ◽  
pp. 336-348 ◽  
Author(s):  
Carl T. Herakovich
Keyword(s):  
Finite Element ◽  
Shear Stress ◽  
Composite Laminates ◽  
Strong Influence ◽  
Mutual Influence ◽  
Engineering Properties ◽  
Moisture Expansion ◽  
Interlaminar Shear Stress ◽  
Interlaminar Shear ◽  
The Relationship

The influence of the coefficient of mutual influence, poisson's ratio and coefficients of thermal and moisture expansion on delamination is studied. Engineering theories are compared to finite element and experimental results. It is shown that the mismatch in coefficient of mutual influence can have a strong influence on delamination with fiber angles in the 10°—15° range being critical for adjacent (±θ) layer combinations. The mismatch in coefficient of mutual influence is reduced by a factor of two and the interlaminar shear stress τzx is reduced significantly when the ±θ layers are interspersed between 0° and 90° layers. It is shown how the results can be used for design of composite laminates.

scholarly journals Improving flexural and dielectric properties of carbon fiber epoxy composite laminates reinforced with carbon nanotubes interlayer using electrospray deposition

2020 ◽  
Vol 9 (1) ◽  
pp. 1170-1182
Author(s):  
Muhammad Razlan Zakaria ◽  
Hazizan Md Akil ◽  
Mohd Firdaus Omar ◽  
Mohd Mustafa Al Bakri Abdullah ◽  
Aslina Anjang Ab Rahman ◽  
...  
Keyword(s):  
Carbon Nanotubes ◽  
Dielectric Properties ◽  
Carbon Fiber ◽  
Composite Laminates ◽  
Epoxy Composite ◽  
Flexural Modulus ◽  
X Ray Diffraction ◽  
Electrospray Deposition ◽  
Ft Ir ◽  
Carbon Fiber Epoxy

AbstractThe electrospray deposition method was used to deposit carbon nanotubes (CNT) onto the surfaces of woven carbon fiber (CF) to produce woven hybrid carbon fiber–carbon nanotubes (CF–CNT). Extreme high-resolution field emission scanning electron microscopy (XHR-FESEM), X-ray diffraction (XRD), Raman spectroscopy and Fourier transform infrared spectroscopy (FT-IR) were used to analyze the woven hybrid CF–CNT. The results demonstrated that CNT was successfully and homogenously distributed on the woven CF surface. Woven hybrid CF–CNT epoxy composite laminates were then prepared and compared with woven CF epoxy composite laminates in terms of their flexural and dielectric properties. The results indicated that the flexural strength, flexural modulus and dielectric constant of the woven hybrid CF–CNT epoxy composite laminates were improved up to 19, 27 and 25%, respectively, compared with the woven CF epoxy composite laminates.

Progressive fracture analysis of the open-hole composite laminates: experiment and simulation

2021 ◽  
Vol 262 ◽  
pp. 113628
Author(s):  
Zhaoyang Ma ◽  
Jianlin Chen ◽  
Qingda Yang ◽  
Zheng Li ◽  
Xianyue Su
Keyword(s):  
Composite Laminates ◽  
Fracture Analysis ◽  
Open Hole ◽  
Progressive Fracture ◽  
Experiment And Simulation

scholarly journals Progressive Failure Analysis in Open-Hole Tensile Composite Laminates of Airplane Stringers Based on Tests and Simulations

2020 ◽  
Vol 11 (1) ◽  
pp. 185
Author(s):  
Jian Shi ◽  
Mingbo Tong ◽  
Chuwei Zhou ◽  
Congjie Ye ◽  
Xindong Wang
Keyword(s):  
Failure Analysis ◽  
Composite Laminates ◽  
Progressive Failure ◽  
Tensile Load ◽  
Fiber Failure ◽  
Stress Criterion ◽  
Progressive Failure Analysis ◽  
Analysis Technique ◽  
Open Hole ◽  
Failure Types

The failure types and ultimate loads for eight carbon-epoxy laminate specimens with a central circular hole subjected to tensile load were tested experimentally and simulated using two different progressive failure analysis (PFA) methodologies. The first model used a lamina level modeling based on the Hashin criterion and the Camanho stiffness degradation theory to predict the damage of the fiber and matrix. The second model implemented a micromechanical analysis technique coined the generalized method of cells (GMC), where the 3D Tsai–Hill failure criterion was used to govern matrix failure, and the fiber failure was dictated by the maximum stress criterion. The progressive failure methodology was implemented using the UMAT subroutine within the ABAQUS/implicit solver. Results of load versus displacement and failure types from the two different models were compared against experimental data for the open hole laminates subjected to tensile displacement load. The results obtained from the numerical simulation and experiments showed good agreement. Failure paths and accurate damage contours for the tested specimens were also predicted.

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